PureBuild Logo
PureBuild.xyz
BLOGTOOLS
GitHubAbout Maker
  1. Home
  2. Blog
  3. The Mathematics of Founder Equity
BACK TO LOGS
2025-12-28 • PureBuild • 3 min read

The Mathematics of Founder Equity

Why the 50/50 split is a mathematical error, and how to use game theory to prevent dead equity.

Share:

The 50/50 Lie

When two co-founders start a company, the default conversation usually goes like this:

"We're partners. 50/50?" "Deal."

This is the first mistake. It feels "fair" emotionally, but it is incorrect mathematically.

Why 50/50 Fails

Equity is not a reward for friendship. It is a reward for risk and execution. A 50/50 split implies a perfectly symmetrical future:

  1. Both founders will take identical risk.
  2. Both founders will add identical value.
  3. Neither founder's life circumstances will change.

This is a statistical impossibility.

The Alternative: Dynamic Splits

Instead of a static snapshot, view equity as a dynamic ledger. The "Slicing Pie" model (invented by Mike Moyer) suggests allocating equity based on the fair market value of contributions.

If Founder A puts in $50k cash and Founder B puts in $0 but works full-time:

  • Cash is liquid and high risk.
  • Labor is illiquid but high value.

You need a multiplier. Typically, cash gets a 4x multiplier (because it's scarce) and unpaid labor gets a 2x multiplier.

Dead Equity and The Cliff

The bigger danger than the split itself is Dead Equity. This happens when a co-founder leaves with a large chunk of the cap table, rendering the company uninvestable.

The standard solution is Vesting with a Cliff:

  • 4 Year Vesting: You earn your shares over 48 months.
  • 1 Year Cliff: If you leave before month 12, you get 0%.

This isn't just legalese; it's a mechanism to filter for commitment.

The Dilution Trap

Founders often obsess over their percentage ownership rather than the value of the underlying asset.

Use our Equity Calculator to run this scenario:

  1. You own 50% of a $2M company. Value = $1M.
  2. You raise money and own 30% of a $10M company. Value = $3M.

You own less of the company, but you are richer. This is the only math that matters.

If you are optimizing for control (percentage), you are building a lifestyle business. If you are optimizing for outcome (value), you must welcome dilution as the cost of growth.

Calculating Your True Worth

Don't just look at the gross value of your shares. You must calculate the Net Value:

Net Value = (Share Price * Shares) - (Strike Price * Shares) - Taxes

Many employees at "unicorns" realize too late that their high strike price + taxes makes their options worthless, even at a high valuation.

Check the math yourself on the Equity Calculator. Don't trust the offer letter's "potential value." Trust the numbers.

Try these related tools:

Equity CalculatorRunway CalculatorDilution Simulator

Related Articles

2025-12-28

Capital Table Logic

2025-12-28

The Price of Your Time

Stay Updated

500+ founders

New tools, deep dives, and startup insights. No spam, unsubscribe anytime.

Join the discussion

Have thoughts on this? Ping me on Twitter.

@yewlne7
Share:

Tools

  • View All Tools →
  • Equity Calculator
  • Dilution Simulator
  • Runway Calculator
  • Unit Economics

More Tools

  • Hourly Rate
  • Net Revenue
  • API Cost Estimator
  • Capacity Planner
  • Viral Coefficient
  • Launch Timing ✦

Learn

  • All Articles →
  • Equity Math
  • Dilution Logic
  • Magic Number
  • K-Factor Guide
  • RSS Feed

Connect

  • Twitter
  • GitHub

No spam. Unsubscribe anytime.

© 2026 PureBuild • Crafted with logic, not AI

HomeBlogSitemap