How to Split Equity Between Co-Founders: A Framework

The equity conversation is the first real test of a co-founder relationship. Not because the math is hard — it isn't — but because it forces every assumption into the open: who is committing what, who is risking what, and what each person believes the other is worth.

Founders mishandle it in two opposite ways: rushing to "50/50, let's move on" to avoid the awkwardness, or treating the split like a courtroom where every past contribution must be priced. Both store up trouble. Here is the middle path we recommend to teams matching on Foundersbase.

Start with the only rule that is non-negotiable

Whatever you decide about percentages, all founder equity vests. The standard schedule is four years with a one-year cliff: leave in month eleven and you keep nothing; stay past the cliff and a quarter has vested, with the rest vesting monthly.

4 years / 1 year

Vesting is not a sign of distrust. It is the mechanism that makes trust affordable: it converts "what if my co-founder leaves in six months with 40% of my company?" from a company-ending risk into a bounded one. Investors will require it anyway at the first priced round — adopting it on day one simply means you, not your seed investors, chose the terms.

Equal split: the strong default

When two or three founders commit full-time, at the same time, from roughly the same financial position, an equal split is usually right — and it is what a large share of the best-performing founding teams choose.

The argument is forward-looking: over a 7–10 year company life, the work ahead overwhelms any difference in the work behind. An equal split also sets the cultural tone — we are peers, we resolve problems as peers — which compounds in every hard conversation that follows.

Equal splits become the wrong answer when the inputs are genuinely unequal and everyone knows it. Pretending otherwise doesn't avoid the conflict; it schedules it.

When to deviate: the contribution factors that actually matter

If the starting lines differ, adjust for the factors below — and ignore almost everything else.

Two practical notes. First, salary differences are not equity differences: if one founder draws less salary to extend runway, fix it with deferred compensation, not extra points — and when you start paying the team you hire next, treat that as a separate decision covered in salary vs equity for early hires. Second, negotiating skill is not a contribution factor — if your split reflects who argued harder rather than the table above, you have created a fairness debt the relationship will eventually have to repay.

A useful sanity check: each founder writes down independently what split they believe is fair, with one sentence of reasoning per factor. If the numbers land within ten points of each other, you are negotiating details. If they are far apart, you have discovered a misaligned-expectations problem before it became a company problem — which is the trial-project phase doing its job, as described in our technical co-founder playbook.

Put it in writing: the founder agreement

The split is one clause of a document every founding team needs before serious work begins — the co-founder agreement:

1. Equity and vesting

   Percentages, the vesting schedule, the cliff, and acceleration terms (if any) for acquisition or termination scenarios.

2. Roles and decision rights

   Who owns product, who owns commercial, and — most importantly — the tie-break protocol when owners disagree on something irreversible.

3. IP assignment

   Everything built for the company belongs to the company. This clause is the first thing lawyers check in due diligence.

4. Exit ramps

   What happens when a founder leaves voluntarily, is asked to leave, or can no longer work. Defining "good leaver" and "bad leaver" while everyone still likes each other is the whole point.

Have a startup lawyer review the final document. It is a few hundred euros against the single most expensive category of startup failure: founder disputes.

How the conversation should actually go

Schedule it deliberately — mid-trial-project, not after months of work have already diverged. Bring the factor table, not positions. Talk through each factor honestly, write down the numbers, and then stress-test the result with three questions:

1. The four-year test: will the person with less equity still find this fair in year four, when the company is working and the early differences feel ancient?
2. The mirror test: would you accept the other side of this split?
3. The investor test: can you explain this cap table to a seed investor in one sentence without anyone at the table wincing?

If all three pass, sign it and stop thinking about it. The cap table is infrastructure, not a scoreboard — the teams that win treat it that way.