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Free tool
Model up to 3 stacked post-money SAFEs converting at a priced Series A, with an option pool refresh, and see your final founder ownership at close. Each SAFE row + the entire Series A encodes into the URL — share the exact scenario with your co-founder, board, or lawyer without retyping a number.
It models the cap-table outcome when you raise multiple post-money SAFEs and then a priced Series A with an option pool refresh. Each SAFE converts at its own post-money cap, the Series A investor takes their priced percentage, the option pool is sized to the target post-round, and the residual is your founder ownership at close.
Most early-stage companies raise 2-3 SAFEs before a priced round; 3 slots covers the realistic range. If you have more, sum smaller SAFEs that share a cap into a single row (the math is identical), or open the calculator multiple times to compare scenarios. A future v2 may extend to N SAFEs.
v1 assumes each SAFE converts at its post-money cap (the cap-binding case). It does not model discount conversion. For cap-vs-discount math on a single SAFE, use the dedicated /tools/safe-calculator — it shows when the cap binds, when the discount binds, and the resulting effective valuation.
v1 sets the option pool as a target percentage of the post-round cap table and dilutes everyone proportionally — founders, SAFE holders, and Series A investors. The YC standard 'option pool comes out of pre-money' is an approximation that requires an iterative SAFE-and-pool waterfall; v1 simplifies for legibility. The difference is meaningful at large pool refreshes (>15%) and should be confirmed with your lawyer.
When SAFE ownership + Series A percentage + option pool sum to more than 100% of the post-round cap table, the founders' residual is negative — mathematically impossible in a real cap table. This usually means the SAFE caps are too low relative to the Series A pre-money, the SAFE amounts are too large for the caps, or the option pool target is too aggressive. The calculator flags this with a red band so you can adjust inputs.
Yes — every SAFE row + the entire Series A is encoded in the URL. The 'Copy share link' button copies the current URL to your clipboard. Send it to your co-founder, board, or lawyer and they open the calculator with the same numbers ready to inspect.
Single-SAFE math
Cap vs discount conversion for one SAFE. Pair with this stack calculator when you need to know which mode binds.
Definition
The canonical definition with cross-references to the rest of the venture vocabulary.
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Up to 3 stacked post-money SAFEs. Each converts at its own cap. Leave unused rows at 0.
The priced round all SAFEs convert into. Option pool refresh target is taken from the post-round cap table.
Founders' final ownership
50.00%
Excellent — founders retain 50.00% after Series A.
v1 assumptions: each SAFE converts at its post-money cap (cap-binding). Discount handling omitted — for cap-vs-discount math on a single SAFE see the dedicated SAFE calculator. Option pool dilutes the pre-Series-A cap table evenly. Real pre-money pool refresh is iterative — use this for back-of-envelope, confirm with your lawyer or finance lead before signing term sheets.
Reading the bands: ≥50% founders is exceptional retention. 30-50% is the typical post-Series-A target. 15-30% is dilution-heavy. Below 15% leaves little room for Series B+ dilution. Negative means the inputs imply over-allocation — check that SAFE caps + Series A + option pool don't sum past 100%.
The URL contains every SAFE row + the Series A — drop into a board deck or co-founder conversation without retyping.
Educational tool. Real dilution math depends on the precise SAFE documents (post-money vs pre-money, MFN, pro-rata, side letters), the actual option pool waterfall, and any anti-dilution provisions. Not legal or tax advice — talk to your lawyer.