How to Split Equity Between Co-Founders, and Agree the Rest

Why does the co-founder equity conversation matter so much?

Most founding teams avoid the equity conversation for as long as they can, because it feels like ranking each other. The cost of waiting is that everyone forms a private number, and the gap between those numbers grows with every month of work.

The people side of a startup is not a soft topic. In a talk recorded by Stanford's eCorner, Noam Wasserman said that people problems, including tensions between founders as a company gets going, accounted for 65% of failures among the high-potential startups in the venture capital data he cited. CB Insights' March 2026 analysis of 431 venture-backed shutdowns found 70% ran out of capital, but noted that running out of money is usually the final cause rather than the root problem. Underneath many of those root problems are founder decisions, and how well founders make them together.

Most teams do stay together. Carta's Founder Ownership Report (January 2025) found fewer than 25% of two-founder teams split within four years. But the share splitting in their first year rose from 4% in 2015 to 7.5% in 2024, so planning for a departure is sensible, not pessimistic.

What are the main ways to split founder equity?

There are four broad approaches. None is right for everyone, and many teams compare two or three before deciding.

A dynamic split, popularised by Mike Moyer as Slicing Pie, lets each founder's share move in proportion to the at-risk contributions they make: unpaid time valued at market rates minus any pay, cash, and agreed values for things like IP or customer relationships. The split keeps moving until you freeze it, typically at incorporation or a first funding round.

It can feel fairer when commitments are uncertain and nobody is paid. Its weaknesses are the bookkeeping, the need to agree values, and the fact that it rewards what has already been put in. A founder who joined last month but will do much of the next four years' work can look small. If you use it, agree the freeze date in advance and have a lawyer document the result.

Should co-founders split equity equally?

Equal splits are simple, signal that everyone is all in, and avoid a ranking conversation at a fragile moment. They are also becoming more common. Carta's January 2025 report, covering more than 45,000 startups incorporated on its platform between 2015 and 2024, found that two-founder teams split equally 31.5% of the time in 2015 and 45.9% in 2024; three-founder teams went from 12.1% to 26.9%. The median two-founder split in 2024 was almost exactly 51 to 49.

An equal split is a good choice when time commitments and roles over the next two years are genuinely similar. It is a poor choice when one founder is full-time and another part-time, or when one is about to put in years of work the other will not. In those cases, compare it side by side with a weighted split before deciding. Either way, add vesting.

How does a contribution-weighted split work?

A weighted split makes differences explicit and gives you something concrete to discuss. The key is to weight the future more than the past: the idea and the first few months matter, but the four years of work still to come matter far more.

• Agree six to eight factors together, such as time commitment over the next two years, how critical each role is to the next milestones, domain expertise and network, work done so far, IP brought in, salary forgone, cash and customers secured
• Weight each factor from 1 to 5
• Each founder scores every founder from 0 to 10 alone, without discussion
• Compare scores and discuss the two biggest differences before looking at totals
• Convert points to shares, compare with an equal split, sleep on it, then agree and record the reasoning
• Consider treating cash as a founder loan rather than extra equity, on terms an accountant documents

How do you have the equity conversation without falling out?

Treat it as a short project, not a single meeting. Over three to six weeks, test fit first, then agree roles and time, then the split, then vesting and leavers. Each step makes the next one easier, because you are pricing a future you have already described.

Start with a compatibility conversation in which each founder answers the same questions alone: what outcome they want, how long they can go without a salary, how many hours they can give, and what would make them walk away. Compare the answers and turn each difference into an agreement. Then agree the method for the split before anyone names a number, so nobody is bargaining against an anchor.

Two habits help more than any formula. First, write down the reasoning next to every number, in words each founder could repeat to an investor. Second, sleep on it: decide at the meeting after the one where you compared the options. A split that still feels fair the next morning is far more likely to feel fair in two years.

What are vesting and a cliff, and do founders need them?

Vesting means founders earn their shares over time. If a founder leaves early, unvested shares go back to the company or are bought back at a nominal price, depending on how your lawyer documents it. A common starting point is four years with a one-year cliff: nothing vests in the first 12 months, the months served vest together at the cliff, and the rest vests monthly. A founder who leaves at month 18 keeps 18/48 of their shares.

Vesting should apply to every founder, including the CEO and the founder with the idea. It protects the founders who stay, and investors usually expect it. To recognise months already worked, agree a vesting start date or a few months of credit, using the same rule for everyone. How vesting is documented and taxed differs by country, and some countries have short tax filing windows after shares are issued, so ask your lawyer and accountant.

What happens when a co-founder leaves?

That depends on what you agreed, which is why you should agree it now. In general terms, a good leaver leaves for reasons like illness, family circumstances or an agreed departure, and keeps vested shares. A bad leaver is usually defined narrowly, for things like serious misconduct or breaching IP or confidentiality duties, and may have vested shares bought back at a low price. Broad bad-leaver definitions invite disputes and may not be enforceable where you are.

The most useful exercise is to walk through scenarios with real numbers: a founder leaves before the cliff, at month 20 for a job, after a serious illness, for poor performance, after a breach, and when the company is sold. Write down what you want to happen to shares, role, board seat and IP in each case.

What else should a founders' agreement cover?

Equity and vesting get the attention, but most day-to-day friction comes from the other topics. Cover them in the same conversation and in the same written record.

• Treat the agreement first as a plain-words discussion record signed off as accurate, not as a contract
• Then brief a lawyer and an accountant together, with the record and your open questions
• Use AI tools to turn meeting notes into drafts and to list open questions; have founders decide and a qualified lawyer review anything legal

When should you incorporate, and what comes first?

Incorporate once the founders have agreed the basics above and the company needs to exist: to sign customers, open a bank account, take investment or hire. Most startups planning to raise form a company limited by shares where the founders, team and customers are. Delaware or Singapore holding structures can make sense for specific investor or market reasons and add cost and complexity, so decide with a lawyer rather than a blog post.

Registrar rules are changing too. In the UK, for example, identity verification for directors became a legal requirement on 18 November 2025, according to GOV.UK, and new directors provide a personal code when a company is incorporated. Check the current rules on your own registrar's site.

If you want the whole job in one place, The Founder Agreement and Company Set-Up Prep Kit from Bodhih Training includes a six-week plan, an alignment workbook, an equity split and vesting simulator, the discussion forms, a plain-words discussion record and a briefing pack for your lawyer and accountant.