How To Calculate Market Share

There are only three ways to grow your business - new product or service development, line extensions or growing your market share.

Most businesses don't know how to identify their market share, but I'm happy to show you how I do this for my clients.

It's a three-step process.

1. identify the competitors in your market
2. find out what their turnover is.
3. Compare your share of market % with the rest of the market.

If you're in a small category and you know who your competitors are, you can jump straight to step two. Otherwise my advice is to use AI, such as ChatGPT. Bing Copilot or Perplexity.

You can put in your company name or web address and ask it to list direct competitors or ask it to find a list of companies within your category. I'd suggest both, and make sure you use all variations of what your category might be referred to.

And a tip, you don't need all of your competitors large and small for this to be valuable. A good chunk of the category will be enough to show you where you sit and who is outperforming the rest.

For step two you can actually search the Companies House site for financial reports to gain insights on turnover. Some AI tools, such as Perplexity, will search multiple sources for you but I'm a big fan of Pomanda. It searches all the available sources and where it can't find an absolute number is able to provide a reasonably accurate estimate.

Finally, stick it all in excel and create a pie chart.

That's it.

You now know how much market share you have and how much room for growth there is.

A good marketer can then use that insight to build a solid and focused marketing strategy and plan, generating sales and growing market share over time.

Right. The Obvious Questions Answered.

Why does it matter what our market share is?

Because without it, growth is just a number with no context.

If revenue is up 10% but the category grew 30%, you're losing ground. If revenue is flat but the category contracted 20%, you're actually winning. Market share tells you how you're performing relative to the opportunity available, which is the only number that really describes commercial progress.

It also tells you how much room you have left to grow, which category players you're taking share from and which are taking it from you, and where a realistic growth strategy should be focused. Growth conversations without market share data are mostly guesswork with a spreadsheet attached.

Isn't market share really complicated to calculate?

Not as complicated as most people assume.

Three steps: identify the main competitors in your category, find their approximate turnover (Companies House works for UK businesses, and tools like Pomanda aggregate financial data from multiple sources), and calculate your share as a percentage of the total. Stick it in a pie chart. Done.

You don't need every competitor, and you don't need perfectly accurate turnover figures to the last pound. A reasonable picture of the category is enough to understand where you sit and how much headroom exists. Good enough beats not knowing by a considerable margin.

What are the three ways to actually grow a business?

New product or service development, line extensions into adjacent categories, or growing your share of an existing market.

Most growth conversations focus on the first two because they feel exciting: new products, new markets, new offers. But growing market share in a category you already understand, with customers you already know, against competitors you've already mapped, is usually the most efficient and lowest-risk route available to an established business. Most businesses have more headroom in their existing category than they realise. They just haven't looked at the numbers.

How do we use market share data in our marketing planning?

As the commercial foundation for everything that follows.

Once you know your share, your category size, and where your share is growing or declining, you can connect marketing investment to share of voice and model the expected impact on share of market over time. That relationship, excess share of voice leading to share of market gain, is one of the most empirically solid findings in marketing effectiveness research.

It means you can go to a board and say: at this level of investment and this share of voice, we should expect to grow market share by this amount over this period. That's a forecast, not a hope. Boards respond very differently to forecasts than they do to hope dressed up in a deck.

Our competitors don't publish their financial information. How do we estimate their turnover?

Several ways, and you only need to be approximately right.

For UK companies, Companies House filings include turnover for most limited companies above a certain size threshold, though many smaller companies file abbreviated accounts. Tools like Pomanda, Creditsafe or Beauhurst pull from multiple sources and provide estimates where direct figures aren't available.

For businesses that don't file publicly, you can triangulate from employee count, job postings, physical footprint, and any public statements about growth. It's imprecise, but in combination it gives you a working estimate that's materially better than nothing, and enough to identify roughly where your market share sits.