The Free Startup Equity Calculator Suite
Every founder needs to answer three questions about equity: How do we split it? How does it change over time? What's it worth at the end? A startup equity calculator helps you answer all three — without paying a lawyer $500/hour to run the numbers.
We built 25+ free equity calculators at FounderMath so founders can model their equity from day one through exit. This guide covers the six most important calculations you need, with links to the free tools that handle each one.
Start with Your Free Equity Report
Enter your startup details and get an instant equity dilution report with your personal Equity Score (0-100), benchmarks, and recommendations.
Get Your Free Equity Report →1. Founder Equity Split Calculator
The first equity question every founding team faces: how do we divide the pie? This isn't just about who had the idea — it's about ongoing contribution, risk, and alignment.
How to Split Equity Fairly
The most common splits for startups:
- Solo founder: 100% (but consider 10-15% option pool early)
- Two cofounders: 50/50 or 60/40 (if one contributes significantly more)
- Three cofounders: 33/33/33 or 40/35/25 (based on roles)
- Four+ cofounders: Rarely recommended — equity gets too thin after dilution
Example Calculation
Two technical cofounders, one business cofounder: 35% / 35% / 30% with 4-year vesting and 1-year cliff. Each cofounder also gets a board seat to protect their stake.
Key factors that should influence your split: time commitment (full-time vs part-time), cash investment, IP contribution, domain expertise, and network/connections. Use our Equity Split Calculator to model different scenarios.
2. Equity Dilution Calculator
Every time you raise money, your ownership percentage goes down. This is dilution — and if you don't model it upfront, you might be shocked at how little you own after Series B.
How Dilution Works
Here's the basic formula: when investors buy 20% of your company, every existing shareholder (including you) gets diluted by 20%. Add an option pool on top, and the dilution compounds.
Example: Two Rounds of Dilution
You start with 33% (3 cofounders, equal split).
Seed round: 20% to investors + 10% option pool → you drop to 23.1%
Series A: 25% to investors + 5% pool refresh → you drop to 16.4%
Total dilution: 16.6 percentage points (50% of your original stake)
Our Equity Dilution Calculator lets you model exactly this — enter your starting equity, planned rounds, and see your ownership at every stage. It's free and takes 30 seconds.
3. SAFE Note Calculator
If you're raising a pre-seed or seed round, there's a good chance you're using a SAFE (Simple Agreement for Future Equity). But how much equity will your SAFE investors actually get? That depends on the valuation cap, discount rate, and your next priced round.
SAFE Conversion Math
A SAFE converts to equity at the lower of: (1) the valuation cap price, or (2) the discounted next-round price. This means a $500K SAFE with a $5M cap buys 10% of your company — before the new money even arrives.
Example: SAFE with Cap + Discount
Investment: $250K | Cap: $5M | Discount: 20%
Next round: $10M pre-money at $2.50/share
Discounted price: $2.00/share → SAFE investor gets 125,000 shares
Effective ownership: 2.5% for $250K
Model your SAFE rounds with our SAFE Calculator — enter the cap, discount, and investment to see exactly how much equity your SAFE holders will own after conversion.
4. Vesting Schedule Calculator
Equity isn't just about how much you get — it's about when you actually own it. Standard startup equity vests over 4 years with a 1-year cliff. Leave before the cliff? You get nothing. Leave after 2 years? You keep half.
How Vesting Works
| Year | Vesting Event | Cumulative Vested | What Happens If You Leave |
|---|---|---|---|
| 0-1 | Cliff period | 0% | You get nothing |
| 1 | Cliff vests | 25% | You keep 25% (1/4 of shares) |
| 2 | Monthly vesting | 50% | You keep 50% |
| 3 | Monthly vesting | 75% | You keep 75% |
| 4 | Fully vested | 100% | You keep everything |
Use our Vesting Calculator to see exactly how many shares you've earned at any point, including acceleration scenarios (single-trigger vs double-trigger).
5. Runway & Burn Rate Calculator
Your runway is how many months you can survive before running out of cash. Why does this matter for equity? Because running out of runway means raising at a worse valuation — which means more dilution for you.
Runway Formula
Runway (months) = Cash in Bank / Monthly Burn Rate
Example
Cash: $1.2M raised | Burn: $80K/month (3 engineers + hosting)
Runway: 15 months
If you need 6 months to fundraise, you should start raising at month 9 — when you still have $720K in the bank and leverage to negotiate.
