Co-Founder Equity Split Calculator
Weight the factors that matter to your company, rate each founder on them, and get a split. It uses Frank Demmler's published Founders' Pie method, with capital contribution added — and it produces a starting point for a conversation rather than a verdict.
Free · No signup · Runs entirely in your browser
This co-founder equity split calculator uses Frank Demmler's Founders' Pie method: weight each factor for how much it matters to your company, rate each founder on it, and the percentages fall out. It produces a starting point for a conversation, not a verdict — which is how Demmler intended it to be used.
How much does each factor matter here?
How much the original concept matters here. 0–10.
Turning it into something fundable. 0–10.
Experience and contacts in this market. 0–10.
Full-time, and what was given up to be here. 0–10.
Money in. Not part of the original method.
Rate each founder, 0–10
| Factor | ||
|---|---|---|
| Ideaweight 5 | ||
| Business planweight 4 | ||
| Domain expertiseweight 7 | ||
| Commitment & riskweight 9 | ||
| Capital contributedaddedweight 3 | ||
| Weighted score | 197 | 194 |
This comes out essentially even. That is a legitimate result when contributions really are equal — the objection to 50/50 is to reaching it by avoiding the conversation, not to the number itself.
Whatever you land on, vesting matters more than the split. Four years with a one-year cliff is the convention, and it is what protects everyone if a founder leaves in month seven — which is the scenario that actually breaks cap tables.
The split matters less than the vesting schedule behind it. If you are building the product largely on your own, Tekk turns what you want into specs your coding agent can actually execute.
The method
This is Frank Demmler's Founders' Pie Calculator, taught at Carnegie Mellon and the most widely cited structured approach to the problem. Three steps:
- Weight each factor 0–10 for how much it matters to this company
- Rate each founder 0–10 on each factor
- "Multiply each of the founder's values by the factor's value... Add up the numbers for each founder, sum those totals and determine the relative percentages."
That is the whole calculation. Its value is not the arithmetic — it is that it forces two separate conversations that usually get tangled: what matters here, and who did it.
The factors
| Factor | The question | Source |
|---|---|---|
| Idea | Whose original concept was it? | Demmler |
| Business plan | Who turned it into something fundable? | Demmler |
| Domain expertise | Who brings the experience and contacts? | Demmler |
| Commitment & risk | Who is full-time, and gave up most to be here? | Demmler |
| Capital contributed | Who is putting money in? | Added here |
The fifth is an addition and is labelled as one. Demmler's method predates the norm of founders writing cheques into their own company, and the tool ranking #1 for this search says outright that it does not handle "co-founders who invest significant cash".
Worked example
Weights: idea 5, business plan 4, expertise 7, commitment 9, capital 3.
| Factor | Weight | Founder A | Founder B |
|---|---|---|---|
| Idea | 5 | 9 → 45 | 3 → 15 |
| Business plan | 4 | 7 → 28 | 5 → 20 |
| Domain expertise | 7 | 4 → 28 | 9 → 63 |
| Commitment & risk | 9 | 10 → 90 | 8 → 72 |
| Capital | 3 | 2 → 6 | 8 → 24 |
| Total | 197 | 194 | |
| Share | 50% | 50% |
A had the idea and works harder at it; B knows the market and funded it. On these weights they come out even — but they arrived there by comparing five specific things rather than by flinching from the conversation, and that is a materially different 50/50.
Change one weight and the answer moves. If domain expertise mattered more than commitment in this market, B is ahead. That sensitivity is a feature: it shows you which disagreement actually matters.
What the number does not settle
Vesting matters more. Four years with a one-year cliff. It is what protects everyone if a founder leaves in month seven, which is the scenario that genuinely wrecks cap tables — far more often than a split being a few points off.
Later joiners do not fit. The method assesses everyone at one moment. Someone joining after the product ships is better handled with a smaller stake and a standard option grant than by retrofitting ratings.
Nor does the option pool. Investors will expect 10–20% set aside, usually created pre-money, which means it comes out of your side rather than theirs. It dilutes founders proportionally, so it does not change the ratio between you — but it does change what the number means.
And it is not advice. This is arithmetic that structures an argument. Take the output to a lawyer, who will care about share classes and the founder agreement rather than the percentages.
