Co-founder Equity Split Calculator

Each factor has an importance weight from 0 to 10, set for your company. Each founder gets a score from 0 to 10 on every factor. Multiply, add up, and each founder's share of the points is their share of the founder equity.

The defaults weight full-time commitment and building the product highest, and the original idea lowest. That reflects where startup value comes from: years of execution, not the first conversation. Change any weight; the split updates live and the link captures your exact inputs.

The calculator opens with two founders: Asha, who brings the idea, early capital, domain knowledge and the sales network, and Ben, who builds the product. Both are full time. With the default weights and a 10% option pool:

Score → points for each factor. The split is close to equal because the two founders bring different but comparable things, which is the usual case for a healthy founding team.

Equal splits get a bad reputation, but they are often the right answer for a team that starts together, works full time and needs each other's skills. A slightly unequal split that both people resent costs more than a few percentage points of fairness.

Split unequally when the contributions are clearly unequal: one founder is part time, someone joined months later, one person is putting in significant cash, or one founder is giving up a far larger salary. If the calculator shows a gap of more than a few percent, talk about the factors driving it rather than the number.

Vesting turns equity from a gift into something earned over time. With the common 4-year schedule and 1-year cliff, nothing vests for the first twelve months, 25% vests on the first anniversary, and the rest vests monthly over the next three years.

It protects the founders who stay. Without it, a co-founder who leaves after three months keeps their full slice, and investors will usually insist on fixing that before they put money in. Agree on vesting at the same time as the split, and write both into a founders' agreement.

A fixed split is a forecast of who will contribute what. Dynamic equity models avoid forecasting by tracking contributions as they happen. The best known is Slicing Pie by Mike Moyer, which values unpaid time and cash at market rates, applies a risk multiplier, and gives each person a share proportional to their accumulated contributions.

It suits teams that start part time or bootstrap for a long time. The trade-off is bookkeeping: someone has to record every contribution, and the model usually freezes into a fixed split when the company raises money or starts paying salaries.

• Splitting before deciding roles. Agree who is CEO, who builds and who sells first. The scores only make sense once roles are clear.
• Paying for the idea. Over-weighting the original idea is the most common way first-time founders end up with a split that feels wrong a year later.
• No vesting. The split matters far less than what happens when someone leaves.
• Mixing cash and sweat. Large cash contributions are often cleaner as a loan or SAFE than as extra founder equity.
• Never revisiting. If one founder goes part time, update the agreement instead of quietly resenting it.