SAFE / Convertible Note Converter
Model how SAFEs and convertible notes convert into equity when a priced round triggers conversion — post-money SAFEs (the YC standard), pre-money SAFEs, and convertible notes that accrue interest. For each instrument it solves the conversion price as the lower of the valuation-cap price and the discount price, then builds the pro-forma post-round cap table and shows founder / existing-holder dilution. Pure client-side math — your term-sheet inputs never leave your device.
Inputs
Pre-round company
Triggering priced round
Instruments — up to 4
Conversion & Pro-Forma Cap Table
Per-Instrument Conversion
Pro-Forma Post-Round Cap Table
The round price is solved on a pre-money fully-diluted basis (including converting pre-money instruments + the option pool, excluding new money), iterated to convergence so post-money SAFE ownership and the pool top-up settle simultaneously.
Methodology — math used in this model
Effective principal — SAFEs convert their face amount. Convertible notes accrue simple interest: principal_eff = amount × (1 + rate × years). That accrued amount is what converts into shares.
Cap price vs discount price (lower wins) — each instrument converts at the lower (more investor-favorable) of two prices. The discount price is round_price × (1 − discount%). The cap price depends on the instrument type. If an instrument is uncapped, only the discount price applies; if it has no discount, only the cap price applies; if it has neither, it converts at the round price.
Pre-money SAFE / convertible note cap — the classic pre-money interpretation: cap_price = cap / existing_pre-round_FD, where the denominator is the existing fully-diluted share count BEFORE any SAFE/note conversion, new money, or pool top-up. Shares = principal_eff / conversion_price.
Post-money SAFE (YC standard) — ownership-based, not price-based. A post-money SAFE is promised ownership% = principal_eff / cap of the post-money capitalization. Shares are solved against the full post-round fully-diluted share count so that shares / post_round_FD = ownership%. When uncapped, the post-money SAFE falls back to discount-only conversion against the round price.
Option-pool shuffle — the target pool % is topped up pre-money (it dilutes existing holders + converting instruments, not the new investor). The top-up shares are sized so ESOP reaches the target % of the post-round fully-diluted total: pool_topup = (target% × non_pool_post_shares − existing_pool) / (1 − target%), clamped ≥ 0. Here we treat the existing pre-round FD as carrying no separate ESOP, so the entire target pool is created as top-up.
Iterative convergence — round price, pool top-up, and post-money SAFE shares are mutually dependent (each references totals the others contribute to). The model loops ~25 times: it recomputes round_price = pre_money / pre-money_pricing_FD (existing FD + pool top-up + converting pre-money SAFE/note shares), recomputes pool top-up and post-money SAFE shares against the latest post-round FD, and repeats until the post-round share count stabilizes (< 0.001 change). New money buys new_money / round_price shares.
What's intentionally omitted — MFN (most-favored-nation) and pro-rata side letters, valuation floors, multiple/tiered caps on a single instrument, qualified-financing thresholds, note maturity / repayment scenarios, and conversion to a separate preferred share class with liquidation-preference stacking. Single cap + single discount per instrument only.
Educational financial-modeling tool — not investment advice and not a substitute for legal or institutional-grade cap-table work. SAFE / note terms vary; confirm conversion mechanics against your actual instruments and counsel. All math runs in your browser; no inputs are sent to a server.