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Co-Founder Equity Split Calculator
Score each founder on five factors, choose how much each factor matters, and get a suggested split to discuss with your co-founders.
Founders and scores
For each factor, set how much it matters (weight, 0 to 10) and score each founder from 0 to 10.
Suggested split
Suggested equity split
56.3% / 43.7%
Treat this as the start of the conversation, not the final answer. Agree the scores together, then put vesting on every founder's shares.
- Founder A (129 points)
- 56.3%
- Founder B (100 points)
- 43.7%
- Total points
- 229
How to use the co-founder equity split calculator
- Choose the number of founders (two to four) and type their names.
- Set a weight from 0 to 10 for each factor. The weight says how much that factor matters for your business. A weight of 0 removes the factor.
- Score each founder from 0 to 10 on each factor. Score what is true today and what each person has committed to, not what they might do one day.
- Read the suggested split. It updates as you type, with each founder's points next to their share.
It works best when each founder fills it in alone first, then you compare. The factors where your scores disagree are the ones you need to talk about before you sign anything.
| Factor | What to score |
|---|---|
| Idea and early work | Who came up with the idea, and what each person has already built, tested or sold |
| Time commitment from now on | 10 for full time with no other job, about 5 for half time |
| Skills the business needs | Experience, industry contacts and skills that would be hard to hire for |
| Cash put in | Money invested in the company that is not being repaid as a loan |
| Responsibility and risk | Who leads the company, and who gives up the most salary or security |
The equity split formula
Formula
Founder points = sum of (factor weight x founder score) for every factor. Founder share = founder points / total points of all founders.
This is a weighted scoring model, one of several conventions for dividing founder equity. The other common ones are an equal split, and a dynamic split where shares are earned over time as each person contributes. The calculator starts with weights of 2 for the idea, 5 for time, 4 for skills, 3 for cash and 3 for responsibility and risk. Those starting weights are an example, not a rule, so change them to fit your business.
A worked example with two founders
Say Founder A had the idea and is going full time as CEO. Founder B is the stronger technical expert but is keeping a job for now and working half time. Both put in the same amount of cash. Using the starting weights:
| Factor | Weight | Founder A score | Founder B score | A points | B points |
|---|---|---|---|---|---|
| Idea and early work | 2 | 8 | 3 | 16 | 6 |
| Time commitment from now on | 5 | 10 | 5 | 50 | 25 |
| Skills the business needs | 4 | 6 | 9 | 24 | 36 |
| Cash put in | 3 | 5 | 5 | 15 | 15 |
| Responsibility and risk | 3 | 8 | 6 | 24 | 18 |
| Total | 129 | 100 |
Total points are 229. Founder A gets 129 / 229 = 56.3% and Founder B gets 100 / 229 = 43.7%. If Founder B commits to full time and scores 10 on time, B rises to 125 points and the split becomes 50.8% to 49.2%, and the calculator's note tells you a gap that small is within the margin of guessing.
How to turn the result into an agreement
- Weight the future over the past. The idea is the start. Most of the value is created by the years of work after it, so time and skills usually deserve more weight than who thought of it first.
- Round to numbers you can both defend. The calculator gives one decimal place, but nobody can measure a contribution that precisely. Treat the output as a range and agree a round figure.
- Add [vesting](/resources/glossary/vesting). Vesting means each founder earns their shares over time, so someone who leaves early does not keep the full stake. See how it plays out with the vesting schedule calculator.
- Decide who breaks a tie. An exact equal split between two founders needs a written way to settle disagreements.
- Write it down and get it checked. Put the split, the vesting terms and each person's role in a founders' agreement. Company and tax rules differ by country and state, so ask a startup lawyer before you issue shares.
- Look ahead to investors. Your split is the top of your cap table. Use the equity dilution calculator to see what each founder would hold after a funding round.
If you are still looking for the right person, read how to find a co-founder first. And if you are building alone for now, Fonda gives you an AI co-founder called Marty that guides you from idea to launch, including a Legal and setup step. It is free to start.
What the calculator leaves out
- Vesting, cliffs and what happens when someone leaves. The split is only the starting allocation.
- An option pool and investors. The result divides 100% between founders. Shares for employees, advisors and investors come later and dilute everyone.
- Salary differences. If one founder is paid and another is not, you may want to settle that in pay or in the risk score.
- Loans and intellectual property. Money lent to the company and patents or code brought in from outside are usually handled in separate agreements.
- Judgment. The scores are your opinions turned into numbers. The calculator makes the trade-offs visible. It cannot tell you whether the scores are honest.
Frequently asked questions
Should co-founders split equity 50/50?
An equal split is reasonable when you start at the same time, commit the same hours and take similar risk. It is harder to justify when one founder is part time or joins after much of the early work is done. Score the factors separately first. If the result lands near equal, an equal split is easy to defend.
How much equity should the person with the idea get?
Usually less than they expect. An idea counts, but a business is built by testing it with customers, building the product and selling it. That is why this calculator starts the idea factor at a lower weight than time and skills. Raise it if the idea comes with something concrete, such as a working prototype or signed customers.
What if a co-founder joins later?
Score them the same way, but be honest about the early work score, since the existing founders have already taken the idea some distance. Many teams also give a later co-founder a fresh vesting schedule that starts on the day they join.
Can we change the equity split later?
You can, but it is harder than getting it right at the start. Changing a split after shares are issued needs everyone's agreement, and it may have tax consequences that depend on where you live. Vesting is the usual way to build in fairness over time without renegotiating.
Is this calculator free?
Yes. It runs in your browser, needs no signup and does not store your names or scores.
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