Co-Founder Equity Split Calculator

Two ways to arrive at a split

Weigh contributions is the factor method, the approach behind Frank Demmler's Founders' Pie Calculator and most tools like it. The founders agree on what matters to this particular business (full-time commitment, cash, salary given up, the idea and any code or designs, expertise, the job each will do, the customers and contacts each brings), give each factor a weight, and then score each founder against it. It suits a team deciding once, at the start, before much has been contributed.

Track contributions is the dynamic method in the spirit of Mike Moyer's Slicing Pie. Nothing is fixed in advance. Each founder's unpaid time is valued at what the market would pay for that work, less any pay actually taken (the Pie Slicer guide calls this the "fair market salary less whatever cash compensation is being paid"), and every contribution is converted into slices. Moyer recommends "a non-cash multiplier of two (2) and a cash multiplier of four (4)", on the reasoning that it is much harder to save a dollar than to earn one. Each founder's share is their slices over the total, so the split keeps moving until the company can pay its people, at which point the pie is frozen and becomes the cap table.

How the arithmetic works

In the weighing method, each factor's weight is shared out among the founders in proportion to their scores, and the shares are added up. Say time carries a weight of 3 and both founders work full time, scoring 10 each: each takes 1.5 points. Cash carries a weight of 2, and one founder put in three times as much as the other, scored 6 and 2: the first takes 1.5 points, the second 0.5. With only those two factors the first founder has 3 points of 5, or 60%, and the second 40%. A factor nobody scores on drops out, so adding a factor that does not apply to this business changes nothing.

In the tracking method the sums are plainer. A founder who works 1,000 unpaid hours at a market rate of $75 an hour has contributed $75,000 of time, which at the 2x multiplier is 150,000 slices. A founder who puts in $40,000 of cash has, at 4x, 160,000 slices. Expenses paid out of pocket count as cash; equipment and intellectual property count at their fair value, as non-cash. The multipliers are editable because they are a convention, not a law of nature.

The option pool comes off the top. A pool of 10% leaves the founders 90% between them, in the proportions above. Set it to 0 for a business that will never hire with equity, which is most small businesses that are not raising venture money.

Vesting, and why it matters more than the percentages

A split decides who owns what if everyone stays. Vesting decides what happens if someone does not. Under a typical schedule, as Cooley GO describes it, founder stock vests in monthly or quarterly instalments over four years, often with a one-year cliff. With four years, a one-year cliff and monthly vesting, nothing vests for twelve months, a quarter vests at the cliff, and 1/48 of the grant (2.08%) vests each month after. A founder who leaves at month 18 keeps 37.5% of their grant and the company can buy back the rest, usually at what was paid for it. The chart in the calculator draws the schedule for whichever founder is chosen.

Founders of a corporation who receive stock subject to vesting have one deadline that cannot be fixed later: an election under section 83(b) of the tax code must be filed "not later than 30 days after the date the property was transferred" (26 CFR 1.83-2(b)). The IRS now has a form for it, Form 15620. Miss it, and each tranche that vests can be taxed as income at its value on the day it vests. How to file an 83(b) election goes through the filing, and founder vesting schedules and cliffs covers acceleration and the LLC equivalent.

What the data says about how founders actually split

Founding team	Split equally	Source
Two founders, 2015	31.5%	Carta, Founder Ownership Report (data to 2024)
Two founders, 2024	45.9%
Three founders, 2015	12.1%
Three founders, 2024	26.9%

Over 2015 to 2024 as a whole, Carta found two-founder teams split equally 38.8% of the time, and the median two-founder split was 55% and 45%; in 2024 alone the gap had nearly closed, to 51 and 49. Even splits get rarer as teams grow: 16.1% for three founders over the decade, and for four or five Carta calls them "exceedingly rare". The figures describe venture-tracked startups on Carta's platform, which skews toward companies that raise money; a two-owner services firm or shop is not in the sample.

What the calculator cannot tell you

Any formula reflects the weights someone chose, and the scoring is a negotiation in disguise. Its use is to make the disagreement specific: two founders who both expected 60% can see which factor they valued differently, and talk about that instead. The strongest objection to any method is that the founder who will matter most in year three may not be the one who contributed most in month one. That is true, and it is the argument for vesting and for revisiting the split at a defined event (a first hire, a first raise), not for skipping the arithmetic.

It also does not set the legal terms. A split is real only once it is in a stock purchase or operating agreement, with vesting and a buyback right, and in a partnership with no agreement the default may surprise everyone: under the Uniform Partnership Act (1997) §401(b), partners share profits equally regardless of what each put in. Splitting equity between co-founders covers the conversation, the sweat equity case what changes when one partner brings the money and the other the work, and splitting profits the separate question of who gets paid what each year. When the time comes to put it in writing, the partnership agreement checklist lists the clauses.

General information, not legal or tax advice. Equity, vesting and 83(b) elections have tax and securities consequences that depend on the entity and the state; a lawyer and an accountant should see the actual documents before anyone signs.