How to Size Your Market From the Bottom Up, Not a Report
How to size your market from the bottom up: count real buyers, price each one honestly and multiply. Smaller than an industry report, and far more believable.
To size your market from the bottom up, count how many organisations of your type exist, estimate what each would plausibly pay you, and multiply. The number is smaller than an industry report's, and far more believable, because it proves you know who buys.
Size your market from the bottom up: the sum, not the story
Here's the slide every investor has seen a thousand times. A giant global figure. Then the line: "if we capture just one percent."
Nobody believes it. Experienced investors don't even read it. They glance, note that you've not thought about who actually buys, and move on.
That is the top-down market size. It starts with an industry report and shrinks it by an assumed share. It tells the room nothing about your customer. Worse, it can't survive the obvious follow-up: "Who exactly are these people?"
To size your market the bottom-up way, you start with the people. How many exist, what each would pay, what that adds up to. It's a smaller number and a much stronger slide. And you can do it this week, on your own, with no analyst.
The three-line sum
Three lines. That's all the method is.
- Count the buyers. How many organisations or people of exactly the type you serve exist in the places you can actually reach?
- Price each one. What would each plausibly pay you, per year, for what you really sell?
- Multiply. Buyers times price. Show the arithmetic on the slide.
Each line has a trap. Each trap is where investors poke.
Line one: counting the buyers
Be ruthless about the definition. "Small businesses" is not a buyer. "Independent dental practices in the countries where I can invoice and support" is a buyer. The tighter the definition, the easier it is to find a real count from a public register, a trade body or a directory.
If you can't find a count, say how you estimated. A rough count with the method shown beats a precise-looking figure with no source.
And ask the awkward question: how many of those could buy from you today? Not in a future where you've translated the product into six languages. Today, with what you have.
Line two: pricing each one
Use what you charge, or what you've tested charging. Not what the biggest competitor's enterprise tier costs. If you have paying customers, you already hold the most honest figure in the deck: what real people paid.
If you have no customers yet, you have no price evidence, and the slide should admit it. "I've not sold this yet, here is how I will find out" costs far less credibility than a price pulled from the air.
Line three: the multiplication
Put it on the slide as a sum a stranger can follow. Buyers, price, total. Three numbers and two symbols. If it needs a diagram and two paragraphs, you haven't finished the thinking.
Free guide · 23 pagesClarity is the signal.The Pitch Playbook: what investors are assessing and how to make it easy to say yes or no.Get the free guide →Top-down against bottom-up
When you size your market, the difference is not style. It's what each approach proves.
| Top-down | Bottom-up | |
|---|---|---|
| Starting point | An industry figure | A count of real buyers |
| Your share | Assumed, usually a tiny round percentage | Not needed; the total comes from the sum |
| What it signals | You haven't thought about who buys | You know your customer |
| Size of the result | Huge and unconvincing | Smaller and believable |
| Survives "who exactly?" | No | Yes |
| Where the work is | Finding a report | Thinking about your customer |
That last row is why people skip it. The report takes ten minutes. The sum takes thought. Thought is the thing being assessed.
What if the bottom-up number is small?
It might be. Sit with that for a moment, because it matters more than the slide.
Investors who back businesses for a fund want an ending large enough to return that fund. If your honest sum comes out modest, there are two possible readings. Either your definition of the buyer is too narrow and there's an adjacent group you could reach, or the market really is small.
If it's the first, widen with evidence. Show the adjacent group, show why they'd buy, and be clear that it's a stretch rather than today. If it's the second, you've learned something worth more than any pitch: this may not be a business that needs, or suits, outside money.
And that's fine. You own all of it today and answer to nobody. A market that comfortably supports a profitable one-person business is a good market for you, even if it will never interest a fund. A fast, well-reasoned no from an investor tells you exactly that. It is not a verdict on your business. It's a verdict on fit, which is a different fact. If you want to know how that plays out in practice, the post on what investors look for in a pitch explains why they're underwriting risk, not admiring your product.
