Founder Equity Calculator
Split it fairly, then build something useful.
Set how much each founder drives the work — the split updates live.
The split above flows straight into the projections below — how it dilutes from Seed to Series D on real Carta 2026 medians, how vesting protects it, and what each founder’s stake is worth at a decacorn exit.
What the split becomes: Seed → Series D
Carta 2026 medians · founders’ fully-diluted %Hardware, aerospace, energy, robotics — the Alumni Founders audience. Capital-heavy, so founders dilute fastest.
| After each round | Seed | Series A | Series B | Series C | Series D† |
|---|---|---|---|---|---|
| Founder A50% today | 25.2% | 15.3% | 8.3% | 5.5% | 5.7% |
| Founder B50% today | 25.2% | 15.3% | 8.3% | 5.5% | 5.7% |
| Founding team | 50.4% | 30.5% | 16.5% | 11.1% | 11.4% |
† Carta does not publish a Series D median split by domain; the blended median (11.4%) is shown for that column.
Typical range · blended 10th–90th percentile
= Deep tech / physical founding-team median · vertical tick = blended median. Half of all teams land inside the shaded 25th–75th spread; the outer numbers are the 10th–90th.
The whole cap table · blended median, all sectors
The employee pool overtakes founders around Series C; investors cross 50% between A and B. The per-founder table above tracks the selected domain; this stack is the blended composition (a slightly different Carta cut), so the founder row won’t match to the decimal.
Is each round worth it? · Paul Graham’s equity equation
Giving up n is only worth it if it makes the remaining slice worth more than the whole was before — the round has to grow the company by more than 1 ÷ (1 − n).
Option-pool shuffle
A post-money pool is created after the round prices, so its dilution is shared across everyone — the neutral, founder-friendly default. Flip to pre-money to see the hit founders absorb when the pool is carved the other way.
Protect it with vesting
Recommended for every founder — including youThe percentage matters far less than whether it’s earned. More than 25% of two-founder teams lose a co-founder within four years. Vesting is what returns an early-leaver’s unearned equity to the company instead of letting it walk out the door. The market standard is 4-year vesting with a 1-year cliff and double-trigger acceleration.
| If they leave, this returns to the company | Leaves before yr 1 | Leaves after yr 2 | Leaves after yr 3 |
|---|---|---|---|
| Founder Agrant 50% | 50%of co. | 25%of co. | 12.5%of co. |
| Founder Bgrant 50% | 50%of co. | 25%of co. | 12.5%of co. |
Double-trigger means acceleration needs two events — an acquisition andthe new owner terminating the founder — so vesting can’t be dodged by a friendly sale. Without vesting, a founder who quits in month two keeps their entire stake for a “free ride.” None of this changes today’s split; it decides who actually keeps it.
If it becomes a decacorn
Founder dollars at a target exitDrag to a target exit valuation. Founders keep diluting at scale — Carta’s median founding team holds just 16.4% once a company is worth $1B+. Even so, the dollars dwarf the founding-day argument.
At a $1B+ post-money, Carta’s median founding team holds 16.4% — together worth $1.6B.
A smaller slice of a huge outcome beats a big slice of nothing. At $10B, five points of the founding split is worth $82M— real money. But a co-founder demotivated into leaving takes far more than five points with them. Don’t torch the partnership over the split; build something worth diluting into, and let vesting protect it.
Projections track Carta’s 2026 Founder Ownership Report medians for a typical company — your rounds, pool sizes, and terms will differ. This tool is guidance, not legal, tax, or financial advice. Document any agreement and have a lawyer paper the final terms.
▸Methodology, vesting & sources
How the numbers are built
The splitis contribution-based. Every factor carries a fixed, visible weight that sums to 100 — the three core execution categories (engineering, product, and sales / biz-dev) dominate at 26 points each, while the original idea is worth just 5, because a startup’s worth is created over the next 7–10 years, not on day one. Rate how much each founder does, and the tool normalizes the scores into a live split, with a one-off slider for a final manual nudge.
The dilutionengine is not a toy simulation: each founder’s projected stake at a round is their split multiplied by Carta’s median founding-team ownership at that stage, for the sector you pick. The percentile band shows the same figure as a range, and Paul Graham’s equity equation flags whether each round is even worth taking — a round pays off only if it grows the company by more than 1 ÷ (1 − n), where n is the fraction sold.
Why vesting matters more than the split
The exact percentage matters far less than whether it is earned. On a standard four-year schedule with a one-year cliff, a co-founder who leaves in month two keeps nothing, and one who leaves after two years keeps only half — the rest returns to the company and the founders who stayed. Given that more than a quarter of two-founder teams lose a co-founder within four years, vesting is the single most important protection on the cap table, which is why every investor requires it.
Questions founders ask
- How should co-founders split equity?
- Start from an even split — it is the honest prior, and the split investors read as a healthy sign. Only about 42% of two-founder teams split exactly evenly, but because a startup’s value is built over the next 7–10 years, small day-one differences rarely justify a lopsided split. When contributions genuinely differ, weight them by role: this calculator scores each founder on engineering, product / design, and sales / biz-dev (the heavily weighted execution work), plus original vision, fundraising, CEO leadership, and prior-founder experience — with the idea itself deliberately weighted low. It does that math live and flags any split past 60/40 as a red-flag zone worth a second look.
- Should co-founders always split equity 50/50?
- Not always, but near-equal is usually right. An even split signals trust and keeps both founders motivated for the long haul. Once one founder holds more than about 60%, splits start to correlate with co-founder conflict — YC’s red-flag zone. A bigger slice is worthless if a demotivated co-founder sinks the company, so deviate only for a real, durable difference.
- How much equity do founders keep after each funding round?
- On Carta’s 2026 blended medians, a founding team holds about 56% after Seed, 36% after Series A, 23% after Series B, 16% after Series C, and 11% after Series D. Deep-tech and hardware founders dilute faster — roughly 50% / 31% / 17% / 11% through Series C — because they raise more capital. The employee option pool overtakes founders around Series C, and investors cross 50% between Series A and B.
- What is founder vesting and why do you need it?
- Vesting means each founder earns their equity over time instead of owning it outright on day one. The market standard is four-year vesting with a one-year cliff (nothing vests in the first year, then it accrues monthly) plus double-trigger acceleration. It matters because more than a quarter of two-founder teams lose a co-founder within four years — vesting returns an early-leaver’s unearned shares to the company instead of letting them walk out the door. It does not change the agreed split; it decides who actually keeps it.
- What is the option-pool shuffle?
- When investors require an employee option pool to be created before their money goes in (a “pre-money” pool), that dilution comes almost entirely out of the existing holders — mostly founders — rather than being shared with the new investor. It quietly shifts roughly 5–8 points of ownership onto founders at a priced round. Negotiating the pool as a post-money line item, or sizing it to only the next 18 months of hiring, protects the founders’ stake.
- Is the result binding, and is this financial advice?
- No. This is a starting point for the conversation, not legal, tax, or financial advice. Whatever you agree on should be documented, put on a vesting schedule, and papered by a qualified lawyer. Founder cash is best structured as a SAFE or loan to be repaid, rather than as equity that permanently skews the split.
Sources & principles
- Carta, Founder Ownership Report 2026
- Michael Seibel / Y Combinator — splitting equity
- Paul Graham — The Equity Equation
- Cooley GO — founder stock & vesting
This tool is for guidance only and is not legal, tax, or financial advice. Ownership projections track medians for a typical company; your rounds, pool sizes, and terms will differ. Document any agreement and have it reviewed by a qualified professional.