safe-stack-conversion

Convert a stack of YC SAFEs (post-money and pre-money) and convertible notes into a pro-forma cap table at a priced round. Fixed-point solve, cap/discount best-price-wins, interest accrual. Zero dependencies.

npm install safe-stack-conversion

Why

Every seed-stage company carries a stack of SAFEs, and "what does the cap table look like after the Series A?" is a genuinely fiddly computation: post-money SAFEs pin ownership (amount ÷ cap), discount instruments convert at a price that depends on the round PPS, and the round PPS itself depends on how many shares the stack converts into. It's a simultaneous system — this package solves it by fixed-point iteration and preserves the YC identities exactly.

import { convertStack } from "safe-stack-conversion";

const pf = convertStack(
  [
    { name: "SAFE-1", kind: "safe-post-money", amount: 1_000_000, cap: 10_000_000 },
    { name: "SAFE-2", kind: "safe-pre-money", amount: 500_000, cap: 8_000_000, discount: 0.2 },
    { name: "Note-1", kind: "note", amount: 250_000, interestRate: 0.06, years: 1.5, discount: 0.2 },
  ],
  { preMoney: 20_000_000, investment: 5_000_000, preRoundFullyDiluted: 10_000_000 },
);

pf.instruments[0].ownership;      // SAFE-1's post-round stake
pf.instruments[0].basis;          // "cap" | "discount" | "price" — which term won
pf.pricePerShare;                 // preMoney / company capitalization (incl. SAFE shares)
pf.ownership;                     // { existing, safesAndNotes, newInvestor } — sums to 1

Semantics (documented, matching the YC post-money SAFE)

• Post-money SAFE with cap: converts at cap / companyCapitalization — so its ownership of the company capitalization is exactly amount / cap, the YC headline number (verified in tests).
• Pre-money SAFE / note with cap: converts at cap / preRoundFullyDiluted.
• Discount: converts at (1 − d) × round PPS. Cap + discount → whichever price is lower wins (basis reports which).
• Notes: principal accrues simple (default) or annually-compounded interest to the conversion date.
• Company capitalization = pre-round fully diluted + all converting shares, excluding new money and new pool top-ups; round PPS = preMoney / capitalization, solved simultaneously with the stack.

Also exported: postMoneySafeOwnership(amount, cap) — the one-liner identity.

Related

Part of a cap-table math family: priced-round-math (option-pool shuffle) · exit-waterfall · vesting-schedule-math.

Author

Built by Moshe Malka — engineering leader in New York City. Studio work at Quentin.Code.

MIT © Moshe Malka