Why "let's just split it equally" is where partnerships go to die.
A 50/50 handshake feels fair on day one. Two years in, when one founder went full-time and the other kept a job, when one put in the cash and the other brought the idea, that equal split quietly turns into resentment — and resentment, not the market, is what kills most startups.
The fix isn't a harder conversation. It's a structured one: weigh what actually matters to your company, score each founder out loud, and let the math propose a split. Then protect it with vesting so nobody walks away with a full stake for a few months' work, and see what dilution does to you all when you raise. This tool runs that math — every number is shown, nothing leaves your browser.
- Equity split
- Who owns what percentage of the company at the start.
- Vesting
- Earning your shares over time (standard: 4 years, with a 1-year "cliff" before any vest). Protects everyone if a founder leaves.
- Dilution
- Every time you raise money, you sell a slice — so everyone's percentage shrinks.
- Decision rights
- Who is accountable for which decision, so a disagreement doesn't freeze the company.
Your founding team
What should matter — and how much
Score each founder — together
Optional: the private gut-check
Each founder enters the split they feel is fair, ignoring the model. We compare it to the computed split and flag the biggest gap — the number to talk about first.
Vesting & your next round
Who decides what?
The split is the easy part. Living with it is the hard part.
These numbers are a fair starting point — not a signed agreement. Before you lock vesting, a buy-back, and decision rights into a real founder agreement, get a second read from someone who has sat on the company side of these deals. Then take it to a lawyer.
Get a second read →How the math works (for the curious)
The split. Each founder's weighted contribution is C = Σ (weight × score ÷ 10) across the dimensions you set. Their share is C ÷ total C. We show it beside two reference points: a plain equal split, and a "criticality-only" split (who is hardest to replace).
Vesting. Vested fraction at month m is m < cliff ? 0 : min(m, years×12) ÷ (years×12). A leaver keeps grant × vested fraction; the unvested remainder is cancelled and re-allocated to the founders who stay, pro-rata.
Dilution. New investors take raise ÷ (pre + raise). The option pool is created before the money (the standard, founder-diluting case), so every existing holder is scaled by (1 − investor% − pool%). Exit take-home is final % × exit value, before liquidation preferences.
What it doesn't cover. Liquidation preferences, multiple priced rounds, secondary sales, and tax. It shows the shape of a fair deal — not your official cap table or legal advice.
Decision support and negotiation starting points — not legal, tax, or financial advice. A fair split is a judgment call; this tool structures it and does the arithmetic, but the numbers depend entirely on the scores and weights you enter. Agree them honestly, and take the result to a lawyer before you sign. Nothing leaves your browser. Logic current as of June 2026.