How to Split Equity Fairly Between Cofounders

The equity split is among the earliest decisions a founder makes and one of the most damaging to get wrong. The damage usually traces back to the split itself: one that felt reasonable on the day, was never written down, and stopped matching reality once a founder’s contribution changed. Ownership feels permanent and personal, which is why it warrants a deliberate decision rather than a quick one.

The mistake most founders make

Two friends start a company, feel awkward about the conversation, and split it fifty-fifty within minutes to end the discomfort. There is no paperwork, no vesting, and no plan for what happens if one of them leaves.

Some months later one cofounder drifts, takes another job, or contributes far less, and leaves still owning half the company. The founder who remains then builds for years, raises money, and takes dilution, while half the ownership sits with someone no longer contributing. This is a common outcome, and it usually begins with a split chosen to avoid a conversation.

How to decide the split

A fair split reflects real contribution and future commitment. Work through it honestly:

• Who had the idea, and what is the idea worth against the years of building still ahead?
• Who has already done the work, and who is bringing mostly intentions?
• Who is taking the most risk: leaving a salary, putting in money, going full-time?
• Who will drive the most value from here? This matters most, because most of the company’s value is still ahead of it.

Sometimes the honest answer is a clean equal split, and that is appropriate when contributions really are equal. Reach that answer by actually having the conversation. A split you reason through and agree on tends to hold; one you fall into to avoid the conversation is the kind that breaks later.

Vesting is not optional

Whatever you decide, put every founder on vesting, so equity is earned over time rather than owned outright from day one. The standard is four years with a one-year cliff: nothing vests for the first twelve months, then a quarter vests at the cliff, and the remainder vests monthly (Carta explains vesting well).

This is what prevents the fifty-fifty outcome above. A cofounder who leaves after six months leaves with nothing, because they have not reached the cliff. One who leaves after two years keeps what they earned and no more. Vesting keeps ownership aligned with contribution over time, and it protects the founders who stay. Investors expect to see it before they fund a company, so you will need it in any case.

Team and advisors

Beyond the founders, set aside an option pool, commonly 10 to 20 percent of the company, to attract and reward early employees, all on the same four-year vesting. The pool dilutes the founders, so account for it early. It is one of the lines that appears plainly on your cap table.

Advisors are where founders most often overpay. A genuinely valuable advisor typically receives a fraction of a percent, rarely above one percent, and always with vesting so the equity is earned through actual contribution. Reserve generous grants for the few people who change the company’s trajectory, and stay disciplined with everyone who simply asks.

Put it in writing before it matters

Every element of this belongs in a founder agreement: the split, the vesting, each person’s role, and what happens if someone leaves. Write it while the founders still agree. The document is worth having precisely because it exists before any disagreement.

Get it right the first time

Equity is one of the few founder decisions that is genuinely hard to reverse, and it shapes every raise, every hire, and every exit that follows. A considered split, proper vesting, and a signed agreement are inexpensive protection against failure that originates inside the founding team.

This is worth structuring carefully and modelling on your cap table before you commit, so you can see how today’s split plays out three rounds from now. If you are dividing ownership, or reconsidering a split you have already made, book a conversation and we will help you settle the right position and get it recorded.