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Market Share Calculator

Calculate a share, record what it refers to, export it, then test how far it moves. All in your browser.

Calculate a share

Calculation method

240

1,000

Measurement basis

The unit selector only labels the output. A number carries no unit, so the tool cannot distinguish turnover from tonnes. Check the unit before relying on the result.

Market share

24%

s
market share — the result, in percentage points
x
the undertaking's revenue
X
total market revenue
100
turns the ratio into percentage points
24%
76%
The undertaking 24%Rest of the market 76%

A market share is an input to a competition assessment, not a conclusion.

What that means in practice

What this figure does and does not tell you

A market share is an input to a competition assessment, not a conclusion. It only becomes meaningful once the relevant product and geographic market has been defined, and it is read alongside entry barriers, buyer power and how closely the firms actually compete. As an order of magnitude, the Turkish Competition Authority's guidelines on horizontal mergers treat shares above 50% as capable of indicating a dominant position. This can indicate dominance but does not establish it.

Source: Guidelines on the Assessment of Horizontal Mergers and Acquisitions · Turkish Competition Authority · Türkiye · 4 May 2026 · para. 17

Need this figure to hold up in a filing or an investigation? KFD advises on merger control and dominance in Türkiye.

The practical question

How to find the market share of a company

The arithmetic is the easy half. The work is deciding what the market is and finding two figures that genuinely belong to it. Six steps, and the trap that catches people at each one.

  1. Decide what the market is

    Before any division, fix three things: which products a customer would switch to, where they would shop for them, and over what period. A full financial year is the usual choice because it absorbs seasonality. If a competition authority has already defined a market in the same sector, its published decision gives you a boundary you can cite instead of inventing one.

    The trap. Choosing the boundary after seeing the answer. Write the definition down before you calculate — the calculation record below has a field for exactly this.

  2. Find the undertaking's own figure — the numerator

    Audited annual reports and financial statements come first; investor presentations often restate the same numbers by product line. For a diversified group, the operating-segment note (IFRS 8) is what you want, not the consolidated total. Listed Turkish companies file on the Public Disclosure Platform (KAP); regulated ones also report to their sector regulator.

    The trap. Using group turnover for a company that also sells outside the market you defined. The numerator must cover the same products and geography as the denominator.

  3. Find the market total — the denominator

    This is the hard half, and there are four routes. Sector regulators publish market statistics (in Türkiye: BTK for telecoms, EPDK for energy, BDDK for banking). Trade associations publish registrations and shipments. National and European statistical offices publish structural business statistics. And published competition authority decisions frequently state the size of a market and the shares in it.

    The trap. Taking a published total at face value. Ask what it excludes — imports, own-label supply, online channels and small producers are the usual gaps, and every one of them inflates your share.

  4. Build it bottom-up when no total exists

    If nobody publishes a total, sum what the main participants report themselves and add a residual for the rest. The “Other” row in the calculator above exists for this: it holds the part of the market you could not itemise, so the named shares are not overstated.

    The trap. Leaving the residual empty. Then your list is treated as the whole market and every share comes out too high.

  5. Make the two figures comparable

    Numerator and denominator must use the same measure (value, volume or capacity), the same period, the same geography and the same corporate perimeter. A number carries no unit, so nothing in the tool can catch a mismatch — that check is yours.

    The trap. Dividing revenue by units, or a calendar year by a fiscal year. Both produce a number that looks perfectly reasonable and is meaningless.

  6. Calculate, record it, then try to break it

    Run the figures through the calculator, record the scope and the source alongside the result, then use the sensitivity tests further down: what if the total misses suppliers, what if the market were defined more narrowly, what if the estimate is off by 15%. A share that survives those is one you can defend.

    The trap. Reporting a single number to two decimal places when the denominator is an estimate. Precision is not accuracy.

Where the market total actually comes from

Five routes to a denominator. In practice you use more than one and see whether they agree — two independent totals that land close together are worth more than one precise-looking figure.

