Founder Equity Split Calculator

Splitting founder equity is the most important contract you'll sign with your co-founder, and the easiest one to under-think. The default — "50/50, we're friends" — frequently survives until the company starts working, then unravels. A weighted-contribution split forces a conversation about what each founder actually brings.

This calculator scores founders across six dimensions and produces an illustrative split. It is not a recommendation — it's a structured way to have the conversation.

The six dimensions

• Idea — who saw it first, who framed it. Worth weighting, but rarely the largest factor in long-term outcomes.
• Commitment — full-time vs. part-time, opportunity cost. The single highest-signal dimension in our default weighting.
• Work — direct output: code shipped, customers acquired, ops run. Equal-weighted with commitment.
• Expertise — domain depth that materially de-risks the company.
• Network — relationships that open doors (hires, customers, capital). Useful but quickly amortized.
• Capital — sweat-cash contribution at founding. Common in family/friends configurations.

The default dimension weights bias toward commitment (30%) and work (30%), with idea (10%), expertise (15%), network (10%), and capital (5%) trailing. NVCA — founder vesting guidance — nvca Foundrs.com — other

Vesting

Whatever split you arrive at, vest it. The standard is 4-year vesting with a 12-month cliff — meaning a founder who leaves in the first 12 months keeps zero shares. This protects every founder from being diluted by a co-founder who walks. Cooley GO — founder vesting — cooley-go

Investors will insist on this at the priced round. Doing it on day one is cheaper than retrofitting it after a falling-out.

What this calculator does not do

• Adjust for vesting (the share number reflects the target, not what's vested at any point).
• Account for future hires — co-founders added later usually go through the option pool, not the cap table.
• Suggest a fair answer. There is no fair answer. There is only the answer you can all sign.

Take this to your attorney

• Bring the proposed split. Bring the dimension weights and the inputs.
• Ask about vesting structure — 4-year / 1-year cliff is standard, but cliff length is negotiable.
• Ask what happens to unvested shares if a founder leaves "for cause" vs. without cause.
• Ask about acceleration on change of control (single-trigger vs. double-trigger).
• For Georgian-incorporated companies considering a Delaware flip later: ask how the founder vesting carries over.