How do you split equity between co-founders? Decide it early, in writing, based on what each founder actually contributes — capital, full-time commitment, IP, and expertise — and protect the company with a vesting schedule. Equity is one of the few decisions made when the company is worth nothing that shapes every dollar it ever produces. While it is just two or three of you around a table, changing the split is a conversation and a document. After your first investor comes in, the same change requires consent from more parties, can trigger tax events, and sometimes is simply impossible. That is why founders of a hardware startup should close this question before raising a dime.

Why an automatic 50/50 split is usually a mistake

Equal splits get chosen because they are comfortable, not because they are right. In most ventures the contributions are not equal: one founder puts in cash, another quits a job to go full time, a third brings the patent or the core technology. An equal split that ignores those differences creates quiet resentment that erupts at exactly the worst moment — before a round, in front of an investor, or when deciding who stays. A useful discipline: be able to explain why you chose every number. If you have no rationale, you have not finished the conversation.

Practical methods for setting the percentages

  • Weighted contributions. List the factors that matter — idea and IP, cash invested, full-time vs part-time commitment, relevant experience, market connections, personal risk — assign each a weight, and score every founder. The result is not sacred, but it converts an emotional argument into a discussion about numbers.
  • Opportunity cost. Translate what each founder gives up — salary not taken, money invested, equipment contributed — into dollars, and split by the ratio. Especially useful when one founder keeps a day job while another goes all in.
  • Dynamic splits. Percentages accrue over time based on actual inputs rather than being fixed on day one. More accurate, but it demands disciplined tracking and up-front agreement on the counting rules.
  • Separate ownership from repayment. A founder who injects cash can take part of it back as a founder loan rather than extra shares, and a founder contributing extra hours can accrue deferred salary. That keeps equity reflecting the long-term partnership rather than a running tab.

Vesting: the mechanism that saves the company from a departing founder

The biggest danger is not the split itself but a founder who holds a large stake and walks away after six months. A dormant founder with a big block of dead equity kills fundraising — venture investors simply will not touch a cap table like that. The standard fix is founder vesting: shares are earned gradually over a multi-year schedule, with an initial cliff before the first tranche vests and monthly vesting afterward. Add acceleration provisions for an acquisition, and clear definitions of voluntary departure versus termination. All of it belongs in a founders' agreement drafted with a startup attorney, alongside a clause assigning all intellectual property to the company — a perfect equity split is worthless if the patent is registered in one founder's personal name.

Common mistakes we see repeatedly

  • Postponing the conversation. "We'll sort it out later" turns into a hard negotiation exactly when there is finally something to divide.
  • Paying for one-time services with equity. An advisor, designer, or vendor who takes a slice of the company stays on the cap table forever. Pay cash where you can; where you cannot, use small, vested advisor grants.
  • Forgetting employees and investors. Reserve an option pool early, and understand that your first round will dilute everyone — the mechanics are explained in pre-money vs post-money valuation and in our guide to pre-seed vs seed rounds.
  • Not documenting. A verbal understanding between partners is a lawsuit in waiting. Put the split, vesting, roles, and IP assignment in writing before the company has value.

How investors read your cap table

An investor evaluating you is not looking for a split that is "fair" in a moral sense — they are looking for a structure that lets the company win: active, motivated founders, no dead equity, live vesting, and a clean cap table. A short, confident explanation of the logic behind your numbers sounds far better than defensiveness. Equity structure also interacts with your funding instruments — see how a SAFE works — and with your overall plan for funding a hardware startup. If you are still proving the product, keep burn low with a lean hardware MVP while you settle the foundations. And since equity documents have real legal and tax consequences, have a startup attorney paper the final agreement — this article is educational, and Projects House is an engineering firm, not a law firm.

Building a physical product with co-founders? Talk to Projects House — we help founding teams turn a shared idea into an engineered, manufacturable product, with development milestones that keep investors and co-founders aligned.