Startup equity dilution: What it is, when it happens, and how it affects you
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When a startup issues new shares, your ownership percentage drops. That is dilution, and if you hold stock options, understanding how it works is one of the most practical things you can do to protect and plan around your equity.
Dilution does not mean you lose shares — you still own the same number. But because the total share count grows, your slice of the company shrinks.
The good news: dilution is usually tied to events that raise the company's valuation, which can increase the dollar value of your stake even as the percentage falls.
This guide breaks down how stock dilution works, when it happens, how to calculate it, and what you can do about it.
Dilution occurs when a company issues new shares of stock, increasing the total share count. While you still own the same number of shares, your ownership percentage of the company decreases.
Here is a simple example:
Your number of shares stayed the same, but the pie got bigger, so your slice is now a smaller percentage of the whole.
This table illustrates the impact across a funding round where the company's valuation also increased:
| Factors | Before round | After round |
|---|---|---|
Your shares | 100,000 | 100,000 |
Total shares | 50,000,000 | 100,000,000 |
Your ownership | 0.20% | 0.10% |
Company valuation | $250M | $1B |
Value of your stake | $500,000 | $1,000,000 |
Even though your ownership percentage was cut in half, the value of your stake doubled because the company's valuation quadrupled. That is the core dynamic of dilution at a growing startup.
Dilution is a common occurrence with startups, and it is not always a cause for concern. The key question is whether the company's valuation is growing faster than your ownership is shrinking.
The dilution formula is straightforward:
New Ownership % = (Your Shares / New Total Shares) x 100
Let's walk through a worked example.
Suppose you were granted 50,000 stock options at a startup with 10 million total shares outstanding. Before you factor in dilution, your potential ownership is:
(50,000 / 10,000,000) x 100 = 0.50%
Now your company raises a Series B and issues 5 million new shares to investors. The total share count grows to 15 million. Your new ownership percentage is:
(50,000 / 15,000,000) x 100 = 0.33%
Your ownership dropped from 0.50% to 0.33%. That is a 33% reduction in your percentage stake. But if the Series B valued the company at a much higher valuation, the dollar value of your 0.33% could still be larger than your original 0.50% was worth.
To calculate how much dilution you experienced as a percentage:
Dilution % = ((Old Ownership % - New Ownership %) / Old Ownership %) x 100
Using our example: ((0.50 - 0.33) / 0.50) x 100 = 34% dilution
The important number to track is not just your ownership percentage, but the price per share and the company's total valuation. Your cap table should show both. If you do not have access to your cap table, ask your company's finance or people team for your current share count and the total shares outstanding.
When you see "fully diluted shares" on a cap table or in a term sheet, it refers to the total number of shares that would exist if every outstanding option, warrant, and convertible security were exercised or converted into common stock.
This number includes:
Why does this matter? Because your ownership percentage should be calculated against the fully diluted share count, not just the shares that have been issued so far.
If a company tells you that you own 0.50% of the company based on 10 million shares outstanding, but the fully diluted count is actually 12 million (because of unexercised options and convertible notes), your real ownership is closer to:
(50,000 / 12,000,000) x 100 = 0.42%
Always ask for the fully diluted share count when evaluating your equity. The number on your grant letter alone does not tell the full story. Your company's cap table is the most reliable source for this figure.
Shareholders' percentage ownership can be diluted in several scenarios, with fundraising rounds being the most common.
Fundraising rounds: Startups sell new shares to raise money for growth or to pay down debt. Each time new shares are issued, existing shareholders' stakes are diluted. This happens at Series A, B, C, and beyond. For a deeper look at how each round can affect your options, see How does raising a new round affect stock options?.
More preferred stock issued. Employees and founders typically receive common stock, while investors like VCs are issued preferred stock with more favorable terms. Even if only preferred shares are issued during a round, common shareholders' ownership percentage is still diluted because the total share count increases.
IPOs. When a company goes public, new shares are often issued to raise capital. This dilutes all existing shareholders, including employees.
Your stake can also be diluted when:
If you are wondering whether an upcoming round will dilute you, our article on Am I about to get diluted? walks through the signals to watch for.
