A dilution model runs on four inputs from the documents

The record

Y Combinator's SAFE documents page, retrieved 16 September 2026, defines a valuation cap as the highest valuation at which a SAFE converts into shares, and a discount as pricing that lets an earlier investor convert below subsequent equity round valuations, for example on a 20% discount SAFE. Its accompanying Post-Money Safe User Guide sets out how a post-money cap treats a company's option pool: it includes shares already issued or promised, and the unissued and available portion of the option pool that exists before the priced round, but excludes any increase to that pool adopted in the priced round itself. The NVCA Model Certificate of Incorporation, updated October 2025, is the document that later fixes each series of preferred stock's liquidation preference as a stated multiple of its Original Issue Price.

What the sources establish

Together the two organisations' documents show that cap, discount, pool and preference are not modelling choices; they are contract terms defined in specific instruments. A SAFE's cap and discount are set in the SAFE itself, at the time it is signed, and the YC guide explains why the post-money structure was built the way it was: a seed investor's ownership, once capped, should not be diluted by hires made between the SAFE and the priced round, but is expected to share the dilution from a newly enlarged pool adopted at that round. A preference, by contrast, is not a SAFE term at all; it is set later, in the Certificate of Incorporation negotiated at the priced round, as a multiple applied to the price paid per share.

Scope and revision

No calculator is claimed here, only the inputs one needs. A spreadsheet modelling dilution across a SAFE-to-priced-round sequence has to pull the cap and discount from the SAFE, the size of the pre-existing and promised option pool from the company's own cap table, any pool increase from the term sheet for the priced round, and the liquidation preference multiple from the Certificate of Incorporation, since the NVCA model leaves that multiple as a blank to be negotiated rather than a fixed default. A model that hardcodes a standard preference, or ignores the promised-but-ungranted options the YC guide describes, will not match either document.

The decision in front of you

This is an editorial method for gathering inputs, not a substitute for legal review of the actual signed documents. Before modelling dilution across a raise, pull the four terms from the instruments that define them rather than from memory of a typical deal.

• What valuation cap and discount, if any, does the SAFE itself state?
• Does the option pool figure used include promised-but-unissued options, and does it exclude a pool increase adopted at the priced round?
• What liquidation preference multiple did the negotiated Certificate of Incorporation set, as opposed to the NVCA template's blank?

The documents, not the spreadsheet, decide what each input is. The spreadsheet only decides how the inputs combine.