Why not just split equity equally?

Equal splits are quick and signal trust, but they assume equal contribution forever. When one founder goes full time and another stays part time, or one puts in savings, an equal split quietly becomes unfair. A dynamic split records what each person actually risked and adjusts as that changes.

Is the idea worth equity?

In this model, no. An idea becomes valuable through the work and money that follow it, and those are already counted. If the idea came with real assets, such as a prototype, customers, or filed IP, enter them as assets at fair value.

When should the split stop moving?

Most teams freeze the split when outside money arrives or the company can pay market salaries, because from then on nobody is betting unpaid work. Until then, revisit the numbers each quarter so the agreed shares track reality.

BUSINESS

Startup Equity Split Calculator

Split startup equity between co-founders fairly. Value unpaid time, cash, and assets as slices of a growing pie, and see how the split shifts month by month.

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How the equity split is calculated

For each founder, value a month of their work at the market rate for the role: hours per week × hourly rate × 52 ÷ 12. Subtract any cash salary the company pays. What is left is unpaid time, the founder’s bet on the company.
Turn each bet into slices. Unpaid time and assets brought in (equipment, prior work, IP) earn the time multiplier, 2 by default. Cash invested or expenses covered earns the cash multiplier, 4 by default, because cash is scarcer and would otherwise be borrowed.
Add up every founder’s slices as of the month you choose. A founder’s share is their slices divided by everyone’s slices, so the pie grows while people keep contributing and shrinks for no one.
Project the same arithmetic month by month to the horizon, and compute the long-run split: the ratio of each founder’s monthly unpaid time, which is where the shares settle if everyone keeps their current pace.

Worked example

Alex works full time at a $75 market rate with $2,000 in; Sam works 15 hours a week at $90 with $25,000 in and a $5,000 prototype. On day one Sam holds about 93% because only the cash and prototype count. By month 12 Alex has 56%, by month 24 about 62%, and the long-run split is 69/31. The founders can see that drift before signing anything.

Assumptions and boundaries

Contributions are steady: the same hours and pay every month from the month a founder joins. Change the inputs to model a new arrangement.
Cash and assets count in full from the month a founder joins. Time counts for each completed month after that.
Market rates are what the company would pay a competent stranger for the work, not what a founder earned at a previous job.
The multipliers are the Slicing Pie defaults. Teams may agree on different ones; the point is to agree before the work is done.

Important limitation: This is a fairness model, not a cap table or a legal agreement. It ignores vesting, option pools, investor dilution, taxes, and what happens when a founder leaves. Dynamic splits usually freeze at a funding round or incorporation; record the agreed split in your founders’ agreement with a lawyer.

Sources and review

Methodology and links reviewed October 15, 2026. This educational estimate is not financial, tax, legal, investment, or lending advice.

Frequently asked questions

Why not just split equity equally?: Equal splits are quick and signal trust, but they assume equal contribution forever. When one founder goes full time and another stays part time, or one puts in savings, an equal split quietly becomes unfair. A dynamic split records what each person actually risked and adjusts as that changes.
Is the idea worth equity?: In this model, no. An idea becomes valuable through the work and money that follow it, and those are already counted. If the idea came with real assets, such as a prototype, customers, or filed IP, enter them as assets at fair value.
When should the split stop moving?: Most teams freeze the split when outside money arrives or the company can pay market salaries, because from then on nobody is betting unpaid work. Until then, revisit the numbers each quarter so the agreed shares track reality.