Pre-money vs post-money valuation, with the arithmetic shown

Pre-money valuation is what a company is agreed to be worth before new investment arrives. Post-money valuation is the same company's value immediately afterwards. The two differ by exactly the amount of money going in: post-money valuation equals pre-money valuation plus the new investment, and the new investor's percentage stake equals their investment divided by the post-money figure. That arithmetic takes thirty seconds to learn, and it still catches experienced people out, because two deals that quote an identical pre-money number can hand the new investor very different stakes once an option pool, a SAFE or a convertible note is added to the picture.

The formula, and what it buys the investor

The core relationship has three parts, and each one is fixed once the other two are agreed.

The numbers above are an illustration built for this article, not a real transaction. The investor's stake is always calculated against the post-money figure, not the pre-money one, which is why a founder who hears "we're valuing you at £8 million" should immediately ask whether that is the pre-money or the post-money number. The same £2 million cheque against a £8 million post-money valuation would buy 25%, not 20%, because the pre-money figure would then be only £6 million.

This is also why the same headline valuation is not automatically the same deal. A company agreeing £8 million pre-money with a straightforward priced round, no pool top-up, no earlier SAFEs converting, ends up in a genuinely different place from one agreeing the same £8 million pre-money once those other instruments are accounted for. The rest of this article is about where that difference comes from.

Where the simple formula breaks down: the option pool shuffle

Most funding rounds include an option pool, a block of shares set aside to grant to future employees. The question that changes everything is timing: is the pool created before the new investment (inside the pre-money figure) or after it (inside the post-money figure)?

When an investor asks for the pool to sit in the pre-money valuation, as is standard practice in many venture rounds, the pool dilutes the existing shareholders, mostly the founders, but not the incoming investor, whose post-money percentage is the number actually fixed in the term sheet. HSBC Innovation Banking's explanation of employee option pools describes the result plainly: founders are diluted twice, once by the investment itself and again by the pool's creation.

These figures are illustrative. The point to notice is that the investor's 20% does not move between the two columns. The entire cost of the pool lands on the existing shareholders, because the pool is issued before the investor's money arrives and the investor's target percentage is calculated after it. A pool sized to the actual hiring plan, rather than to a round number an investor proposes, and modelled against the post-round cap table before signing, is the usual way to avoid giving away more than intended. Our guide to what is a term sheet covers the clause this usually appears in and what else to check in the same document.

SAFEs and convertible notes complicate it further

A SAFE (a simple agreement for future equity) or a convertible note defers the valuation decision rather than setting a share price immediately. Both can still carry a valuation cap, a ceiling on the price at which they convert into shares, and that cap can be written on a pre-money or a post-money basis.

Y Combinator, which introduced the SAFE and moved to a post-money version as its standard form in 2018, explains the distinction directly: a post-money valuation cap is the valuation of the company after the investment is made, so the ownership being sold is simply the investment divided by that cap. A $500,000 investment against a $6,700,000 post-money cap sells roughly 7.5% immediately, with little further arithmetic needed. A pre-money cap cannot offer that certainty, because the final ownership also depends on any other SAFEs outstanding, the size of the option pool, and the terms of whatever priced round eventually converts everything into shares.

The practical consequence: a post-money SAFE tells an investor and a founder roughly what they will each hold once the instrument converts. A pre-money SAFE tells them the price, but not the final percentage, until the rest of the capitalisation table is known. Neither is wrong, but a founder stacking several SAFEs from different investors needs to know which kind each one is before promising anyone a number.

UK early-stage deals use a close equivalent, the advance subscription agreement, built as a genuine prepayment for shares rather than a US-style convertible instrument, partly because that structure sits more comfortably with SEIS and EIS conditions. Whether a given SAFE or advance subscription agreement actually qualifies for UK tax relief is a separate, fact-specific question; our plain-English guide to SEIS and EIS sets out the current conditions, and tax rules change, so check current HMRC guidance before relying on either.

Why the same headline number can still mean different things

Put the pieces together and a stated pre-money valuation on its own answers less than it appears to. Two companies can agree an identical £8 million pre-money figure and end up with founders holding noticeably different percentages, depending on whether a pool sits inside or outside that number, whether earlier SAFEs convert before or alongside the new money, and what else the term sheet attaches to the price, such as a liquidation preference that decides who gets paid first on a sale. None of that shows up in the single headline number that gets repeated in conversation.

This is not a reason to distrust valuation as a concept. It is a reason to always ask for the fully diluted post-money cap table, the actual list of who holds what percentage after every instrument has converted and the pool has been created, rather than relying on the pre-money figure by itself. Anyone building this vocabulary from scratch will find it covered alongside cap tables, SAFEs and convertible notes in our first-year plan for a new angel investor; the Republic of Investors community is a reasonable place to ask how a specific structure compares with what others doing similar early-stage deals have seen, before you commit to a number.

What to do next

Before agreeing to or signing anything, ask three questions in order. First, is the valuation being discussed pre-money or post-money, and has anyone said "valuation" without specifying which. Second, where does the option pool sit, inside the pre-money figure or added on top of it, and is its size justified by an actual hiring plan rather than a habit. Third, if a SAFE or convertible note is involved, is its cap pre-money or post-money, and what else is already outstanding that will also convert. Answering those three turns a single quoted number into an actual percentage ownership you can check against the cap table, which is the number that matters.

Common questions

Is pre-money or post-money valuation the "real" value of the company? Neither is more real than the other; they describe the same negotiated figure at two different moments, before and after the new money arrives. Confusion happens when a number is quoted as "valuation" without saying which one is meant, so always ask.

Does a higher pre-money valuation always mean a better deal for a founder? Not by itself. A high pre-money figure attached to a large pre-money option pool, a participating liquidation preference, or several converting SAFEs can leave a founder with a lower final percentage than a lower headline valuation with cleaner terms. The post-money cap table, not the headline number, decides that.

What is the option pool shuffle? It is the common practice of creating or topping up the employee option pool inside the pre-money valuation, so the pool dilutes existing shareholders but not the incoming investor. It is legal and widespread, but worth negotiating on pool size rather than accepting the first number proposed.

Do pre-money and post-money SAFEs convert to the same number of shares? Not necessarily. A post-money SAFE fixes the investor's percentage of the company as it stands at signing, including other SAFE money, which makes the outcome more predictable. A pre-money SAFE's final percentage depends on what else exists at conversion, including the option pool and any priced round terms, so it can land differently even from an identical-looking cap.

Is the UK advance subscription agreement the same as a US SAFE? They do a similar commercial job, letting an investor pay now against a value set later, but they are structured differently in law: an advance subscription agreement is built as a prepayment for shares rather than a convertible instrument. Whether either qualifies for SEIS or EIS relief depends on the specific terms and current HMRC guidance.