How to Calculate Market Share: Formula, Data Sources and Examples

Market share is your revenue divided by total revenue in your market, expressed as a percentage. Earn $12M in a market worth $400M and your share is 3%.

The formula takes a second. Finding a defensible number for that $400M is the actual work, and it is the part most explanations skip. This covers the three ways to measure share, where the total-market figure comes from when nobody publishes it, and how to track the number over time without a data subscription.

What is market share?

Market share is the portion of a defined market that one company holds, measured over a fixed period.

It answers a comparative question that absolute revenue cannot: growing 40% sounds excellent until you learn the market grew 60% and you lost ground. Share strips out the market's own movement and tells you whether you are winning.

The word "defined" is carrying weight there. A market share figure is only as meaningful as the market boundary behind it, and that boundary is a choice you make.

The market share formula

Market share (%) = (Your revenue ÷ Total market revenue) × 100


The unit-based form replaces currency with volume:

Market share (%) = (Your units sold ÷ Total market units) × 100


Both need the same period and the same geography on each side. Mixing your trailing twelve months against an analyst's calendar-year market figure produces a number that means nothing, and the error is invisible once it reaches a slide.

Revenue share, unit share and customer share

Three denominators, three different answers about the same business.

Revenue share — your revenue over market revenue. The default, and the right one for most commercial questions, because it reflects what the market actually pays you.

Unit share — your volume over market volume. Useful in categories with comparable products and meaningful price variation. A premium vendor can hold 20% revenue share on 6% unit share; a discounter the reverse.

Customer share — your customers over total buyers in the market. This is market penetration rather than market share, and the distinction matters enough that it has its own article. Use it when customer count drives the business model more than contract value.

Pick one and label it. "We have 12% market share" with no qualifier is a claim nobody can check, including you next quarter.

Where the total market number comes from

This is the section that decides whether your share figure is credible. There are four routes, in descending order of reliability.

1. Public filings. In concentrated markets where the large players are listed, sum their reported segment revenue. This is the most defensible source because it is audited, but it has two limits: segment reporting is often coarser than your actual market, and private competitors are invisible.

2. Analyst and trade-body reports. Gartner, IDC, industry associations. Usable, and usually the figure everyone else in your market is quoting — which has its own value, since a shared denominator makes comparisons meaningful even if the absolute is imperfect. Check the market definition before adopting the number; analyst market boundaries rarely match how a company defines its own market.

3. Bottom-up construction. Build the market from countable units. Number of potential buyers × average contract value. This is the method to use when no published figure fits your segment, and it has a real advantage: you control every assumption and can defend each one. It is also the method most likely to be wrong, because a small error in average contract value multiplies across the whole base.

If you are building bottom-up, you are calculating total addressable market — the same exercise, from the other direction. We have covered how to calculate TAM separately, and the sizing logic there applies unchanged here — as well as why most TAM figures cannot be acted on.

4. Triangulation. Build the figure two ways and compare. A bottom-up estimate within 20% of an analyst figure gives you reasonable confidence in both. A 3x divergence tells you the two are measuring different markets, and you need to work out which one matches the business.

What to avoid: taking a headline market size from a press release or a vendor's marketing page. Those figures are usually the broadest possible definition, chosen to make an opportunity look large, and building your share on them will understate your position by an order of magnitude.

Worked example: a B2B software market

Most market share explanations use Nike, Tesla or Spotify, where the market figure is published and the arithmetic is trivial. Here is the harder and more common case.

A company sells compliance software to mid-market financial services firms in the US. No analyst report covers that segment precisely. Building bottom-up:

InputValueSourceUS financial services firms, 200–2,000 employees18,400Census business patternsShare with a compliance software budget62%Industry survey, 2025Addressable firms11,40818,400 × 0.62Average annual contract value$34,000Own closed-won data, 24 monthsTotal market revenue$387.9M11,408 × $34,000Company revenue$12.4MOwn accountsMarket share3.2%12.4 ÷ 387.9

Now sanity-check it. The three largest competitors report or are estimated at roughly $95M, $60M and $41M in this segment. Those three plus this company account for $208M — 54% of the estimated market. The remaining 46% spread across a long tail of smaller vendors and in-house builds is plausible for this category. The estimate survives.

Had that check produced 140%, the market definition would be too narrow or the average contract value too high, and the number would need rebuilding rather than reporting.

Relative market share and why it changes the read

Absolute share tells you your slice. Relative share tells you your position.

Relative market share = Your share ÷ Largest competitor's share


At 3.2% against a leader on 24.5%, relative share is 0.13. Any figure below 1.0 means you are not the leader, and the distance tells you how far off.

This matters because absolute share moves for reasons that have nothing to do with you. A market that grows 30% while you grow 25% shows falling share and rising revenue. Relative share against a named competitor is a cleaner read on whether you are gaining ground on the company you are actually competing with.

Tracking share over time without a data subscription

Most companies calculate market share once, for a fundraise or a board pack, then never again — because the underlying market figure is expensive to refresh.

Proxy indicators can track direction between proper recalculations. None of them measures share. All of them correlate with it.

• Competitor headcount, from public profiles. Sales headcount in particular tracks revenue with a lag in most B2B categories.
• Job postings. A competitor opening fifteen sales roles is telling you something about their next four quarters.
• Review volume on category sites. New reviews per quarter is a rough proxy for new customers per quarter across a comparable set.
• Branded search demand. Relative search volume between you and named competitors, which is directional for consideration rather than revenue.

Be honest about what this is: a trend line, not a measurement. The error bars are wide and the correlation breaks whenever a competitor changes strategy. Use it to notice that something has moved, then rebuild the real number properly.

Common mistakes

Mismatched periods. Your trailing twelve months against a calendar-year market figure. Always the same window on both sides.

Geography drift. Company revenue includes international sales; the market figure is domestic. Either restrict revenue to the geography measured or find a matching market figure.

Calling your segment the market. The narrower the definition, the higher the share — which is why "market leader" claims so often come with a heavily qualified market. It is not dishonest to define your market narrowly, but the definition has to hold up when someone else applies it.

List price against discounted revenue. Building market size from list prices while measuring your own revenue net of discounts overstates the market and understates your share, sometimes by 20% or more.

What to do with the number

Define your market in one sentence and write it down next to the figure. Recalculate properly once a year, and track proxies in between. Then look at relative share against your closest named competitor, because that is the number that tells you whether you are winning.

A share figure without its market definition attached is not a metric. It is a claim.

If share is flat because you are invisible to the buyers you have not reached yet, that is a demand problem before it is a product one — which is where enterprise SEO does its work.