What did you actually sell?
SAFEs get signed one at a time, months apart, each feeling small. They convert on the same day — this is that day.
The instruments
The pre/post choice is per document, not per round. Mixed stacks are normal and the difference is the point.
| Name | Amount | Valuation cap | Discount % | Kind | |
|---|---|---|---|---|---|
A model from the terms you enter, not legal or investment advice. Read your own documents; a term this does not ask about can change the answer.
They are signed one at a time and they convert all at once
The trouble with SAFEs is not that any one of them is hard to understand. It is that they are negotiated alone, months apart, in the middle of doing something else. Each one feels proportionate. Nobody models the stack, because until the priced round there is nothing to model it against, and by the time there is, the terms are fixed and the conversation is about something else entirely.
The mechanic that does most of the damage is also the one presented as an improvement. A post-money SAFE tells the investor precisely what share they are buying on the day they sign — a real advance on the pre-money version, which left both sides guessing until the round closed. But fixing a percentage against the post-conversion total has a second effect that is rarely spelled out: it makes that percentage immune to every SAFE signed afterwards. The later investor cannot dilute the earlier one. The dilution still happens; it is simply routed around them and onto the founders.
Run three of them and the arithmetic is unforgiving. Three separate $500,000 cheques at a $5m cap are thirty percent of the company, and not one of those conversations would have felt like selling thirty percent. Run the same money on pre-money paper and the investors share the dilution with you. Neither structure is dishonest. The difference is worth several points of your company, and it is decided by which template someone attached to an email.
The option pool is the same kind of quiet term. Carved out of the pre-money, it is funded by the founders and the existing holders while the incoming investor’s percentage stays exactly where the term sheet says. It is discussed, when it is discussed at all, as a definitional detail. Model it both ways, and the investor’s own line on the cap table moves — which is the version of the argument worth having with them.
What this tool does not do
It models cap, discount, pre/post and the pool, which is what decides the answer in most stacks - and nothing else. Real documents carry terms this does not ask about, and any one of them can move the number: MFN clauses, pro-rata rights, side letters, liquidation preferences, participation, and how the SAFE's own definition of company capitalisation treats unissued option shares. It treats founders and existing holders as one block, and assumes every instrument converts in the same round at the same time.
- Reading your actual documents - a term not in the four fields above can change the result
- MFN clauses, side letters, pro-rata rights or anti-dilution protection
- Liquidation preferences and participation, which decide who gets what in an exit and are usually more consequential than the percentages here
- Splitting the founders from each other, or modelling vesting, leavers or founder share forfeiture
- Whether the valuation cap you agreed was a good one
- Tax on anything - grants, conversions, exits, or where you live
- Your lawyer, whose job this is and who will read the document rather than four numbers from it
Frequently asked questions
What is the difference between a pre-money and a post-money SAFE?
A post-money SAFE fixes the investor's percentage of the company measured after every convertible has converted — invest $1m at a $6.7m cap and you own about 15%, known on the day you sign. A pre-money SAFE converts at a price rather than to a percentage. The consequence is that post-money holders are protected from every SAFE signed after them, and pre-money holders are not.
So do two post-money SAFEs dilute each other?
No, and that is the single most expensive thing founders learn late. Because each holder's percentage is fixed against the post-conversion total, a later SAFE cannot reduce an earlier one. The dilution has to land somewhere, and it lands entirely on the founders. Three $500k SAFEs at a $5m cap are 30% of the company between them, and every point of it comes out of your side.
Is the post-money SAFE a worse deal then?
It is a clearer one, which is not the same question. The pre-money version left investors genuinely unable to calculate what they had bought until the round closed, and Y Combinator changed it for good reasons. The problem is not the document, it is that founders read "transparent and calculable" as a benefit to them and then sign four of them without ever adding up the total.
Why does the option pool matter so much?
Because of where it is carved from. A pool created as part of the round is almost always taken out of the pre-money valuation, which means it dilutes the founders and existing holders while leaving the incoming investor's percentage untouched. It is presented as a mechanical definition rather than a term, it is negotiable, and it frequently costs more than the terms that get argued over for a week.
Does falling below 50% mean I have lost control?
Not by itself, and treating it that way is a distraction. Control lives in board composition, consent rights and protective provisions, not in a percentage. A founder with 55% and three investor consent rights over every meaningful decision has less control than one with 40% and a friendly board. What crossing 50% does mean is that those documents stop being boilerplate — which is a reason to read them before the round, not after.