Startup Equity Dilution Calculator
What each round, SAFE and option pool does to who owns the company.
Who owns the company after each round
- Founders and common
- Options and pool
- Investors
Fully diluted. Before a priced round, SAFEs and notes are shown at their caps. Move over (or tap) a column for the figures.
Ownership after every round
“at the cap”: a SAFE or note before it converts, at the share its cap guarantees; the round decides the final number.
How this was calculated
Source: Y Combinator, Post-Money SAFE documents and User Guide. The example is the guide’s own worked example.
Round 1
Investors in this round
Results are estimates for general information and planning, not financial advice. Banks and institutions may calculate differently (rounding, fees, rate changes). Confirm figures with your lender or a qualified adviser before deciding.
About the Startup Equity Dilution Calculator
A cap table says who owns what share of a company. Enter today’s shares, options and option pool, then the rounds in order — post-money SAFEs, convertible notes and priced rounds — and the calculator works out every round the way the documents do: the price per share, the new shares for each investor, the option-pool top-up created before the round, the shares each SAFE and note converts into (cap, discount or round price, whichever gives more), and each holder’s fully diluted ownership after every step.
The page opens on the worked example from Y Combinator’s Post-Money Safe User Guide — two SAFEs and a 5 million Series A — and reproduces its cap table: founders 51.54%, the SAFE investors 3.28% and 9.06%, the Series A lead 20.00% and a 10.00% unallocated pool.
How to use it
- Under Cap table today, enter each holder and what they hold: shares, granted (and promised) options, or the unallocated option pool.
- Add the rounds in order: a post-money SAFE (amount, cap, discount), a convertible note (principal, interest, months until the round, cap, discount) or a priced round. Move rounds up or down with the arrows.
- For a priced round, enter the pre-money valuation, the option pool top-up (to a share of the company after the round, or a number of shares) and each investor and amount. An existing holder with the same name keeps one line.
- Read founders’ ownership, the price per share and the ownership after every round, and each round’s conversions.
- Copy cap tables or Download CSV for a spreadsheet.
Examples
Founders 9,250,000 · options 650,000 · pool 100,000 · pool top-up 1,695,000 shares
SAFEs: at least 200,000 ÷ 4M + 800,000 ÷ 8M = 15% Price = 15,000,000 ÷ (11,764,705 + 1,695,000) = $1.1144 After: founders 51.54% · Investor A 3.28% · Investor B 9.06% · Investor C 20.00% · pool 10.00%
Round price 1.875 → the SAFE converts at 1.50: 666,666 shares (5%) New money 2,666,666 shares (20%) · founders 75%
540,000 converts at 4,000,000 ÷ 8,000,000 shares = 0.50 (the cap beats 80% of the round price): 1,080,000 shares
Common uses
- See how much of the company the founders keep after a SAFE round and a Series A.
- Compare a higher valuation with a bigger option pool, or a cap with a discount.
- Check the shares an investor’s SAFE or note will convert into before the round closes.
- Prepare the ownership table for an investor update or a board meeting.
Pre-money, post-money and the price per share
- Pre-money valuation: what the company is worth just before the new money. It includes the shares the SAFEs and notes convert into and, usually, the option-pool top-up.
- Post-money valuation = pre-money + new money.
- Price per share = pre-money ÷ (fully diluted shares + converted SAFEs and notes + pool top-up). Each new investor gets amount ÷ price shares, rounded down. The YC guide states its example’s price to four decimals ($1.1144), and so does the calculator; untick the option to use the exact price.
The option pool top-up (the “option pool shuffle”) is created before the round, inside the pre-money, so it dilutes the existing holders and not the new investors. Choose a target — such as a 10% unallocated pool after the round — and the calculator solves for the shares, or enter the number of shares agreed.
How a post-money SAFE converts
At the priced round a post-money SAFE converts into whichever gives the most shares:
- the purchase amount ÷ the round’s price per share;
- the purchase amount ÷ the Safe Price = post-money valuation cap ÷ Company Capitalization;
- the purchase amount ÷ the discount price = round price × (100% − discount), for SAFEs with a discount.
Company Capitalization counts, just before the round, all shares, granted and promised options, the unallocated pool and every SAFE and note as converted — but not the pool top-up of the round. So a capped SAFE gets exactly amount ÷ cap of the company before the new money: 200,000 at a 4M cap is 5%. That share is then diluted by the round’s new money and its pool top-up, as the YC guide explains. Source: Y Combinator, Post-Money SAFE documents and User Guide.
Convertible notes
A note is a loan that converts into shares at the next priced round. The amount that converts is the principal plus the interest to that day (simple interest here: principal × rate × months ÷ 12). It converts at the lower of the cap price — the valuation cap ÷ the fully diluted shares before the round — and the discount price. Notes are written in many ways: some measure the cap against a capitalization that includes the new pool or the converting securities, some compound the interest. Check yours against the result.
Limitations
- Ownership is fully diluted: shares, granted options and the unallocated pool all count. Outstanding-share percentages are higher.
- Pre-money SAFEs, MFN terms, pro-rata rights, liquidation preferences, anti-dilution adjustments, warrants and secondary sales are not modelled.
- The pool top-up is taken as the agreed number or the target share; the YC exception for promised options larger than the existing pool is not applied.
- A planning aid, not legal or investment advice: the share numbers in the closing documents decide.
Privacy
Everything is worked out in your browser. The cap table and round terms you enter are never uploaded.
Frequently asked questions
How do I calculate dilution from a funding round?
New investors own new money ÷ post-money valuation; everyone else is multiplied by pre-money ÷ post-money. Raising 5M at 15M pre-money sells 25%, and a founder with 60% keeps 45% — less if an option-pool top-up comes out of the pre-money too.
How does a post-money SAFE convert?
Into the greater number of shares at the round price, at the Safe Price (post-money cap ÷ Company Capitalization) or at the discount price. With a cap, the investor owns amount ÷ cap of the company just before the round — 200,000 at a 4M cap is 5% — and is then diluted by the round itself.
What is the option pool shuffle?
Investors usually ask for the option pool to be enlarged before their money comes in, as part of the pre-money valuation. The new pool shares then dilute only the existing holders. The calculator solves for the top-up that leaves the pool at the share you choose after the round.
Do SAFE holders get diluted by other SAFEs?
With post-money SAFEs, no: each capped SAFE is fixed at amount ÷ cap of the Company Capitalization, which includes all the SAFEs. The founders take that dilution. All SAFE holders are diluted by the priced round’s new money and its pool top-up.
What is the difference between a valuation cap and a discount?
A cap sets the highest valuation the SAFE or note converts at; a discount gives a percentage off the round price. When the document has both, the investor gets whichever gives more shares. If the round values the company below the cap, the cap does not help and the round price (or the discount) decides.