The prompt
Score 10 of 10, Excellent
Use it when You need a defensible estimate of how big a market is for a plan, pitch or investment case, built from customer counts and prices, not a headline number.
- {{audience}}
- {{product}}
- {{market_definition}}
- {{figures}}
- {{assumptions}}
- {{horizon}}
Full prompt and why it works
Prompt
Build a bottom-up estimate of the market for the product below, for {{audience}}, so that every number in the estimate can be traced and challenged. The aim is a range we can defend, not the largest number we can justify. The product and who buys it: {{product}} The market to size (customer type, geography, time period): {{market_definition}} Figures we have, each with its source and date (customer counts, industry statistics, prices, our own sales data): """ {{figures}} """ Assumptions we already hold, if any: {{assumptions}} Use these headings: 1. The calculation: a step-by-step chain from the number of potential customers to annual spend, such as the number of businesses of the right type, times the share that has the problem, times what they would pay per year. Show each step as a line with the figure, its source and the running result. 2. Three levels, if the figures allow: everyone who could use the product (total market), those we can serve with our current product and channels (serviceable market), and what we could realistically win in {{horizon}} (obtainable share), each with its own assumptions. 3. Low, base and high cases: a table with the columns Input, Low, Base, High, Source or reason, and the resulting totals. 4. Sensitivity: the two inputs that move the result most, and by how much. 5. Weakest links: the assumptions with the least support, and how to check each one, such as a survey question or a cut of our sales data. Keep it under 700 words, not counting the tables. For example, the form of one line in the chain: "Dental practices in the region: 4,200 (national business register, 2024). Running total: 4,200." This shows the form only; use the real figures. A good estimate lets a skeptical reader change one assumption and recalculate the result. Use only the figures above, and mark every number you did not get from them as an assumption, with your reasoning. Do not use a top-down figure from an industry report as a check unless it is in the figures, and do not round up to a nicer number. If a step in the chain has no figure, write [figure needed: what it is and where it might come from] and carry the calculation forward with the step marked, rather than inventing a number.
Variables
- {{audience}}
- Who will read the estimate, for example "investors in our seed round" or "the strategy committee".
- {{product}}
- What you sell and to whom, in a sentence or two.
- {{market_definition}}
- The market to size, for example "independent dental practices in the US, annual software spend".
- {{figures}}
- Every figure you have, each with its source and date: counts, statistics, prices, your own conversion and sales numbers.
- {{assumptions}}
- Assumptions you already use, for example "30% of practices still book by phone", or "none".
- {{horizon}}
- The period for the obtainable share, for example "three years".
Why it works
- What good looks like. Every step shows its figure, source and running total, so a skeptical reader can change one assumption and recalculate.
- If unsure. A step with no figure gets a marked placeholder and is carried forward, instead of being filled with an invented number.
- Length. Low, base and high cases and the two most sensitive inputs show how wide the range really is.