Startup Equity Split Calculator

Determine fair equity splits for co-founders based on contributions including idea origination, time commitment, capital invested, domain expertise, leadership role, network, and prior startup experience.

Number of Co-Founders

How the Startup Equity Split Calculator Works

A startup equity split calculator is a tool that helps co-founders divide company ownership based on measurable contributions rather than guesswork. This calculator uses a weighted point system across seven factors: idea origination (1-5 points), time commitment (full-time 10, part-time 5, advisor 2), capital invested (0-10 points), domain expertise (0-5 points), CEO or leadership role (0-3 points), business connections (0-3 points), and prior startup experience (0-3 points). Each co-founder's equity percentage equals their total points divided by all co-founders' combined points, multiplied by 100. All calculations run privately in your browser with no data sent to any server.

Startup Equity Split for Different Scenarios

Equal splits (50/50) work when co-founders contribute equally across all dimensions, but research from Noam Wasserman's "The Founder's Dilemmas" shows that teams who split equity based on contributions outperform those who default to equal splits. A technical co-founder building the product full-time while the business co-founder works part-time should receive more equity. Similarly, a co-founder investing significant capital takes on financial risk that warrants additional ownership. Use this calculator to model different scenarios before finalizing your operating agreement. Consider vesting schedules (typically 4 years with a 1-year cliff) to protect all parties if someone leaves early.

Tips for Fair Startup Equity Negotiation

Have the equity conversation early, ideally before writing any code or incorporating. Use this calculator as a starting point for discussion, not the final answer. Consider future contributions alongside past ones since a co-founder who will lead fundraising for the next 5 years adds ongoing value. Document your agreement in a formal co-founder agreement reviewed by a startup attorney. Include vesting schedules, IP assignment clauses, and exit provisions. Revisit equity splits at major milestones such as funding rounds, pivots, or when roles change significantly. According to Y Combinator, the most successful startups tend to have near-equal splits among full-time co-founders, adjusted for meaningful differences in contribution.