Dilution Explained: A Founder's Walkthrough
Every time your startup issues new shares, your slice of the company gets smaller. That is dilution, and it is a normal part of raising money and hiring. The trick is to understand the math well enough to see it coming, negotiate the parts that matter and judge whether a smaller slice of a bigger company is a good trade.
Key takeaways
- Dilution happens when a company issues new shares, so each existing holder owns a smaller percentage, even though their number of shares stays the same.
- Ownership = your shares divided by the fully diluted share count. Always ask what "fully diluted" includes.
- An option pool created before a round is funded comes out of the existing holders' share, which lowers your effective valuation.
- Dilution is fine when the value of your stake grows. The question is not "how much do I own?" but "what is my stake worth, and what did we get for it?"
Founders often learn about dilution the hard way, by looking at a cap table after a round and wondering where ten percent of their company went. The numbers are not mysterious. They follow a few simple rules, and once you have walked through them with a worked example, you will read a term sheet differently.
This walkthrough follows one made-up startup from founding through a seed round and a Series A. Every figure is invented for illustration. Real deals involve legal documents and tax questions that vary by country, so treat this as general information, not legal, tax or investment advice, and work with a startup lawyer and an accountant on your own numbers.
What dilution actually is
Imagine your company is a pizza cut into a fixed number of slices. If you own 7 slices out of 8, you own 87.5% of the pizza. Now the company issues 2 new slices to an investor. You still own 7 slices, but there are now 10 in total, so you own 70%.
That is all dilution is: your share count stays the same while the total grows. What changes the picture is that the investor paid money for those slices, and that money is supposed to make the whole pizza bigger.
Where new shares come from
- Priced equity rounds, where investors buy newly issued preferred shares.
- Convertible instruments, such as SAFEs and convertible notes, which turn into shares at a later round.
- Employee option pools, reserved shares for future hires and advisers.
- Warrants, for example those sometimes attached to venture debt.
The one formula you need
Ownership % = your shares divided by fully diluted shares.
"Fully diluted" usually counts all issued shares plus all options, warrants and convertible instruments as if they had turned into shares. Definitions vary between documents, so always ask what is included.
A walkthrough: from founding to Series A
Meet a made-up startup with two founders. All share counts, valuations and amounts below are invented examples.
Stage 1: Founding
The two founders split 7,000,000 shares between them. They own 100% of the company together. Following a common pattern, their shares vest over 4 years with a 1-year cliff, which is a rule of thumb rather than a requirement.
Stage 2: A seed round with an option pool
A lead investor offers $2,000,000 at an $8,000,000 pre-money valuation, so the post-money valuation is $10,000,000 and the investor will own 20% after the round. The investor also asks for an unallocated option pool equal to 10% of the company after the round, created before the new money goes in.
- Work out the pool size. The founders will own 70% after the round (100% minus 20% for the investor minus 10% for the pool). Their 7,000,000 shares are 70% of a total of 10,000,000 shares. So the pool is 1,000,000 shares.
- Find the pre-money fully diluted count. Founders' 7,000,000 plus the new 1,000,000 pool equals 8,000,000 shares.
- Find the price per share. Pre-money valuation divided by pre-money fully diluted shares: $8,000,000 divided by 8,000,000 equals $1.00.
- Find the investor's shares. $2,000,000 divided by $1.00 equals 2,000,000 new shares.
- Check the result. 7,000,000 plus 1,000,000 plus 2,000,000 equals 10,000,000 shares. Founders 70%, pool 10%, investor 20%.
Common mistake
Assuming the option pool is "the investor's problem." When the pool is created in the pre-money, the whole dilution from it falls on existing holders. Without the pool, these founders would have owned 80% after the round instead of 70%. Put another way, the headline is $8 million pre-money, but the founders' shares are effectively valued at $7 million. This is often called the option pool shuffle.
Stage 3: Series A
Eighteen months later, a new investor offers $6,000,000 at a $24,000,000 pre-money valuation, for a $30,000,000 post-money valuation. To keep the example simple, assume no pool top-up this time.
- Price per share: $24,000,000 divided by 10,000,000 shares equals $2.40.
- New shares: $6,000,000 divided by $2.40 equals 2,500,000.
- New total: 12,500,000 shares.
The new investor owns 20%, and everyone else is diluted by the same proportion: each existing holder keeps 80% of their previous percentage.