Calculate your exact runway with our Runway Calculator. It accounts for revenue, expenses, and fundraising timing.
6. Exit Value Calculator
The question every founder really wants answered: what's my stake worth at exit? The answer depends on your final ownership percentage and the exit valuation.
Exit Value Formula
Your Exit Value = Your Ownership % × Exit Valuation
Example: $100M Exit
You own 16.4% after dilution (see example #2)
Your exit value: $16.4M before taxes and liquidation preferences
With 1x non-participating liquidation preference on $15M invested, investors take $15M first, then you get your pro-rata of the remaining $85M. Your actual payout: $13.94M
Our Equity Report calculates your exit value across multiple scenarios — and shows how liquidation preferences, participation, and option pools affect your actual payout.
All 25+ Free Equity Calculators
Beyond the six core calculations above, here are the other free tools available on FounderMath:
📈 Equity Dilution Calculator
Model your ownership after every funding round. See pre-seed through Series B+ dilution.
Calculate Dilution →💰 SAFE Note Calculator
Model SAFE conversion with valuation caps, discounts, and MFN provisions.
Calculate SAFE →📅 Vesting Schedule Calculator
See exactly when your shares vest, with cliff and acceleration scenarios.
Calculate Vesting →⏱ Runway Calculator
How many months until you need to fundraise? Account for burn, revenue, and growth.
Calculate Runway →📊 Cap Table Builder
Build your cap table from scratch. See ownership at every round with pro-rata calculations.
Build Cap Table →🎯 Equity Split Calculator
Split founder equity based on contribution, role, and commitment level.
Split Equity →See all tools on our Free Startup Tools page, or explore the Equity Cheat Sheet for quick reference.
Startup Equity Calculator vs. Paying a Lawyer
Founders often ask: "Do I need a lawyer to calculate my equity?" The answer: you need a lawyer to draft legal documents, but you don't need one to understand the math.
| Task | DIY Calculator | Lawyer ($300-600/hr) |
|---|---|---|
| Model dilution across rounds | Free, instant | $500-1,500 |
| SAFE conversion math | Free, instant | $500-1,000 |
| Vesting schedule | Free, instant | Included in incorporation |
| Exit scenario modeling | Free, instant | $1,000-3,000 |
| Draft legal documents | Not available | Required for legal validity |
| Negotiate term sheets | Education only | Recommended |
Use calculators to understand the math and make informed decisions. Then hire a lawyer to make it legal. Our Equity Glossary covers 50+ terms you'll encounter in those conversations.
Common Startup Equity Mistakes
After analyzing thousands of equity scenarios, these are the mistakes we see most often:
- Not modeling dilution before raising. Founders are surprised when they own 12% after Series B. Model it upfront.
- Equal splits without vesting. 50/50 sounds fair until one cofounder leaves after 6 months with half the company. Always use 4-year vesting.
- Ignoring the option pool. Investors typically require a 10-20% option pool — and it comes out of your equity, not theirs.
- Not understanding liquidation preferences. A 2x participating preferred means investors get paid twice before you see a dime. Learn how liquidation preferences work.
- Raising too much too early. More money = more dilution. Raise what you need, not what you can.
Our free equity report flags these issues automatically based on your inputs.
What's Your Equity Score?
We created the FounderMath Equity Score — a single number from 0-100 that summarizes your equity position. It factors in:
- Ownership retention (40%): How much equity you keep after all rounds
- Dilution vs benchmarks (35%): How your dilution compares to industry averages
- Exit potential (25%): Your projected payout relative to your goals
A score of 80+ means your equity position is strong. Below 40? You should re-evaluate your fundraising strategy. Get your score free in the Equity Dilution Report.
Get Your Free Equity Report with Score
Enter your startup details and get a personalized report with your Equity Score, round-by-round dilution, benchmarks, and actionable recommendations. No signup required for the free preview.
Get Your Free Report →Further Reading
- Startup Equity Cheat Sheet — Quick reference for all key terms and formulas
- Equity Glossary — 50+ startup equity terms explained
- Equity Benchmarks by Stage — Industry data on founder ownership at each round
- Convertible Notes Guide — How convertible notes work with examples
- Free Dilution Calculator — Step-by-step dilution walkthrough
- All Blog Posts — 90+ guides on startup equity