Fully Diluted Shares Explained With a Worked Example

You own half the shares, so you own half the company. Right? Not quite. Once options, warrants and SAFEs enter the picture, the number that investors, lawyers and acquirers care about is your fully diluted ownership. This guide explains what goes into that number and walks through one simple example from start to finish, so you can check your own math with confidence.

The end of December is a quiet week for many founders, and it is a good moment to open the cap table and actually understand it. If you are planning to raise in the new year, hiring with equity, or simply wondering what your stake is worth on paper, fully diluted shares are the number to get comfortable with.

The concept sounds technical, but it comes down to one question: if every promise of future shares turned into real shares today, how many shares would exist, and what slice would each person hold? Let's take it apart piece by piece.

A quick note before we start: this is general information to help you follow the math, not legal, tax or investment advice. Your company's documents and your lawyer have the final word on how any instrument converts.

What "fully diluted" actually means

There are two common ways to count a company's shares, and they answer different questions.

Issued and outstanding shares are shares that actually exist and sit in someone's name today. Founders' common stock, shares bought by early investors in a priced round, and shares from options that employees have already exercised all belong here. These are the shares that can vote right now.

Fully diluted shares take that number and add everything that could become shares later. The usual list is:

• Issued shares: common and preferred stock already held by founders, employees and investors.
• Granted options: stock options promised to employees, advisors or contractors, whether vested or not.
• The unissued option pool: shares set aside for future grants that have not been handed out yet.
• Warrants: rights to buy shares, often given to lenders or partners.
• Convertible instruments: SAFEs and convertible notes, counted on an as-converted basis, meaning you estimate how many shares they would turn into.

The fully diluted view is the "worst case" for anyone's percentage, because it assumes every possible share is out in the world. That is exactly why investors prefer it. When they buy 15% of your company, they want 15% after everything that has been promised, not 15% of a number that will quietly grow later.

Why the unissued pool counts

Including shares that no one owns yet feels odd at first. The logic is simple: the pool exists to be granted, and once it is granted, it dilutes everyone. Counting it now means no one is surprised later. This is also the root of the option pool shuffle, where a new or bigger pool is counted in the pre-money valuation so its dilution falls on existing holders, mostly founders. We will not go deep on that here, but it is a direct consequence of how the fully diluted count is defined.

Why the number matters to founders

It is tempting to treat this as a lawyer's problem. In practice, the fully diluted count shows up in at least four decisions you will make yourself.

• Pricing a round. In a priced round, the price per share is usually the pre-money valuation divided by the fully diluted pre-money share count. A bigger count means a lower price per share for the same valuation.
• Making option grants. When you offer a new hire "0.5% of the company," you need to know 0.5% of which number. Using the fully diluted count avoids promising more than you meant to.
• Reading SAFEs. A post-money SAFE gives the investor roughly the investment divided by the post-money cap. That percentage is measured against a defined capitalization, which is close to a fully diluted count.
• Talking to acquirers. In a sale, the price is split across the shares that exist once options and convertibles are dealt with. Knowing your fully diluted stake tells you what you would actually receive.

A worked example, step by step

Let's build a fully diluted count for a made-up startup called Brightline. Every number below is invented for illustration only. Your own documents will have their own definitions, so treat this as a way to understand the logic, not as a formula to paste into a term sheet.

Brightline's starting position

• Two founders each hold 4,000,000 shares of common stock (8,000,000 issued shares in total).
• Employees and an advisor have been granted options over 600,000 shares. Some are vested and some are not; all count.
• The option pool has another 400,000 shares reserved but not yet granted.
• A lender holds a warrant to buy 50,000 shares.
• An angel invested $500,000 (example amount) on a post-money SAFE with a $10 million valuation cap (example amount).

1. Start with issued shares. Brightline has 8,000,000 issued shares. On this basis each founder owns exactly 50%.
2. Add granted options. 8,000,000 plus 600,000 equals 8,600,000.
3. Add the unissued pool. 8,600,000 plus 400,000 equals 9,000,000.
4. Add warrants. 9,000,000 plus 50,000 equals 9,050,000. This is the fully diluted count before the SAFE.
5. Estimate the SAFE on an as-converted basis. With a post-money cap, the angel's ownership is roughly the investment divided by the post-money cap: $500,000 divided by $10,000,000 equals 5%. The SAFE shares need to be 5% of the new total, so you solve for them: 5% of (9,050,000 plus SAFE shares) equals the SAFE shares. That works out to about 476,316 shares.
6. Add it all up. 9,050,000 plus 476,316 equals 9,526,316 fully diluted shares.
7. Calculate each percentage. Divide each holder's shares (or potential shares) by 9,526,316.

The result: two views of the same company

Here is how Brightline looks on both bases. Notice how the founders' slice changes even though nobody sold or gave away a single share.

(Figures are rounded, so the percentages may not add up to exactly 100.00.) Each founder goes from 50% of the issued shares to just under 42% fully diluted. That gap is not a loss. It is the honest picture of commitments the company has already made.

A note on SAFE math in real life

The neat "5% of the new total" calculation is an approximation. Real SAFEs define exactly which shares are included in the company capitalization, and the conversion happens at the next priced round, when the round's own new pool and the other SAFEs all enter the calculation at once. If a SAFE has both a cap and a discount, the investor usually gets whichever gives the lower price. With a discount, the conversion price is the round price times (1 minus the discount). When you have several SAFEs with different caps, the cleanest approach is a cap table tool or a model your lawyer checks, rather than mental math.

What usually goes in, and what sometimes does not

Most of the time the list above is the whole story. There are a few gray areas worth knowing about, because they are where negotiations happen.

Items that are almost always included

• All common and preferred shares already issued.
• All granted options and restricted stock, vested or unvested.
• Warrants, unless they have expired.
• The existing unissued option pool.

Items that are negotiated or depend on the documents

• A new or increased pool for the upcoming round. Whether this sits in the pre-money count is the classic negotiation point, because it decides who bears the dilution.
• SAFEs and convertible notes that convert in the round. Some term sheets include them in the pre-money count, some calculate them separately. The choice shifts dilution between founders and new investors.
• Accrued interest on convertible notes. If interest converts into shares too, it adds to the count. Check the note.
• Promised but undocumented grants. If you told someone, even in an email, that they would get options and never papered it, an investor will likely want it counted, and fixed, before closing.

How to calculate your own fully diluted count

You do not need special software to get a first answer. A spreadsheet and an hour of focus will do. Here is a template you can copy.

Fully diluted cap table template

The example rows use made-up numbers. Add one row per holder, plus a row for the unissued pool, and keep a total at the bottom that every percentage divides by.

1. Gather your documents. Stock purchase agreements, option grant notices, the equity plan, warrant agreements, every SAFE and every convertible note.
2. List every holder. One row each, including people whose options are unvested.
3. Fill in the issued shares. Only shares that exist today.
4. Add options and warrants. The number of shares each one could become.
5. Estimate the convertibles. Use each SAFE's or note's terms and label the result as an estimate.
6. Add the unissued pool. Take the total pool size from your equity plan and subtract what has been granted.
7. Check the totals. Your fully diluted total should match the sum of all rows, and your issued total should match the share register.

Frequently asked questions

The bottom line

Fully diluted shares are simply the count of everything that exists plus everything you have promised. Once you add options, the pool, warrants and convertibles to your issued shares, you get the number investors use to price rounds and the most honest view of who owns what.

Spend a quiet hour this week building both views in a spreadsheet, label your estimates clearly and have a professional check the result. You will walk into next year's conversations knowing your real numbers, and that confidence is worth a lot more than a rounded-up percentage.