How to split equity between co-founders fairly

To split equity between co-founders is to make the first deal of the company: who owns what share, and why. Most teams decide it too fast and talk about it too little. This guide shows what should count, why 50/50 is often a reflex rather than a result, and how vesting keeps the deal fair when life changes.

Why does the way you split equity matter so much?

An equity split is the share of the company each founder holds, and with it the share of every future gain, vote and dilution. It shapes who feels like an owner and who feels like a helper. A split that one founder quietly resents will surface later, usually at the worst moment: a financing round, a hard quarter, or a co-founder thinking about leaving.

Teams tend to settle this early and quickly. In a study of more than 3,700 founders, Thomas Hellmann and Noam Wasserman found that 73 percent of teams split their equity within the first month, many of them in a single conversation. Teams that split quickly were far more likely to choose an equal split, and those quick equal splits were later the ones most often regretted.

The lesson is not to wait for months. It is to have one honest conversation early, with a method behind it, instead of a handshake over a 50/50 nobody questioned.

What should count when you split equity between co-founders?

Equity rewards contribution and risk. A fair split starts with a list of what each person brings now and commits to bring over the next years. The usual factors:

• Time. Full-time from day one weighs far more than evenings and weekends. Someone who keeps a salary elsewhere carries less risk.
• Money. Cash a founder puts in, or salary a founder gives up, is a real contribution. Treat it as such, but do not let it dominate the split: a loan or a small priced round can price money separately.
• The idea. It is worth something, but less than most people think. Execution over years is what builds the company.
• Skills and experience. A rare skill the company cannot buy, a prior exit, or a network that opens the first customers all count.
• Role and responsibility. The person who carries the company as CEO, or who builds the product alone for a year, takes on more.

Several founders have published frameworks for this. Justin Kan's guide at the Long-Term Stock Exchange starts every founder at a base and adds or subtracts for the factors above. Others score each factor from one to five, weight them, and normalise the totals to 100 percent. The method matters less than the conversation it forces: you have to say out loud what you expect from each other.

How do you split equity when the contributions differ?

Score first, talk second. Each founder fills in the factors alone, then you compare. Big gaps in the scores are the real agenda: they show where expectations differ, and that is what you need to resolve before any number is final.

A worked example. Two founders start a software company. One leaves a job and works full-time from day one, brings the industry contacts and will sell. The other keeps a part-time job for six months and builds the product. With time weighted highest, a split around 60/40 is common, often with a plan to move closer to equal once the second founder goes full-time. A third founder who joins six months later, after the first customers, usually gets less than the two who took the early risk.

If the split comes out equal after honest scoring, 50/50 is the right answer. If it comes out at 55/45, and the smaller share feels wrong, say so now. A split that one side accepts only to avoid a fight is not a deal, it is a delay.

Avoid two extremes. One is the dynamic split that recalculates shares every month from logged hours. It sounds fair but turns founders into bookkeepers of each other. The other is giving the idea a large premium: an idea without execution is worth very little, and the premium becomes a grievance once the work starts.

Why does vesting make every split safer?

Vesting means a founder earns the shares over time instead of holding them all from day one. The standard, which investors expect and most lawyers recommend, is four years with a one-year cliff: nothing vests in the first year, a quarter vests at the first anniversary, and the rest vests monthly after that.

Vesting changes the question from "what if we got the split wrong" to "what if someone leaves". A founder who leaves after eight months keeps nothing. A founder who leaves after two years keeps half of their shares, which is fair for two years of work, and the rest returns to the company. Without vesting, the leaver keeps everything. Investors call that dead equity, and many will not invest until it is cleaned up, which means buying the leaver out at a price nobody enjoys.

In a GmbH or a FlexCo in Germany and Austria, shares exist in full from the day the company is founded, so founder vesting is agreed by contract as reverse vesting: the founders agree that unvested shares can be bought back at nominal value if someone leaves. Law firms such as Kanzlei Herfurtner describe the clauses that make this hold, including good leaver and bad leaver rules and the price in each case. Have a lawyer draft these; a vesting clause that fails in court protects nobody.

When and how should you write it down?

Decide within the first weeks of working together, before the first customer, the first hire and the first investor conversation. The longer you wait, the more the split carries, and the harder the talk becomes.

Write it into a founder agreement, even before the company exists. The agreement should hold the split, the vesting schedule, what counts as a good or bad leaver, who decides what, how much time each founder commits, and what happens to the idea and the code if the team breaks up before incorporation. Once you incorporate, the same terms go into the shareholders' agreement, as firms like Compound describe for German start-ups. Our guide on the questions to ask a potential co-founder covers the conversation that should come before the contract.

Then model the numbers. Our free cap table calculator shows what the founders' split looks like after an option pool and two financing rounds, so everyone sees that a 60/40 split today becomes, for example, 42/28 after a seed round. Seeing the dilution together often takes the heat out of the last few percentage points.

What are the common mistakes?

• Splitting in the first conversation. The 73 percent who split within a month include many who never discussed contribution at all.
• Equal shares for unequal commitment. Half the company for a founder who stays part-time for a year is the most common source of resentment.
• No vesting because "we trust each other". Vesting is not about trust, it is about the cases nobody plans for: illness, a family move, a better offer.
• Pricing the idea too high. The idea gets a small premium at most.
• Treating the split as final. Roles change. Agree now on when you would revisit it, and tie changes to vesting rather than to new promises.

If you are still looking for the right person to have this conversation with, see how Cofoundista works and the open co-founder roles: the fit score covers equity expectations on both sides, so the first talk about shares starts from the same page.