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 unless you sign in to save.
- 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 →This check, run continuously with your data
Connect your real cap table once, and this ownership math stays live: grants, vesting, dilution and decision rights, tracked as they change.
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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.