Price Per Share Formula: How to Calculate It

The price per share in a venture financing is the per-unit cost the new investors pay for newly-issued preferred stock. It’s the number that determines exactly how many shares the round produces, and it’s the anchor point for every downstream calculation in the cap table: option pool sizing, founder dilution, conversion ratios, and exit waterfall outcomes.

The formula looks trivial: pre-money valuation divided by fully-diluted shares. The trap is the denominator. Get the share count wrong by even a small margin and the per-share price moves enough to materially shift founder ownership at closing.

Definition: Price per share is the per-unit purchase price for newly-issued shares in a financing round, calculated as the company’s pre-money valuation divided by the fully-diluted share count immediately before the round closes.

The formula

Price per share = Pre-money valuation / Fully-diluted pre-money shares

Three terms, each with a specific meaning:

• Pre-money valuation. What the company is “worth” immediately before the new money is invested. Negotiated with investors, set in the term sheet.
• Fully-diluted shares. The total share count assuming every option is exercised, every warrant is converted, every convertible security has converted, and the unallocated option pool is fully issued.
• Pre-money. Both quantities are measured before the new round closes. The new investors’ shares aren’t in the share count and the new money isn’t in the valuation.

The output is a per-share price the new round pays. New investors then receive (their investment / price per share) shares of preferred stock.

Worked example: Series A close

Company before the round:

• 8,000,000 founder common shares outstanding
• 1,000,000 employee options issued and outstanding
• 500,000 unallocated option-pool shares
• 500,000 SAFE shares (post-money cap conversion modeled)

Round terms:

• $5,000,000 raise
• $20,000,000 pre-money valuation
• Option pool to be expanded to 15% post-money

Step 1: calculate pre-money fully-diluted shares. This is where teams get tangled up. The investor demands the option pool be sized so that the pool sits at 15% of the post-money fully-diluted share count, and that the cost of the expansion comes out of the founders’ pre-money equity. That requires solving for the new pool size.

For simplicity, assume the share count after pool expansion (still pre-money) is:

Founder common:          8,000,000
Existing options:         1,000,000
Existing unallocated:       500,000
SAFE conversion:            500,000
New pool added:           1,235,294   (solved to put final pool at 15% post-money)
Total pre-money FD:      11,235,294

Step 2: calculate price per share.

$20,000,000 / 11,235,294 = $1.7800/share

Step 3: calculate new investor shares.

$5,000,000 / $1.7800 = 2,808,989 shares

Step 4: verify post-money totals.

Pre-money FD:           11,235,294
New Series A:            2,808,989
Total post-money FD:    14,044,283

Series A ownership: 2,808,989 / 14,044,283 = 20.00%
Option pool % post-money: (500,000 + 1,235,294) / 14,044,283 = 12.36%

If the option pool target was 15% post-money, the pool sizing was wrong, and that’s exactly the kind of iteration that has to happen in cap table modeling to land at clean closing numbers.

What goes in the fully-diluted share count

Five share categories typically count:

1. Outstanding common stock. Founder shares, employee shares already issued and exercised.
2. Outstanding preferred stock, on an as-converted basis. Existing Series Seed or Series A preferred convert to common at their conversion ratio (usually 1:1).
3. Issued and unexercised options. Vested or unvested, exercised or not: they count.
4. Unallocated option pool. All shares authorized in the option plan that haven’t been granted yet.
5. Convertible securities. SAFEs, convertible notes, warrants, converted at the price they would convert to in this round (the cap, the discount, or the round price, whichever applies).

The most common error: forgetting to fully-convert SAFEs and convertible notes. A SAFE with a $5M cap converting at a $20M priced round produces 4× the shares of a same-dollar new investor, and those shares need to be in the pre-money fully-diluted count, not added afterward.

Pre-money vs post-money mechanics

The pre-money vs post-money distinction is the source of more cap table arguments than any other concept.

• Pre-money valuation is what the company is worth before the new money. Used in the price-per-share formula to determine investor share count.
• Post-money valuation is pre-money + the new investment. Used to express the round in headline form (“they raised at a $25M post-money”).
• The two are connected: post-money = pre-money + new investment, always.

Where the two diverge in real life is in the fully-diluted share count assumption. Pre-money SAFEs count their conversion shares in the post-money count (after the round). Post-money SAFEs count their conversion shares in the pre-money count, before the new round prices. The latter is what Y Combinator standardized in 2018, and it’s what most modern post-money SAFEs assume.

Common mistakes in price-per-share calculations

Five errors show up over and over:

• Excluding the option pool expansion from pre-money. If the round requires an expanded pool and the term sheet says “pre-money pool expansion,” the new shares need to be added to the pre-money fully-diluted count. Forgetting this is the #1 cause of post-close founder dilution surprises.
• Modeling SAFEs at the wrong conversion price. A SAFE with a cap and discount converts at whichever produces more shares, not whichever the founder prefers. Use the lower per-share price. (An uncapped SAFE has no cap, so it converts on the discount alone.)
• Forgetting to count un-issued option pool. Authorized but unallocated pool shares are still part of fully-diluted. Excluding them inflates the price per share and gives the new investor fewer shares than they should get.
• Mixing pre-money and post-money inputs. Always work consistently: either both in pre-money terms (price formula uses pre-money valuation, pre-money FD shares) or both in post-money. Mixing produces nonsense.
• Rounding the price too early. Price per share to four decimal places is normal. Rounding to two decimals before computing investor share count causes a small but real mismatch in post-close ownership.

Frequently asked questions

What’s the difference between price per share and conversion price?

Price per share is what new investors pay in a financing round. Conversion price is the per-share price at which a convertible security (SAFE, note, preferred stock) converts into common at a future event. They can be very different: a SAFE with a $5M cap converting in a round priced at $20M will have a conversion price 4× lower than the round’s price per share.

How is price per share calculated for a SAFE conversion?

Take the lower of (cap / fully-diluted shares) and (round price × (1 - discount)). The cap path uses the SAFE’s pre-agreed cap valuation; the discount path uses a percentage off the round’s price per share. The SAFE holder gets whichever produces more shares.

Does price per share change after closing?

The original Series A price per share doesn’t: it’s fixed in the certificate of incorporation. But future rounds price differently, and anti-dilution adjustments to existing preferred shares can change the effective price (via conversion ratio changes) of older series.

What’s a “fair” price per share?

There’s no fair number in absolute terms: it’s the output of a negotiation over pre-money valuation. What matters is whether the resulting ownership split is acceptable to founders and aligned with comparable companies in the same stage.

Why doesn’t the post-money valuation equal new investor shares × price per share?

Because the post-money valuation includes the value of all the company’s shares, not just the new ones. Post-money valuation = (post-money fully-diluted shares × price per share). The new round’s shares are a slice of that.

How does a 409A valuation relate to price per share?

A 409A valuation sets the fair market value of common stock for tax purposes (typically much lower than the preferred’s price per share). It governs option strike prices, not financing-round pricing. The two numbers serve completely different purposes and shouldn’t be conflated.

What if the cap table has multiple share classes, which price applies?

Each new financing round has its own price per share. Existing share classes keep their original issue prices (until conversion or anti-dilution adjustments). The fully-diluted share count brings everyone to a common-stock-equivalent basis for the price-per-share formula.