Sources for the market total, what each gives you and its limitation
SourceWhat it gives youWhat to watch
Sector regulator statisticsSubscriber, volume or revenue totals for regulated markets, usually quarterlyOnly covers licensed activity; unregulated substitutes fall outside
Trade and industry associationsRegistrations, shipments or production for their membersNon-member and importer volumes may be missing entirely
National and European statistical officesStructural business statistics by activity code, comparable across countriesActivity codes rarely match a competition-law market exactly
Published competition authority decisionsA market definition and often the shares the authority acceptedTied to the date of the decision; markets move
Company reports, added upA bottom-up total you can trace to named sourcesNeeds a residual for everyone you could not itemise

Whichever route you take, write it down. A share whose denominator has no stated source cannot be checked by anyone — which is why the calculation record below asks for it before you export.

The mathematics

Read the formula

There are only three moving parts, and almost every mistake in a market-share figure is a mistake about one of them.

Market share is one undertaking's activity, divided by the activity of the whole market it competes in, expressed as a percentage.

xi

Undertaking's activity

the undertaking's revenue

X

Total market activity

total market revenue

si

Market share

the result, in percentage points

x

The numerator

Today: the undertaking's revenue.

Your value

240

Breaks when it covers a different product set, a different legal entity or a different period from the denominator.

X

The denominator

Today: total market revenue.

Your value

1,000

Breaks when the market is drawn too narrowly, too broadly, or when suppliers inside it were never counted.

× 100

The scaling

Turns a ratio into percentage points.

Your value

24%

It does not affect the calculation, but it hides the ratio that contains the economics.

Choosing between value, volume and capacity

The basis decides what “activity” means

The arithmetic is identical for all three. The answer is not: the same undertaking can hold 12% of the litres sold and 25% of the money spent. Whichever you choose, use it for every figure in the calculation and state which measure it is.

Value shareselected
Price and quantity together. The usual choice where products are differentiated or priced very differently.
Volume share
Physical presence, ignoring price. Suits homogeneous products sold in comparable units.
Capacity share
Ability to supply rather than what was actually supplied. Used where output is constrained by capacity.

Methodological basis: The choice of share metric and the identification of market participants are set out in the 2023 US Merger Guidelines methodology.

Why value and volume disagree

Revenue is price times quantity. Move either slider and watch the two measures separate: an undertaking selling fewer, dearer units can lead on value and trail on volume in the same market.

r
revenue — what a value share is built from
p
price per unit
q
units sold

Volume counts the 100 on its own. Value counts the product. Two different questions, two different shares.

Formula sheet

Every formula on this page

Seven relations, each one line. The right-hand column evaluates them against the figures you entered above, so the symbols and your own numbers stay side by side.

Show all seven formulas

Market share

si
market share of undertaking i
xi
that undertaking's sales, units or capacity
X
the same measure, for the whole market
100
turns the ratio into percentage points

One undertaking's activity over the activity of the whole market, as a percentage.

With your figures24%

Share from a set of undertakings

si
market share of undertaking i
xi
the row you are reading
Σxj
the sum of every row you entered — your denominator

When you list the participants instead of a published total, the denominator is the sum of the rows. It represents the whole market only if you listed every participant.

With your figuresSwitch to “Several undertakings”

Correction for a missing market

s*
corrected share, after the missing market is added back
s
the share you first calculated
u
the fraction of the true market your total misses (0 to 1)

If your total misses a fraction u of the real market, the honest share is the reported one scaled down by that fraction, rather than reduced by u percentage points.

With your figuresu = 12% → 21.12%

Change in share over time

Δln
change in the natural logarithm — a growth rate, near enough
s
market share — the result, in percentage points
x
the undertaking's activity at each date
X
the market total at each date

Share follows the gap between the two growth rates. Growing slower than the market means losing share while getting bigger.

With your figures-4.45 log points

Herfindahl-Hirschman Index

H
the Herfindahl-Hirschman Index itself
Σ
sum over every undertaking in the market
si
share of undertaking i, in percentage points

Squaring rewards size, so the index reacts to who holds the shares, not just how many players there are.

With your figuresNeeds a list of undertakings

Four-firm concentration ratio

CR4
combined share of the four largest undertakings
s(i)
shares ranked largest first, so (1) is the biggest undertaking

The combined share of the four largest undertakings. Simpler than HHI and blind to how those four compare with each other.