As long as your company's valuation growth outpaces dilution, the value of your equity remains positive. In other words, if the relative size of your slice shrinks (dilution), you can still come out ahead if the overall pie grows enough (increased valuation). For most startup employees at growing companies, this is the typical outcome.
Let's return to our example:
Here is how that works:
Maeve by Secfi can help you understand better conceptually different funding scenarios and plan around dilution by modeling exit values and different share prices.
To understand how dilution interacts with the value of your options specifically, see Calculate the value of your startup stock options.
Beyond your ownership percentage, dilution has a few additional effects worth understanding.
Down rounds. When all goes well for a startup, it will have a higher valuation in each subsequent round of financing. But "down rounds" happen. A down round is when a company sells stock at a price per share below the price in an earlier financing round, resulting in a lower valuation. For example, Airbnb raised $1 billion in April 2020 after lowering its internal valuation to $26 billion. Investors in that round received warrants exercisable at an $18 billion valuation, well below the company's prior valuation. In a down round, dilution hurts more because the valuation did not grow enough (or declined) to offset the new shares issued.
Voting power. Dilution can also reduce your voting power. If your shares come with voting rights, you are granted a certain number of votes per share. Voting typically gives you the ability to elect directors to the board and express your views about major corporate decisions, such as mergers and acquisitions. As your stake in the company declines, so does your voting power.
You cannot avoid dilution entirely at a startup, but there are ways to limit its impact:
Anti-dilution provisions — Contractual protections (usually in preferred stock agreements) that adjust the conversion price if new shares are issued at a lower price. Employees rarely have these, but understanding them shows why investor stock is better protected.
Pro-rata rights — The right to invest in future rounds to maintain your ownership percentage. Mostly available to investors, but worth asking about if you are an early employee with a significant stake.
Refresh grants — Additional stock option grants issued over time to offset dilution. If your company has been through several rounds since your initial grant, ask HR about refresh or top-up grants.
Negotiate on fully diluted count — When joining or receiving a new grant, ask for the fully diluted share count. A grant of 10,000 options means very different things at 5 million vs. 50 million fully diluted shares.
Monitor your cap table — Stay informed about total shares outstanding and how they change over time. Use tools like Maeve to track your ownership across funding rounds.
Secfi is a financial platform built for startup employees who hold stock options or equity. We help you understand, plan around, and act on your equity at every stage.
Here is what you can do with Secfi:
Get started for free or try Maeve to model your dilution scenarios now.
It depends on the context. Dilution is a normal part of startup growth. When a company raises a new round, it typically does so because it needs capital to grow. If that growth increases the company's valuation enough, the dollar value of your shares can increase even as your percentage ownership decreases. Dilution becomes a problem when a company raises at a flat or lower valuation (a down round), or when excessive share issuance erodes your stake without corresponding value creation.
Not necessarily. You still own the same number of shares after dilution. The question is what those shares are worth. If the company's per-share value increased because of a strong funding round, your shares may be worth more in dollar terms even though your percentage ownership is smaller. You lose money only if the total value of your shares goes down, which happens when dilution is combined with a flat or declining valuation.
No. Issuing new shares is a standard corporate action. Companies routinely issue new equity to raise capital, compensate employees, or complete acquisitions. The company's board of directors typically approves share issuances, and existing shareholders may have certain rights (such as preemptive rights or anti-dilution protections) depending on their shareholder agreement. Dilution itself is legal and expected at venture-backed startups.
Dilution reduces your ownership percentage, but it does not change the number of options or shares you hold. For stock options specifically, the key factors are your strike price (the price you pay to exercise), the current fair market value per share (often tied to the 409A valuation), and the total number of fully diluted shares. If dilution is paired with valuation growth, the spread between your strike price and the current share price can still widen, making your options more valuable. The risk is when dilution happens without meaningful valuation increases, shrinking both your percentage and the potential upside per share.
The information provided is not professional advice and is not intended by Secfi, Inc., its affiliates, and Secfi representatives, to be deemed as investment, legal, tax or other professional advice or recommendations of any kind, or to form the basis of any decision to do or to refrain from doing anything.