How should I split equity with my cofounder?

Equity splits should reflect actual contributions, not just equal division. Consider who is funding the business, who quit their job first, who owns the product vision, who is building the product, who will lead long-term, and who brings irreplaceable expertise. Use a weighted approach rather than defaulting to 50/50.

What is the most common startup cofounder equity split?

Common patterns include 50/50 for two cofounders starting full-time on the same day, 60/40 when one founder quit earlier or brought funding, 70/30 for a full-time operator plus a part-time support cofounder, and 90/10 when one person had the idea and traction while the other joined for scaling.

When should I have the equity conversation with my cofounder?

Have the equity conversation early, before you start working together full-time. If you're scared to talk about it now, you're not ready to split anything. The conversation should happen after you understand what each founder is actually committing.

Should cofounders always do a 50/50 equity split?

No. Equal doesn't always mean fair, and fair doesn't always mean equal. A 50/50 split works when both founders started at the same time, took the same risk, and bring comparable value. But it can create deadlock in decision-making and resentment if one founder contributes significantly more.

How Much Startup Equity Should I Give My Cofounder?

100% of startup equity in nothing is still nothing. But how you split equity between cofounders sets the tone for how founders show up today and five years from now.

This isn't just about percentages. It's about ownership, trust, and what happens when the shine wears off. A few percent might not matter now, but they will when things get hard.

This page is built to help you:

Think before you split
Avoid the scar tissue of misaligned equity
Use the calculator as a mirror, not a scoreboard

The calculator below doesn't give you the answer. It helps you ask the questions most founders avoid. It challenges your assumptions with counter-arguments at every step. It's designed to surface misaligned expectations before they cost you your company.

What This Cofounder Equity Calculator Does (and Doesn't Do)

This calculator helps you:

Structure an equity split conversation around 10 real dimensions
See which founder is carrying what weight across different factors
Challenge your own assumptions with counter-arguments at every step
Get a weighted, evidence-based starting point for the conversation

But it won't:

Give you legal advice
Tell you who's "right"
Replace a frank conversation with your cofounder
Predict how people will evolve over time

It's a compass, not a contract. Use it wisely.

How to Decide How Much Equity to Give a Cofounder

Equity sets tone, trust, and future power. It's never "just paperwork."
Equal doesn't always mean fair. Fair doesn't always mean equal.
Don't split until you understand what each founder is actually committing.
This calculator helps make that invisible work visible.
If you're scared to talk about it now, you're not ready to split anything.

Common Cofounder Equity Splits (With Examples)

There's no universal right answer, but these are real-world patterns that come up again and again:

50/50 - Two technical cofounders starting full-time on day one
60/40 - One cofounder quit earlier, built MVP, or brought funding
70/30 - Operator + capital vs a part-time support cofounder
90/10 - One person had the idea and traction; the other joined for long-term scaling
33/33/33 - Three cofounders with matching time, skill, and early commitment

These examples aren't formulas. They're conversation starters. Use the calculator below to see where your real contributions lie.

Do You Actually Want a Cofounder?

Many founders default to "I should have a cofounder" because:

It's what YC or Techstars say
It's lonely
It feels safer

But bringing on a cofounder is a permanent relationship. Before you decide how much to give them, ask:

3 Questions That Matter:

Are you looking for skills or emotional safety?
Is this person filling a gap? Or just making the journey feel less risky?
Would you still want them on the cap table in 5 years?
Even if they leave? Even if they disagree with you?
If you got hit by a bus, would you trust them to run the company?
If not, you may not have a cofounder. You may have a helper.

If you're not ready to answer those honestly, you're not ready to split anything.

Cofounder Equity Models (And When They Work)

There's no perfect formula. But there are 6 common models:

1. Equal Split (50/50)

Best when:

You started together, full-time, same day. No questions, no power imbalance.

Risk:

If one founder drifts or doesn't scale, resentment builds. Fast.

2. Weighted Split (Points-Based)

Best when:

You want to score the relationship across roles, risk, time, and value.

Risk:

Overcomplicating the early stage, or underweighting future risk.

3. Founder Value Today vs Future

Best when:

One founder is doing the work now, the other is showing up later or in bursts.

Risk:

You may underestimate how valuable one founder becomes over time.

4. Time-Based Cliff or Vesting

Best when:

You don't fully know if they'll commit but want to create an option.

Risk:

They don't last. Then you're left with a messy breakup or wasted cap table space.

5. Dynamic Equity Model (e.g. Slicing Pie)

Best when:

You're both contributing unevenly over time and want to track input precisely.

Risk:

Very few founders have the operational discipline to track time, capital, risk, and value consistently.

6. Buy-In or Silent Co-Founder

Best when:

Someone's bringing money, IP, or a network but not full-time energy.

Risk:

You misread how much equity is worth when someone isn't in the trenches.

Cofounder Equity Calculator

10 questions every startup founder should answer before splitting equity. Every answer gets challenged. The result is a conversation starter, not a verdict.

Startup Co-Founder Equity Calculator

10 questions. Each one surfaces a dimension of your co-founder relationship that most founders avoid talking about. After each answer, you'll see the argument for your position and the counter-argument against it.

Honest

Every answer gets challenged

Weighted

Some factors matter more

Tactical

Actionable result + warnings

This is a conversation starter, not a legal document. Use it as a mirror, not a scoreboard.

Why Founders Get Equity Splits Wrong

They're afraid of being unfair
They split too early, without knowing roles
"Equal split" to avoid hard conversations
They use the past to justify the future
They underprice the person who's in the trenches

This tool is designed to surface misaligned assumptions, under-acknowledged risk, and emotional labor that rarely gets valued.

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