With your figuresNeeds a list of undertakings

Effective number of undertakings

Neff
how many equally-sized undertakings the market behaves like
H
the Herfindahl-Hirschman Index itself
10,000
the HHI of a pure monopoly (100² ), so the ratio reads as a count

Reads an HHI back as a number of equal-sized undertakings. At 2,500, a market behaves like four undertakings of the same size.

With your figuresNeeds a list of undertakings

Comparative statics

What happens if you change it

Four one-step changes, all calculated from the 24% above. Apply any of them to load the new figures into the calculator.

The undertaking sells 10% more

Numerator × 1.10, denominator unchanged.

26.4%

+2.4 pp

The share moves one-for-one with the numerator: +10% in, +10% out.

The market turns out 10% bigger

Denominator × 1.10, numerator unchanged.

21.8%

−2.18 pp

Not −10%. Dividing by 1.10 costs 9.1% of the share because changes in the denominator do not pass through symmetrically.

Everyone grows 10%

Numerator and denominator × 1.10.

24%

0 pp

Nothing happens. A share is a ratio, so it is blind to the scale of the market it sits in.

The relevant market is defined 20% narrower

Denominator × 0.80, numerator unchanged.

30%

+6 pp

A 20% narrower market is a 25% higher share. Market definition moves the number more than most business facts do.

The rule underneath all four

In percentage terms, a share moves with the gap between how fast the numerator grows and how fast the denominator grows. Nothing else. The same rule explains every card above and the growth experiment further down.

%Δ
percentage change in the quantity that follows
s
market share — the result, in percentage points
x
the undertaking's activity — the numerator
X
total market activity — the denominator

Exact in logarithms: Δln(s) = Δln(x) − Δln(X). The approximation is close enough for changes under roughly 20%.

Where a share breaks

Four sensitivity tests

Four ways the same arithmetic produces a different answer. Open the ones that matter to your case. Each runs on the figures you entered above, and each result is carried into the calculation record.

1The denominator is a legal choice, not a factMarket definition sets the denominator. Move the boundary and watch the same undertaking take three different shares.

Fewer substitutes count as competing. Total: 600 USD million.

More substitutes or a wider geography count. Total: 1,400 USD million.

Same undertaking, same sales, three defensible answers spanning 22.86 percentage points. This is why a market-share argument is usually a market-definition argument.
Broad market17.1%
Your market24%
Narrow market40%same undertaking, smaller denominator

The nested boxes show conceptual scope, not geography. A narrower market is not a smaller country. It is a shorter list of things a customer would switch to.

Methodological basis: Product and geographic boundaries are drawn from demand-side substitution. See the European Commission's 2024 Notice on the definition of the relevant market.

2What if the market total is incomplete?Published totals miss importers, own-label supply and small producers. Anything missing inflates the share, always in the same direction.

Coverage test

Your total then represents 88% of an estimated true market of 1,136 USD million.

24%

Reported

21.1%

Corrected

+2.88 pp

Upward bias

The identity is worth memorising: corrected share = reported share × (1 − u). Missing 12% of the market does not cost 12 percentage points. Instead, it costs 12% of the share. On a large share that is a lot; on a small one it is almost nothing.
Show the derivation
X*
estimated true market total, once the missing part is added
Xobs
the market total you entered — the observed part
u
the fraction of the true market your total misses (0 to 1)
s*
corrected share, after the missing market is added back
s
the share you first calculated, against the total you entered
x
the undertaking's activity — unchanged by any of this
X*
estimated true market total, once the missing part is added
u
the fraction of the true market your total misses (0 to 1)

How wide is your uncertainty?

Coverage error has a direction. Estimation error does not have a direction; it gives you an interval. If two credible sources put the market this far apart, the honest output is a band, not a point.

Market between 850 and 1,150 USD million.

Resulting market-share range

20.9% to 28.2%

Central estimate 24% · width 7.37 pp

0%100%

The arithmetic on this page is exact to four decimal places. That precision says nothing about whether the denominator is right. Precision is routinely mistaken for accuracy in exactly this spot.

