Founder equity tool

Co-Founder Equity Split Calculator

A co-founder equity split calculator estimates a fair startup ownership split from each founder's role, idea contribution, capital, time, execution responsibility, and risk. Use it to make the first equity conversation more concrete before creating legal documents.

Founder pool

85%

Option pool

15%

Founder score

Score the founders

Use 0 for no contribution and 5 for a major contribution.

Role criticality5/5How central this person is to product, sales, operations, or fundraising.Original idea5/5Who brought the initial insight, customer access, or market thesis.Capital contributed2/5Cash, unpaid infrastructure, guarantees, or other real financial input.Time commitment5/5Full-time commitment, nights-and-weekends risk, or availability to execute.Execution ownership5/5Who is accountable for building, selling, recruiting, and shipping.Opportunity cost4/5Salary forgone, career risk, reputation risk, or personal guarantees.

Role criticality4/5How central this person is to product, sales, operations, or fundraising.Original idea2/5Who brought the initial insight, customer access, or market thesis.Capital contributed5/5Cash, unpaid infrastructure, guarantees, or other real financial input.Time commitment4/5Full-time commitment, nights-and-weekends risk, or availability to execute.Execution ownership4/5Who is accountable for building, selling, recruiting, and shipping.Opportunity cost3/5Salary forgone, career risk, reputation risk, or personal guarantees.

Role criticality3/5How central this person is to product, sales, operations, or fundraising.Original idea1/5Who brought the initial insight, customer access, or market thesis.Capital contributed1/5Cash, unpaid infrastructure, guarantees, or other real financial input.Time commitment3/5Full-time commitment, nights-and-weekends risk, or availability to execute.Execution ownership3/5Who is accountable for building, selling, recruiting, and shipping.Opportunity cost2/5Salary forgone, career risk, reputation risk, or personal guarantees.

Employee option poolReserve equity for future hires before splitting the founder pool.15%

How to use this calculator

Score each founder

Rate each founder from 0 to 5 across role, idea, capital, time, execution, and risk.

Reserve the option pool

Set aside equity for future hires before dividing the remaining founder pool.

Review the split and vesting

Use the weighted ownership table and vesting notes as a starting point for a founder discussion.

Founder equity FAQ

What is a co-founder equity split calculator?

A co-founder equity split calculator estimates how much ownership each founder should receive based on role, idea contribution, capital, time commitment, execution ownership, and risk.

Should co-founders always split equity equally?

Equal splits are simple, but they are not always fair. If founders have very different commitments, risk, cash contributions, or execution responsibilities, a weighted split can make expectations clearer.

How large should the employee option pool be?

Many early startups reserve 10% to 20% for an employee option pool. The right amount depends on hiring needs, funding plans, and how much equity must remain available for future team members.

Do founders need vesting?

Yes. Founder vesting protects the company if someone leaves early. A common setup is four-year vesting with a one-year cliff, but every founder agreement should be reviewed with counsel.

Is this calculator legal advice?

No. This tool is a planning aid for discussion. Use it to create a starting point, then work with an attorney to document the final founder agreement, vesting terms, and equity grants.

Next step

Validate the business behind the split

Equity only matters if the startup becomes valuable. Idea Score helps founders evaluate demand, market size, competition, risks, and next experiments before spending months on the wrong idea.

Score an idea