How to split equity with a co-founder

Start with the partnership ahead, not the work behind

Founder equity should primarily reflect the years of contribution, responsibility, and risk still ahead. An idea, domain name, prototype, or early customer can matter, but those assets rarely outweigh the ongoing work required to build a durable company.

Discuss expected roles, time commitment, cash investment, relevant intellectual property, personal guarantees, and opportunity cost. The purpose is not to assign a price to every task. It is to expose assumptions before percentages make them feel permanent.

Equal can be fair—but it should be deliberate

A roughly equal split can reinforce a genuine long-term partnership when founders are joining at the same stage with comparable commitment and responsibility. It can also create resentment when one person is part-time, carrying less risk, or expected to leave after a narrow contribution.

If the split is unequal, explain why in language both founders would consider fair even if their roles were reversed. Avoid tiny differences designed only to signal who is in charge; decision authority can be defined directly in governance documents.

• Compare future time and operating responsibility.
• Document cash and intellectual-property contributions.
• Separate economic ownership from specific decision rights.

Use vesting to protect both founders

Vesting allows equity to be earned over time, commonly with an initial cliff followed by monthly vesting. If a founder leaves early, unvested shares return to the company instead of remaining with someone who is no longer contributing.

Discuss acceleration during an acquisition, treatment of a founder who is terminated, and what happens during illness or extended leave. These scenarios deserve advice from qualified startup counsel in the company’s jurisdiction.

Create a process for roles that change

Founder responsibilities almost always evolve. Equity should not be renegotiated every time a job title changes, but the team needs a process for sustained changes in commitment, new capital contributions, or a founder moving away from daily operations.

Write the reasoning down, use appropriate legal documents, and revisit expectations at defined milestones. A thoughtful equity conversation is less about discovering a perfect number than proving the founders can navigate a consequential disagreement together.