Two founders, one laptop, a shared Notion board, and a conversation they keep postponing: who gets what. I've sat in on that conversation more times than I'd like to admit, and I've watched it go badly in almost every way it can. One founder walked away with 45% after a year of full-time work while the other kept 55% for an idea sketched on a napkin and three investor intros. That company died fourteen months later.
So let's talk about how to set a fair equity split among cofounders without the false comfort of "we'll figure it out later." Because you won't. You'll figure it out in a lawyer's office at 11pm, or you won't figure it out at all.
Key takeaways
- There is no universal formula, but there is a repeatable process: define contributions, weight them, then put them in writing.
- 50/50 works only when the work stays roughly equal — and it rarely does.
- Vesting is not optional. It is the single cheapest insurance policy you'll ever buy.
- Late cofounders should get less than founding cofounders, and that's not unfair — it's arithmetic.
- Whatever you decide, decide it in the first month, not the sixth.
How to set a fair equity split among cofounders (and stop arguing about it)
Fairness has nothing to do with feelings and everything to do with a shared scoring model that you both agree on before you score anything. That's the whole trick. Once you're negotiating percentages, you've already lost. When you're negotiating the criteria that produce a percentage, you can actually have a rational conversation.
Here's the structure I use now, after getting it wrong twice.
The weighted contribution grid
List the things that actually build this company, then assign a weight to each. Percentages must sum to 100. A typical weighting looks like this:
- Idea and initial validation — 10%
- Full-time commitment going forward — 30%
- Domain expertise and network — 20%
- Capital contributed — 15%
- Sales and fundraising ability — 15%
- Technical execution — 10%
Then each founder scores themselves and the other on each line, from 1 to 10. Take the average of your self-score and their score of you. Multiply by the weight. Sum. Normalize to 100%.
Sounds mechanical? It is. That's the point. The moment numbers replace adjectives ("I'm obviously doing more"), the temperature in the room drops about twenty degrees.
And here's the part nobody mentions: the grid will surprise you. In one case I watched, a founder who'd assumed she was the junior partner ended up with 58% because her sales pipeline and network outweighed her colleague's codebase work. Nobody argued. The spreadsheet did the arguing.
What the numbers usually look like
Most two-founder teams land somewhere between 60/40 and 70/30 — not 50/50. Roughly a third of the teams I've observed went perfectly even, usually because both founders quit their jobs on the same week and had comparable experience. The teams that skewed hardest were the ones where one person was part-time.
Which brings up an obvious problem.
Should cofounders be 50/50 equity?
Only if you can answer one question: what happens when one of you stops showing up? Equal equity means equal votes, equal payouts, and — the part people forget — equal deadlock. Two 50% shareholders with a disagreement have no tiebreaker. None. A 50/50 company is one bad quarter away from a stalemate that a lawyer will bill you six figures to untangle.
That said, I won't tell you 50/50 is wrong. I've seen it work beautifully, three times, in teams where both founders had genuinely interchangeable skills and wrote a deadlock clause into the shareholders' agreement on day one. It's not the split that kills companies. It's the split without a mechanism.
Should cofounders be 50/50 or 51/49?
Go 51/49 when you need a decider and can't stomach a formal deadlock procedure — it's the bluntest tool in the box, and it works. Go 50/50 when you want enforced consensus and you're prepared to write down exactly how you break ties (a mediator, a shotgun clause, an odd-numbered third board member). What you should never do is drift into 50/50 by default because you were too polite to have the conversation.
How much equity should a co-founder keep?
Enough to stay motivated through a down round, and not so much that you have nothing left to hire with. In practical terms: founding teams should hold 70–85% of the cap table after the first round, and the ESOP you set aside for early hires is the line item people underestimate most. A 10% option pool sounds generous until you realize it's your third engineer and your head of sales, full stop.
If you're the solo-heavy founder — the one who dragged this thing off the ground alone — keeping 70–80% for yourself going into the first raise is not greedy. It's standard. What is greedy is keeping that percentage while your cofounder works the same hours for 4%.
What about a late cofounder?
Someone joining nine months in, after the product exists and the first customers have paid, is not a founding cofounder. They're a very early employee with a founder title. The fair range is 2–10% depending on what they bring and how much risk they're taking on — with full vesting, always.
I made this mistake early on: gave 25% to a friend who joined at month eight because I felt guilty about the timing. He left at month fourteen. His shares didn't. It took a repurchase agreement and eight weeks of awkwardness to clean that up.
Vesting: the tool that actually makes any split fair
A split is a snapshot of an assumption. Vesting is what makes the assumption survivable when reality diverges. Standard terms, and I'd argue these are non-negotiable:
- Four-year vesting, monthly or quarterly. Industry default, and for good reason.
- One-year cliff. Nobody keeps anything before twelve months. Brutal? Yes. Protective? Absolutely.
- Reverse vesting for founders — your shares are issued up front but subject to repurchase until they vest. Tax treatment varies by jurisdiction, so talk to an accountant, not me.
- Acceleration on change of control — single or double trigger. Discuss it now, while you like each other.
| Scenario | Typical split | Vesting | Watch out for |
|---|---|---|---|
| Two equal cofounders, full-time from day one | 50/50 or 55/45 | 4 years, 1-year cliff | Deadlock clause is mandatory |
| Technical + commercial, comparable commitment | 60/40 | 4 years, 1-year cliff | Who owns IP? Get it assigned in writing |
| One part-time founder | 70/30 or 80/20 | Standard plus milestone | Part-timer's shares should vest slower |
| Late cofounder, month 9 | 2–10% | 4 years, no acceleration | Don't call them a cofounder in the cap table |
| Three founders | 40/35/25 or 45/30/25 | 4 years, staggered cliffs | Two against one is a real risk |
How to divide shares between three partners
Three is the hardest number. With two founders, you have a relationship. With three, you have a political system, and every pair can outvote the third. My honest advice: run the same weighted grid, but score each founder independently and in silence, then compare. Group scoring in a room of three turns into a coalition game within ten minutes.
Also stagger the cliffs. If all three founders vest on the same date, you get a single moment where your entire founding team could walk out together — theoretically. Nobody does that, but the optics to an investor are lousy, and the ones who've seen a cofounder triangle implode will ask about it.
Putting it in writing (and what happens when you don't)
Founders' agreement, IP assignment, vesting schedule, deadlock clause. Four documents. Every founder signs all four before anyone quits their job. If a cofounder resists signing — that's your answer about the cofounder.
The split you choose today is a guess. The paperwork is what lets you correct the guess without a lawsuit. Get it done in week one, then get back to work.
