About the Cofounder Equity Split Calculator
This cofounder equity split calculator turns a difficult conversation into a structured one. Choose how many founders you have (two to four), decide how much each type of contribution matters to your company — the idea and any IP, cash invested, time commitment, role and responsibility, and expertise and network — and then score each founder from 0 to 10 on each. The calculator converts those scores into an ownership percentage and a share count for each founder.
It is meant for founding teams at the very start, before incorporation or before signing a founders’ agreement, and for teams revisiting a split when someone joins later. Because every weight and score is visible, each founder can see exactly why the split comes out the way it does, and you can test how sensitive the answer is to the assumptions you disagree on.
The result is a starting point for negotiation, not a verdict. Many teams end up close to an equal split when everyone commits full time from day one, and almost every team protects the split with vesting (commonly four years with a one-year cliff) so equity follows the work that is actually done.
How to use the cofounder equity split calculator
- 1Choose the number of founders and the total founder shares to allocate.
- 2Agree weights for each factor based on what will drive this company’s success.
- 3Score each founder from 0 to 10 on every factor, ideally independently first, then discuss.
- 4Review the suggested split and the factor table to see what drives any difference.
- 5Adjust weights you disagree on to test sensitivity, then document the result with vesting.
Formula and method
Each factor gets a weight reflecting how much it matters to this particular company (the defaults favour ongoing commitment over the original idea). Within a factor, the weight is shared among founders in proportion to their scores, so a founder who scores 10 when the other scores 5 takes two-thirds of that factor’s weight.
Each founder’s equity is the sum of their points across all factors divided by the total weight used. Weights do not need to add up to 100 — they are normalised — and a factor where every founder scores 0 (or with a weight of 0) is ignored. Share counts are equity percentage × the founder shares to allocate, rounded to whole shares.
- Weight(f)
- Importance of factor f (idea, cash, time, role, expertise)
- Score(i, f)
- Founder i’s 0–10 score on factor f
- Equity(i)
- Founder i’s share of the founder equity
Worked examples
Two full-time founders, one brought the idea
Founder A takes 8/12 of the 10-point idea weight, half the cash and time weights, 9/15 of the role weight and 6/14 of expertise: 6.67 + 7.5 + 17.5 + 12 + 8.57 = 52.24 points out of 100, or about 52.2%. Founder B ends at about 47.8%, close to an even split, and the 10M founder shares divide 5,223,810 to 4,776,190.
Three founders, one part-time
Adding a part-time third founder who scores 3–5 on each factor takes about 21.5% of the equity. Founders A and B are diluted proportionally on every factor, with A still ahead because of the idea and the CEO role.
Equal scores give an equal split
When both founders score the same on every factor, each takes half of every weight, so the split is exactly 50/50 and each receives 5,000,000 shares.
Frequently asked questions
Should cofounders always split equity equally?+
Not always, but an equal or near-equal split is common when all founders join at the same time, commit full time and share the risk. Large differences are easier to justify when contributions really differ, such as one founder working part time or investing significant cash.
How much should the idea be worth in an equity split?+
Usually less than founders expect. Execution over many years creates most of the value, so the idea is often weighted lightly unless it comes with real IP, a working product or proprietary relationships.
Should the CEO get more equity?+
Many teams give the CEO a modestly larger stake for the extra responsibility of fundraising, hiring and accountability to the board, but it is not a rule. The role factor in this calculator lets you decide how much that responsibility should count.
What happens if a cofounder leaves early?+
Without vesting, a departing founder keeps all their shares. A vesting schedule — commonly four years with a one-year cliff — lets the company repurchase unvested shares, which protects the remaining founders and makes any split far less risky.
How do I account for cash invested by one founder?+
You can score it in the cash factor, but large amounts are often better treated as a separate investment, for example a SAFE or convertible note on the same terms an outside investor would get, so the founder split reflects work rather than money.