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Co-founder equity split calculator: a fair split you can explain
Equal splits are the default and the most common source of founder breakups. Score each founder on idea, commitment, capital, skills, execution and risk, weight the criteria, and get a split with the reasoning written down.
| Criterion (weight) | Founder 1 | Founder 2 |
|---|---|---|
Idea, IP and early work Who brought the insight and what was built before the team formed | ||
Time commitment Full time from day one scores 5; evenings and weekends 1 or 2 | ||
Capital invested Cash put in or salary forgone, relative to the others | ||
Critical skills and experience How hard it would be to replace this person | ||
Risk and opportunity cost What each person gave up to be here | ||
Leadership and responsibility Who carries the company externally and makes the hard calls |
Why not just split equally?
Equal is easy and feels fair on day one. It stops feeling fair when one founder goes full-time and the other does not, or when one founder’s skill turns out to be the company. Investors ask how you decided; “we didn’t discuss it” is a weak answer.
The six criteria
The idea and early work, time commitment and salary sacrifice, cash invested, scarce skills, execution so far and personal risk taken. The weights are adjustable: a deep tech company weighs skills more, a sales-led one weighs execution more.
What matters more than the split
Vesting. Four years with a one-year cliff protects everyone, including the founder who stays. A founder who leaves after six months with 40 percent kills the next round. Decide the split, then put vesting and a leaver clause in the founders’ agreement.
How to run the conversation
Each founder scores everyone, including themselves, separately. Compare the results and discuss the differences, not the final number. Write down the reasoning and revisit it only at clear milestones.
Questions founders ask
What if one founder put in money?
Treat cash as a loan or a SAFE at a fair cap rather than equity, so the split reflects work.
Should the CEO get more?
Only if the CEO scores higher on commitment, execution and risk. The title alone is not a criterion.
Can we change the split later?
Yes, with everyone’s agreement, before the first outside round. After that it is expensive and visible.
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