Co-founder Equity Split Calculator
Enter what each co-founder brings and how much time they commit from now on. The calculator shows two splits side by side: a weighted factor model and a Slicing Pie view of contributions so far. Then it shows each founder's vesting and their stake after a seed round. Everything runs in your browser. We do not store your inputs.
Your founding team
What to enter
- A builder makes the product. A distributor sells it and brings in customers.
- Salary forgone: market pay for the work this founder does, minus what the company pays. Use the part-time figure for part-time work.
- Cash invested: money the founder put in and does not expect back as a loan.
- Code, designs or IP: what it would cost to buy or rebuild today. An idea alone counts as 0.
- Customers or audience: "A few" means early users or a small audience. "Many" means paying customers or a large audience that fits the product.
Factor weights
Each factor splits the company by its own measure. The weights set how much each factor counts. The defaults put 60 on role and commitment from now on, and 40 on what founders have put in so far. Change them to match what your team values.
Total weight: 100. The model scales the weights to 100. A factor shows "Not used" when no founder has a value for it. Its weight then goes to the other factors.
Suggested split
55.0% / 45.0%
Factor model
- Founder A55.0%
- Founder B45.0%
Slicing Pie
- Founder A78.9%
- Founder B21.1%
Slicing Pie counts only what each founder has put in so far. Unpaid salary and IP count at 2x their value. Cash counts at 4x.
Split to use for vesting and the seed view
Vesting schedule
Each founder vests over 4 years. With a 1-year cliff, nothing vests in the first 12 months. At month 12, 25% vests at once. The rest vests monthly.
| Founder | Stake | Today | Year 1 | Year 2 | Year 3 | Year 4 |
|---|---|---|---|---|---|---|
| AFounder A | 55.0% | 0.0% | 13.8% | 27.5% | 41.3% | 55.0% |
| BFounder B | 45.0% | 0.0% | 11.2% | 22.5% | 33.7% | 45.0% |
Each cell shows the share of the whole company the founder owns outright at that point. Unvested shares go back to the company when a founder leaves.
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Email me this split
Get the split, the vesting table and a founders' agreement checklist in your inbox. The email goes to your own address only, and it labels the founders A to D.
A builder looking for a distributor, or the other way round?
Founder Ventures works with builders and distributors on bootstrapped B2B software. You get shared infrastructure and a network of founders who build the same way. We start from markets with proven demand.
Apply to Founder VenturesTypical co-founder equity splits
Equal splits are now common for two-founder teams. In Carta's data, 45.9% of two-founder teams split equity equally in 2024. In 2015 the figure was 31.5%.
Larger teams split equally less often. In 2024, 26.9% of three-founder teams chose an equal split. Carta's Founder Ownership Report puts the median two-founder split at 55% and 45%.
Equal splits made fast can cost a team. Thomas Hellmann and Noam Wasserman studied 1,476 founders in 511 ventures. Teams that agreed an equal split quickly raised their first round at lower pre-money valuations. The authors trace the gap to differences between the teams. They do not find that the equal split itself causes it.
Technical co-founder equity
A technical co-founder who joins at the start and works full time usually gets an equal or close to equal share. Michael Seibel of Y Combinator argues for equal splits. A company of real value takes 7 to 10 years to build, so a head start of a few months matters little.
This calculator calls the technical co-founder the builder. It gives the builder and the distributor the same role score. A B2B software company needs a product and a way to sell it, and each role is hard to replace.
The split moves when a co-founder joins after the product exists, works part time, or keeps a salary. Enter those facts in the calculator. The work done, salary forgone and IP factors then show the difference.
How the calculator works
The factor model scores each founder on six factors. On each factor, a founder's share is their score divided by the team's total score. The weights then blend the six shares into one split.
Factor model
Founder share = sum over factors of (weight / total weight) × (founder score / team score)
Builders and distributors score 1 on core role. Any other role scores 0.5. Full time scores 1 and part time scores 0.5. Work done so far is months worked, halved for part-time work. Cash and IP count in dollars. Customers or audience score 0 for none, 1 for a few and 3 for many.
A factor drops out when no founder has a value for it. Its weight goes to the other factors. If no factor separates the founders, the split is equal.