Say it out loud before you put it on a slide
Try this on a Monday morning. Take a blank page. Write your customer in one specific sentence. Write where you'd find a list of them. Write what you charge. Do the sum.
Now explain it to someone who has never heard of your business. Watch where they frown. That frown is the question an investor will ask, and you've just found it for free.
This is also the quiet benefit of the exercise. People regularly discover their weakest link while preparing to raise: a market claim that dissolves under a single question. Better to meet that question at your kitchen table than across a meeting room.
Where the sum goes once you size your market
It belongs on the market slide, in the standard position, in plain view. Not buried in an appendix. The appendix is for the detail: the sources of your counts, the price tests, the adjacent groups. The main slide carries the three lines and the total.
Keep it a single point per slide. If the market slide also tries to show competitors and a growth forecast, it will do none of them well. The wider structure is covered in what goes in a pitch deck.
One more habit. Replace every adjective on that slide with the evidence behind it. "Massive", "huge", "fast-growing" are all adjectives. A count, a price and a product are evidence.
Free assessmentHow trapped are you, really?Take the Corporate Suffocation Index, the free solopreneur readiness assessment.Take the assessment →The four questions that test your sum
Before the slide leaves your hands, put the sum through the questions an investor would ask. They are not clever. They are the obvious follow-ups, and the bottom-up version answers all of them.
- Who exactly is the buyer? If your answer is a category, tighten it until you could find one on a list.
- Where did the count come from? A register, a directory, your own estimate with the method shown. Never "an analyst said".
- Why would they pay that? Point at what your customers already pay, or at the test you ran.
- What would make the total wrong? Name the weakest of your three lines yourself. It is the same move as naming your biggest risk, and it earns the same trust.
If you can answer all four without reaching for the deck, the sum is ready. If you stumble on one, you've found the work for this week.
Why this suits a one-person business
Here's the thing most founders miss. Doing this well is easier for you than for a big company.
You talk to your customers directly. You know who they are, what they asked for and what they grumbled about. A team of ten loses that. You haven't. The person who has lived the problem and knows who pays for it is describing a real group of people, not a spreadsheet cell. That's why the sum comes naturally to you, and why it reads as credible when you present it.
Use it. Say who the buyers are the way you'd describe a friend's job. The room can feel the difference between that and a figure copied from a report. It is also the thread that links to your traction slide: the customers you already have are your first evidence that the count is real and the price holds.
Free guide · 23 pagesClarity is the signal.The Pitch Playbook: what investors are assessing and how to make it easy to say yes or no.Get the free guide →What not to do
- Don't start with a global figure and slice it. Start with a person.
- Don't count buyers you couldn't serve today.
- Don't borrow a competitor's price because it makes the total bigger.
- Don't hide the arithmetic. If you can't walk through it, you can't defend it.
- Don't treat a small total as a failure. Treat it as information.
Each of those is a failure of research when you size your market, not of storytelling. Both are in your control before the first meeting.
Free assessmentHow trapped are you, really?Take the Corporate Suffocation Index, the free solopreneur readiness assessment.Take the assessment →Frequently asked questions
Why do investors distrust top-down market sizing?
Because it starts from an industry figure and an assumed share, which says nothing about who actually buys. Experienced investors read it as a sign you haven't thought about your customer.
What if I can't find a count of my buyers?
Estimate it and show how. A rough count with the method visible is more credible than a precise-looking number with no source behind it.
Should my market number be big?
It should be true. A smaller figure you can defend beats a huge one you can't. If the honest total is modest, that tells you something about whether outside money fits.
Do I need this if I never raise?
It's still useful to size your market even if you never raise. Knowing how many buyers exist and what they'd pay is the same thinking that decides where to put your hours.
The full method, with the checklists, is in The Pitch Playbook, a free 23-page playbook.
How trapped are you, really?
Take the Corporate Suffocation Index, the free solopreneur readiness assessment.