How to Split Startup Equity Between Co-Founders
Splitting equity is one of the most important decisions founders make — and one of the most common sources of startup failure. A bad equity split creates resentment that compounds over years. The solution is a structured, transparent process where every factor is scored objectively.
The 5 Factors That Determine Fair Equity
| Factor | What It Measures | Typical Weight |
|---|---|---|
| Capital | Money invested into the company | 20-30% |
| Time | Hours per week committed (full-time vs part-time) | 25-35% |
| Experience | Relevant industry expertise and track record | 15-20% |
| Idea / IP | Who conceived the idea or brought intellectual property | 10-15% |
| Risk | Personal risk taken (quitting job, relocating, etc.) | 10-15% |
Why 50/50 Splits Often Fail
Equal splits feel fair in the early days when everyone is excited. But they ignore real differences in contribution. If one founder is full-time while the other keeps their day job, or one invested $50K while the other invested $0, a 50/50 split doesn't reflect reality. The Noam Wasserman study at Harvard Business School found that teams who split equity equally were significantly more likely to have founder disputes.
Always Add Vesting
Regardless of the split, add a vesting schedule. The standard is 4 years with a 1-year cliff: each founder earns 25% of their equity after year 1, then the rest vests monthly over 3 more years. Without vesting, a co-founder could leave after 3 months and still own 40% of your company. Vesting protects everyone.
For splitting ongoing profits (not equity), use our business profit split calculator. For revenue sharing arrangements, try the revenue share calculator.