The Slicing Pie view follows Mike Moyer's model. Each founder earns slices for what they have put at risk. Unpaid salary and IP earn 2 slices per dollar. Cash earns 4 slices per dollar, because cash is harder to find. A founder's share is their slices divided by all slices.
The seed view takes the round and the new option pool out of the founders' stake. Each founder keeps the same share of the founding team. The defaults are Carta medians: 19.5% sold in a priced seed round and a 12.1% employee pool.
Limits
No formula knows your team. The factor weights are our defaults, and the Slicing Pie view counts only the past. Use both views to start the conversation, then agree the split in writing. This calculator is not legal or tax advice.
Vesting, cliffs and leavers
Vesting protects the founders who stay. Each founder earns their shares over time. When a founder leaves early, the company buys back the unvested shares.
Four years is the norm. Carta reports that most founders vest over 4 years, like employees. Many founders skip the 1-year cliff, and some teams credit the months already worked. The calculator lets you test both choices.
Investors often ask founders to re-vest at a priced round. Carta notes that the new schedule usually runs for another 4 years.
US founders who buy shares that vest usually file an 83(b) election. The IRS deadline is 30 days after the shares transfer. You can file on Form 15620.
Frequently Asked Questions
How should co-founders split equity?
Start from what each founder will do over the next 4 years. Then adjust for what each founder has already put in: work, unpaid salary, cash, code and customers. The calculator runs a weighted factor model and a Slicing Pie view on the same inputs. Put every founder on a 4-year vesting schedule, whatever split you choose.
What is a typical co-founder equity split?
For two founders, an equal split is the most common single outcome. Carta found that 45.9% of two-founder teams split equally in 2024. Its Founder Ownership Report puts the median two-founder split at 55% and 45%. Three-founder teams split equally less often, at 26.9% in 2024.
How much equity should a technical co-founder get?
A technical co-founder who starts at the same time and works full time usually gets an equal or close to equal share. The calculator gives builders and distributors the same role score. The share drops when the technical co-founder joins late, works part time or keeps a market salary.
What does Y Combinator say about co-founder equity splits?
Michael Seibel of Y Combinator argues for equal splits. He points out that a valuable company takes 7 to 10 years to build. Small differences in the first year should not decide the split for the next nine. He also advises vesting, so a founder who leaves early does not keep the full stake.
What is a 4-year vesting schedule with a 1-year cliff?
Each founder earns their shares over 48 months. With the cliff, nothing vests in the first 12 months. At month 12, a quarter vests at once. The rest vests monthly until month 48. A founder who leaves before the cliff keeps no shares.
What is Slicing Pie?
Slicing Pie is a dynamic equity model by Mike Moyer. Each founder earns slices for unpaid work, cash and other contributions at market value. Non-cash contributions count 2x and cash counts 4x. It suits teams that work unpaid for an uncertain period. It counts only the past, so it gives no credit for commitment from now on.
Should a part-time co-founder get less equity?
Usually, yes. Carta links most unequal splits to differences in commitment. In this calculator, part time scores half of full time on commitment and on work done. If the part-time founder plans to go full time, agree the date and the new terms in writing.
Do co-founders need to file an 83(b) election?
US founders who buy shares that vest usually file one. The election must reach the IRS within 30 days of the share transfer, and the IRS accepts no late elections. You can use Form 15620. Ask a tax adviser about your own case.
This calculator is not legal or tax advice. Talk to a startup lawyer before you sign a founders' agreement.
Sources
- Carta, A shift is underway in how startup co-founders split their equity (2024)
- Carta, Founder Ownership Report
- Carta, Founder Ownership Report 2026
- Carta, Less than 10 percent of seed rounds sell 30 percent or more
- Carta, How long should founder vesting schedules be?
- Michael Seibel, How to Split Equity Among Co-Founders (Y Combinator)
- Hellmann and Wasserman, The First Deal: The Division of Founder Equity in New Ventures (NBER)
- Mike Moyer, The Slicing Pie model
- Slicing Pie, Allocation framework and multipliers
- IRS, Form 15620: Section 83(b) Election