The ownership table, round by round
Here is the whole walkthrough in one table. Copy the layout into a spreadsheet to model your own rounds. All figures are made-up examples.
| Holder | After founding | After seed | After Series A | Value of stake after Series A (example) |
|---|---|---|---|---|
| Founders (7,000,000 shares) | 100% | 70% | 56% | $16,800,000 |
| Option pool (1,000,000 shares) | 0% | 10% | 8% | $2,400,000 |
| Seed investor (2,000,000 shares) | 0% | 20% | 16% | $4,800,000 |
| Series A investor (2,500,000 shares) | 0% | 0% | 20% | $6,000,000 |
The founders went from 100% to 56%. But at the seed price, their 7,000,000 shares were worth $7,000,000 on paper. At the Series A price, the same shares are worth $16,800,000 on paper. Their slice shrank while the pizza grew faster.
Pro tip
Build a "next round" column into your model before every raise. Seeing how today's terms will look after one or two future rounds helps you spot when a large pool or a low valuation will leave the founding team with too little ownership to stay motivated.
The other sources of dilution
SAFEs and convertible notes
These instruments convert into shares at a later priced round, often at a discount or subject to a valuation cap. Founders sometimes stack several of them and forget to model the combined effect. When they all convert at once, the dilution can be larger than expected, so model each one's conversion before you sign the next.
Pool top-ups
Later investors may ask you to refresh the option pool before their round, repeating the shuffle described above. Push for a pool sized to a real hiring plan for the next 12 to 18 months rather than a round number.
Anti-dilution protection
Preferred stock often includes anti-dilution terms that adjust the investor's conversion price if a future round is priced lower (a down round). Broad-based weighted average adjustments are generally gentler on founders than full ratchet terms. Ask your lawyer to model the effect of each version on your ownership.
Pro rata rights
Some investors have the right to buy enough shares in future rounds to keep their percentage. This does not dilute founders more in itself, but it affects how much room new investors have and can shape the next round.
How to manage dilution without obsessing over it
- Raise what you need for clear milestones. More money now means more dilution now. Tie the amount to what gets you to a stronger position.
- Negotiate the pool, not just the valuation. A slightly lower valuation with a smaller, justified pool can leave you better off.
- Model every convertible. Keep a live sheet of all SAFEs and notes and their conversion terms.
- Watch the whole stack. Liquidation preferences and participation rights can matter as much as percentages at exit.
- Think in value, not percent. Ask what your stake is worth after the round and what the new capital lets you build.
Hypothetical example
Two founders receive competing seed offers. Offer A is a $10 million pre-money with a 15% post-money pool created in the pre-money. Offer B is a $9 million pre-money with a 10% pool, both raising $2 million. Using the same method as above, Offer A leaves the founders with about 68% after the round, and Offer B leaves them with about 72%. The "higher" valuation turns out to be the more dilutive offer. They choose B after confirming with their lawyer that the smaller pool covers their hiring plan.
Your dilution checklist
- List every holder, option, warrant, SAFE and note in one sheet
- Confirm what "fully diluted" means in each document
- Model the option pool in the pre-money and the post-money
- Size the pool to a written hiring plan for the next 12 to 18 months
- Model how all convertibles will convert at the next round
- Add columns for one or two future rounds
- Ask your lawyer to explain anti-dilution and pro rata terms
- Compare offers on founder ownership and stake value, not headline valuation
Frequently asked questions
Is dilution always bad for founders?
No. Dilution is the price of capital and talent. It is a good trade when the money or people raise the company's value by more than the percentage you give up. It becomes a problem when you raise more than you need or at terms that leave too little for the team.
How much dilution is normal in a round?
It varies widely by stage, sector, market conditions and how much is raised. Rather than chasing a benchmark, model your own rounds and make sure the founding team keeps enough ownership to stay motivated through several more raises.
Do employees get diluted too?
Yes. Employees holding shares or options are diluted by new rounds in the same proportion as other holders. Explaining this clearly when you grant options builds trust.
Can I avoid dilution entirely?
Only by not issuing new shares, which means funding growth from revenue or debt. Some founders do this successfully, while others find that equity is the only way to grow fast enough. Both are valid choices.
Related reading
The bottom line
Dilution is just arithmetic: your shares divided by a growing total. Walk through each round with a simple table, pay special attention to the option pool and convertibles, and compare offers on what you will actually own afterward.
A smaller slice of a much bigger company is usually a great outcome. Build your model before your next raise, ask your lawyer to check the terms, and you will negotiate from understanding rather than surprise.