Methodological basis: Coverage and estimation error are treated as statistical-quality questions in Statistics Canada's Survey Methods and Practices.

3A growing undertaking can be losing shareShare is relative, so it says nothing about whether a business is growing. Set the two growth rates and watch them fight.

24%

Share at t₀

23%

Share at t₁

−1.04 pp

Change

Verdict

It grew but still lost share.

The undertaking moves up by 10% while the market moves up by 15%. The share follows the 5-point gap against the undertaking, not either rate on its own.

Δln
change in the natural logarithm — a growth rate, near enough
s
market share — the result, in percentage points
x
the undertaking's activity at each of the two dates
X
the market total at each of the two dates

With your figures: -4.45 log points

This is why competition authorities look at how shares have moved over several years rather than a single snapshot: a stable share in a fast-growing market is a very different fact from a stable share in a stagnant one.

4From one share to market structureA single share cannot tell you whether the rest of the market is one strong rival or forty weak ones.

This experiment needs a list of undertakings

Concentration is a property of a distribution, not of one number. Switch the calculator to “Several undertakings” and enter the participants. Alternatively, load the worked example and come straight back here.

Reference

Method, rules and questions

How it works

“Single undertaking” divides one undertaking's sales by total market sales. “Several undertakings” treats everything you enter as the whole market and derives each share from that total. If you have not entered the whole market, every share comes out too high. The “Other” row accounts for the missing share.

Methodology

Market share = the undertaking's value / total market value × 100. The arithmetic is the same whichever unit you use, but the answer is not: a share of sales value and a share of units or volume measure different things, and the same firm can hold 12% of the litres sold and 25% of the money spent. Pick the measure that best reflects competitive strength in the market you are analysing, use it for every figure in the calculation, and keep every figure within the same period. What the resulting share means legally depends first on how the relevant product and geographic market has been defined.

Rules the calculator applies
  • Inputs must be non-negative, and the undertaking's value cannot exceed a positive market total.
  • In “Several undertakings” mode the values entered are treated as the whole market, so the shares always add to 100%.
  • Rounding differences are absorbed by the largest share, so a set of equal shares still sums to exactly 100%.
  • Numerator and denominator must use the same unit and the same period. The tool cannot detect a mismatch.
  • Concentration measures are computed from named undertakings only; the residual row is reported separately.

Frequently asked questions

Should I use sales value, units or volume?

It depends on what the measure is meant to show. Value shares, calculated on turnover, capture willingness to pay and are the usual choice where products are differentiated or priced very differently. Volume shares (units, tonnes, litres or subscribers) capture physical presence and suit homogeneous products. Capacity shares are used where output is constrained by capacity. Whichever you choose, state it: a share with no stated basis cannot be checked by anyone reading your work.

Can revenue and units be mixed in one calculation?

No. Every figure in a calculation must use the same unit of measurement and cover the same period. The tool cannot detect a mismatch because a number carries no unit; the unit selector only labels the output.

What does a market share actually mean legally?

On its own, very little. A share is one input into an assessment: it is read together with how the market was defined, entry barriers, buyer power, how closely the firms compete and how stable shares have been over time. A high share can indicate a dominant position under Article 6 of Law No. 4054, and combined shares are among the first things examined in merger control. In both settings, a share is where the analysis starts, not where it ends.

Where do I find the figures to put in?

The tool holds no market data; you supply it. In practice the total is built from published sources: audited annual reports and investor presentations of the main players, sector regulators' statistics, industry association figures, and the market descriptions set out in published Turkish Competition Board decisions in the same sector. Record the source and the period next to each figure. A share is only as defensible as the total underneath it.

Can I transfer the result to the HHI tool?

Yes, in one click, and the figures never leave your browser. One caution: the HHI squares every row, so an aggregated “Other” row inflates the index. Use the transfer to carry the named firms' shares across, then delete or break up the “Other” row before relying on the HHI figure.

Why is there an “Other” row?

