Founders & Small BusinessFree
SAFE and Note Conversion Calculator
Send every SAFE and note you signed, plus your cap table, and get one converted cap table showing what each instrument actually cost you per point.
River reads every SAFE and convertible note you have actually signed, then converts all of them at once against a priced round you name. What comes back is a cap table rather than an explanation. In the worked example a company raised $2.9 million across five instruments over 26 months, and those five committed 35.9% of the company before the priced round opened at all. The founders had read the same five documents and would have told you they had sold roughly twenty.
The arithmetic is not hard, it is just never done together. A post-money SAFE fixes its holder's percentage at the investment divided by the cap. Y Combinator, which wrote the instrument, works the example in one line: raise $500k at a $5.5M cap and $500k at an $8.3M cap and you have sold about 15%. Those percentages add, because none of them dilutes another. Every point of the stack lands on the founders and the option pool, and no single document shows you the total.
Built for the week the term sheet arrives, and for the month before you decide whether to take a bridge. Read it alongside the term sheet explainer, which handles the clauses this one prices. The output is the input to your next investor update and to the ownership question you will get asked in a board meeting. Founders who have not signed yet usually run it before the customer contract review on the same deal. Every number rests on a share count the cap table cleanup pack settles first.
The cheapest cheque on the table was the most expensive one
The emergency bridge is where this goes wrong. In the worked example the last instrument was $650,000 at a $6 million cap, taken in month 24 when payroll was close. It converted into 7.18% of the company. The lead investor wrote $5,000,000 and got 21.74%. That is $90,551 per point of ownership for the bridge against $230,000 per point for the round, so the money raised in a hurry cost two and a half times what the money raised properly cost.
Then there is the clause nobody models. The first angel's $250,000 was uncapped with an MFN, which YC describes plainly: it "automatically takes the valuation cap or discount of any SAFE you issue later". The bridge was a later SAFE, so a cheque written in month 2 silently re-priced to a $6 million cap agreed in month 24. That election moved 1.97 points from the founders and was worth $385,000 at the round price. YC's own advice is to close the low-cap SAFEs before issuing an uncapped MFN.
Two more things move once the round is real. Cap and discount are not both live: each instrument takes whichever is better for its holder, so the 20% discount on the $12 million SAFE is dead paper above a $15 million post-money and governs below it. And the 35.9% the instruments locked is not what they end up with, because as the user guide puts it, "the safes are like their own round" and get diluted by the Series A. Here that is 35.9% before, 23.8% after.
How it works
Send the paper
Every signed SAFE, note and side letter. Scans are fine. Say which ones were wired and when.
Add today's cap table
Founder shares, options granted, whatever is left unissued in the pool. A rough split is enough to start.
Name a round
The term sheet in front of you, or a range. Include the pool the investor is asking for post-close.
Read the stack
All instruments convert together, with the per-cheque cost of ownership and the founder split at the end.
What you get
- One cap table with every instrument converted at once, not five separate conversions
- Each instrument's locked percentage, and whether its cap or its discount governs at this round price
- The round price at which each discount flips to beating its own cap
- Cost per point of ownership for every cheque, so the expensive money is named
- MFN and side-letter elections resolved against the instruments that actually trigger them
- The option pool top-up modelled where it lands, in the pre-money, and what that costs founders
- Founder ownership before and after, per founder, across the round scenarios you name
Common questions
Why do the SAFE percentages add up instead of diluting each other?
Because a post-money SAFE fixes its holder's share of the company as it stands immediately before the priced round, and a later SAFE does not reduce it. YC's own guidance works the example: $500k at a $5.5M cap plus $500k at an $8.3M cap is about 15% sold. Nothing absorbs that except the founders and the pool.
Does the cap or the discount apply?
Whichever is better for the holder, decided per instrument at the round price. A 20% discount beats a $12 million cap only below a $15 million post-money, so the same document governs by cap in a good round and by discount in a bad one. The model reports the crossover price for every instrument that has both.
What does an MFN clause actually do to me?
An uncapped MFN SAFE adopts the best cap or discount on any SAFE you issue afterwards. In the worked example a $250,000 cheque from month 2 re-priced to the $6 million cap of an emergency bridge in month 24, which cost the founders 1.97 points. Close your low-cap SAFEs before issuing an uncapped MFN.
Why is the option pool top-up counted against the founders?
Because the investor asks for the pool to exist post-close while the shares are created pre-close, so the pre-money is diluted and the new money is not. In the worked example that is 12% of the company, 2,032,696 shares, granted to nobody yet, and paid for almost entirely by the people already on the cap table.
Can it model a round that has not happened yet?
That is the normal use. Name a range rather than a number and every instrument converts against each point in it, which is how the discount-versus-cap crossovers become visible. Founders deciding whether to take a bridge usually model the round with and without it, because the bridge changes the round it converts into.
What if I cannot find all the paperwork?
Model what you have and the gaps get listed as gaps rather than assumed away. Missing side letters are the common one, and they matter, because pro rata and MFN rights usually live in a side letter rather than in the SAFE. An instrument you cannot produce is also a diligence problem worth knowing about now.
Is this a substitute for a lawyer or a cap table platform?
No. It is the analysis you want before either conversation, so you arrive knowing which questions are expensive. Take the output to counsel to confirm the conversion mechanics in your specific documents, and to your cap table platform to record the result. Neither of them will tell you what the bridge cost you.
SAFE and Note Conversion Calculator
Fill in the form and your workspace opens with the work already underway.