Business · Startup equity
Founder equity split calculator.
Give each factor a weight, score each co-founder, and get a split to start the conversation. Every weight and score is yours. Everything runs in your browser.
With weights of 30 (idea), 30 (time), 20 (cash), 10 (skills) and 10 (risk), and the example scores shown, the split comes out at 58.69%, 30.08% and 11.22% for three founders. On 10,000,000 founder shares that is 5,869,444, 3,008,333 and 1,122,222 shares.
Your numbers
Your result
Fill the form and press Calculate.
How the split is worked out
For each factor, a founder's share of that factor is their score divided by the total of all founders' scores. Their overall share is the weighted average of those factor shares, using your weights. If a factor has a weight but nobody has a score above zero, it is dropped and the remaining weights are rescaled; the result tells you how much weight was ignored.
This is a structured way to put numbers on a conversation between co-founders, not a recommended or standard split. The factors, the weights and the scores are all judgement calls, and the result is only as fair as the inputs. Nothing on this page claims a published standard for how equity should be divided.
Worked example
Weights: idea 30, time 30, cash 20, skills 10, risk 10 (total 100). Scores for Founders 1, 2 and 3: idea 5, 3, 0; time 10, 10, 5; cash 5, 0, 0; skills 8, 6, 4; risk 7, 7, 6. Founder 1 gets 30 x 5/8 + 30 x 10/25 + 20 x 5/5 + 10 x 8/18 + 10 x 7/20 = 18.75 + 12 + 20 + 4.44 + 3.5 = 58.69. Founder 2: 11.25 + 12 + 0 + 3.33 + 3.5 = 30.08. Founder 3: 0 + 6 + 0 + 2.22 + 3 = 11.22. Divided by 100 and applied to 10,000,000 shares, that is 5,869,444, 3,008,333 and 1,122,222 shares (rounded; the total can differ from 10,000,000 by a share or two).
Limits
The calculator does not account for roles that change over time, for founders who leave, or for how much each factor should be worth later. Stock that is given to founders is often subject to vesting, which this calculator does not apply (use the vesting schedule calculator). How shares are issued, taxed and documented is a legal and tax question; see a lawyer and an accountant before agreeing a split.
Sources, opened 8 October 2026: no external source is cited for the split: the method is arithmetic on weights and scores you enter. For how vesting is commonly described, see Wikipedia, Vesting.
Frequently asked questions
How do you split equity between co-founders?
There is no single correct method. One approach is to weight the factors that matter to you (time, cash, idea, skills, risk), score each founder, and use the weighted result as a starting point for discussion. This calculator does that arithmetic.
Do the weights have a standard?
No. The weights and scores are entirely yours, and this page does not cite a published standard for them.
What if one factor has no scores?
A factor with a weight but zero scores for every founder is dropped and the other weights are rescaled. The result shows how much weight was ignored.
Should founder shares vest?
Many founders agree to vesting on their own shares, but that is a decision for you and your lawyer. Use the vesting schedule calculator to see the effect.
Is an equal split safer?
An equal split is simple but not automatically fair. Compare it with the weighted result to see where your views differ, then agree on a split together.
Educational only. Not legal, tax or investment advice.
Planning and learning aid only. Real terms depend on the signed documents and your jurisdiction. Tax treatment (409A valuations, 83(b) elections, ISOs and similar) is left to a qualified professional. Amounts are in any one currency; the symbol is only a label.