To hold the part of the market that belongs to firms you have not listed. Leave it empty and the tool has no way of knowing the market is larger than your list, so it treats your firms as the whole market and every share comes out too high. Treat the row as a residual bucket rather than a competitor: it is not a single undertaking and must not be handled as one.

Take it with you

Record it so it can be checked

A percentage on its own cannot be checked by anyone. Say what market it refers to, then take the record with you. It carries the scope, the inputs, the assumptions you test below and the sources.

Scope of the calculation

These four fields do not change the percentage. They are what make it checkable later, so they travel with every export.

Generated Pending · calculation version MARKET-SHARE-2

Product market
Not stated
Geographic market
Not stated
Period
Not stated
Source of the market total
Not stated
Calculation type
Single undertaking
Measurement basis
Value share
Unit of measure
USD million
Numerator
240 USD million
Denominator
1,000 USD million
Market share
24%

Worked formulas

Every relation you ran, with your own numbers substituted. This is the part that travels into all three exports.

Market share

x
the undertaking's revenue = 240 USD million
X
total market revenue = 1,000 USD million

Correction for a missing market

s*
corrected share, after the missing market is added back
u
the fraction of the true market your total misses (0 to 1)

Narrower market definition (−40%)

X
the denominator under this candidate market definition

Broader market definition (+40%)

X
the denominator under this candidate market definition

Market-total uncertainty (±15%)

X
the market total at each end of the plausible range
Assumptions carried into the record
  • Missing-market test: 12% of the true market assumed unobserved → 21.12%
  • Market-total uncertainty: ±15% → 20.87% to 28.24%
  • Narrower definition (−40%) → 40%; broader (+40%) → 17.14%

No scope recorded yet, so every export will read “Not stated”. Filling the four fields above takes a few seconds and is what separates a number from evidence.

The CSV carries a header block naming the tool, its version and the scope. Printing produces this record sheet only, not the rest of the page. Nothing leaves your browser.

What each export contains

All three are built from the same record, in your browser. Nothing is uploaded.

Plain-text record — for an email, a case note or an assignment

Fixed 72-column layout so it survives being pasted anywhere. Carries the scope, the inputs, every worked formula, the assumptions and the sources.

Preparing…
Excel workbook — a working model, not a frozen table

Two sheets. The inputs sit in their own cells and every share, sensitivity test and concentration measure is a live formula pointing at them — change the market total in Excel and the whole sheet recalculates. Shares are computed with =B15/B16*100, HHI with =SUMPRODUCT(C3:C6,C3:C6), and the residual row is deliberately left out of HHI and CR4.

CSV — for importing the numbers somewhere else

Values only, no formulas. Opens cleanly in any tool; spreadsheet formula injection is neutralised on the way out.

Preparing…
Printed document / PDF — for a file or a bundle

Printing produces this section only, on a KFD masthead, with the result, the worked formulas typeset as equations, the inputs table and the sources. The rest of the page is not printed.

Your inputs are processed in your browser and are not sent to KFD servers. This tool is provided for general informational purposes only and does not constitute legal advice. Results are based on the information you enter, on the legislation in force as at the last reviewed date shown in the tool, and on the assumptions stated explicitly. The circumstances of a specific case may require a different assessment.

References

Every source this page relies on

Last reviewed: 20 August 2026

A market share is measured the same way everywhere; what changes between jurisdictions is the threshold at which it starts to matter. All 10 references are listed below — the Turkish instruments that govern how a share is read, and the methodology sources behind how one is calculated: the European Commission, the US agencies, the UK Competition and Markets Authority, the Turkish Competition Authority, Eurostat and Statistics Canada. The same list travels into every export.

Turkish statutory instruments

Competition-law methodology

Market definition

Concentration and business statistics

Statistical methodology

Where to go next

A share on its own rarely settles a question. These are the usual next steps, and every page behind them is free to use:

KFD Consulting

Where this calculation ends up

A market share is rarely the point. It is the first line of a merger filing, a dominance assessment or a compliance review. It is also the line the other side attacks first. KFD Consulting is a competition law practice in Ankara that argues these questions in front of the Turkish Competition Authority.

Competition law services KFD Consulting homeContact