How it works
- 1
Weight the factors for your company
Idea, business plan, domain expertise, commitment and risk — Demmler's original four — plus capital contributed. Score each 0–10 for how much it matters here. A deep-tech company and an agency will weight these very differently, and that is the point.
- 2
Rate each founder
Everyone gets 0–10 on every factor. This co-founder equity split calculator multiplies each rating by its factor weight, adds them up per founder, and takes the relative percentages. Up to five founders, though past three the conversation usually matters more than the arithmetic.
- 3
Sanity-check the result
Demmler's own advice, and the right advice. If the number surprises you, the disagreement is really about the weights or the ratings — which is a far more productive argument than one about percentages, because it is about facts rather than feelings.
Frequently asked questions
- How do you split equity between co-founders?
- There is no formula that settles it, but there is a method that structures the argument. Frank Demmler's Founders' Pie Calculator weights each contributing factor for how much it matters to the specific company, rates each founder on each factor, then multiplies and totals. The percentages are the relative totals, which is what the co-founder equity split calculator above computes.
- Is a 50/50 split a bad idea?
- Not inherently — the objection is to reaching it by avoiding the conversation. If two founders genuinely contribute equally, an even split is the honest answer and this co-founder equity split calculator will produce it. What is dangerous is defaulting to 50/50 because discussing the difference feels awkward, and then living with the resentment for four years.
- What factors should count?
- Demmler's four are idea, business plan preparation, domain expertise, and commitment and risk. A fifth — capital contributed — is added here because founders putting real money in is common now and the original method does not cover it. The #1 result on this search explicitly does not handle it either.
- Should the idea count for much?
- Usually less than the person who had it thinks. Ideas are cheap relative to execution, and weighting the idea factor above about 5 tends to produce a split the other founders quietly resent. If you are the idea founder, argue for your weight on commitment instead — it is the more defensible case.
- How do I handle a founder who joins later?
- Poorly, with this method — and that is a limitation worth naming. A weighted-factor split assumes everyone is being assessed at the same moment. A founder joining after the product ships is usually better handled with a smaller stake plus a standard option grant, rather than by trying to backfill ratings.
- What about a founder who is part-time?
- Rate them lower on commitment and risk, which is exactly what that factor is for. But be careful: a part-time founder who later goes full-time will expect the split to reflect it, and renegotiating equity is far harder than setting it. Vesting handles this better than the percentages do.
- Does this account for vesting?
- No, and vesting matters more than the split. Four years with a one-year cliff is the convention, and it is what protects everyone when a founder leaves in month seven — which is the scenario that actually wrecks cap tables. Agree the vesting schedule in the same conversation as the percentages.
- What if one founder ends up with most of the company?
- The tool flags it above 70%. That can be the correct answer, but check whether the minority founders will still be around in three years. A co-founder holding single digits has effectively been made an early employee, and will often behave accordingly — which may be fine, provided everyone knows that is what happened.
- Should we leave room for an option pool?
- Yes, and it dilutes founders proportionally, so it does not change the ratio between you. Investors typically expect a pool of 10–20% before a priced round, and they will usually want it created pre-money — which means it comes out of the founders' share rather than theirs. Worth knowing before the term sheet.
- Can a co founder equity split calculator replace a lawyer?
- No. It is arithmetic that structures a conversation. The output of any co founder equity split calculator is a number to take to a lawyer, not a substitute for one — and founder agreements, vesting schedules and share classes all need drafting properly.
- What if we cannot agree on the ratings?
- Then you have learnt something more valuable than a percentage. Disagreement about ratings is disagreement about what each person has contributed and will contribute, and discovering that now is much cheaper than discovering it after incorporation. Work through the gap before you work through the split.
- Do you store what I enter?
- No. The calculation runs entirely in your browser. Nothing is sent to a server, nothing is logged, and there is no account — which seems worth stating on a page where you type honest assessments of your co-founders.
- Why is this free, and what is Tekk?
- Tekk is a spec-driven development platform for people building software with AI coding agents. This calculator costs us nothing to run, and the founders arguing about a split are usually the same people building the product. No signup, no run limit, no upsell inside the tool.
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