How Seedspace is written and checked

Who writes this

Seedspace is an independent reference site. It is researched and written with AI assistance by an automated publishing system run by the site's owner, and checked against the primary sources named on each page. It is not written by a lawyer, accountant or investment adviser, and nothing on it is legal, tax or investment advice. The site is not affiliated with any investor, accelerator, fund, law firm, platform or government body, and it is not paid by any of them.

Each page shows the date it was last reviewed. On that date, rules and thresholds stated on the page were checked against the official source listed under "Sources". Figures that change often (program deadlines, offering limits, tax-relief limits) say "as of" the date they were checked; check the official page before you rely on them.

Editorial rules

• No invented numbers. A figure is either from a named source with its date, an official threshold checked on the official page, or plainly marked as an illustration ("for example"). Market statistics we could not verify from a public source are described in words, not numbers.
• Worked examples are computed, not typed. Every share count, price and percentage in the instrument and term-sheet pages is produced at build time by the same engine as the calculators, so prose and tools cannot disagree.
• Jurisdiction is stated. Most legal detail on the site is U.S. (Delaware-style corporations, SEC rules). U.K. and EU pages say so. Rules elsewhere differ.
• No promotion. No advertising, affiliate links or sponsored content; no investor, platform or service is recommended; nothing here is an offer of securities. If that ever changes, the privacy page and this page will say so first.
• Our own words. We summarize and explain; we do not reproduce model documents. Y Combinator's SAFE forms are published under a Creative Commons No-Derivatives licence, so we describe them rather than copy them.

Corrections

Found an error, an out-of-date rule or a figure that doesn't match its source? Write to corrections@seedspace.io with the page address and what is wrong. We check every report against the source and correct the page; the page's review date changes when we do.

How the calculators compute

The cap-table engine (/static/engine.js in your browser, with an identical Python twin used to build the pages) follows the conventions of Y Combinator's Post-Money Safe User Guide:

• Price per share = pre-money valuation ÷ pre-money fully diluted shares, where the pre-money count includes converting SAFEs and notes and any option-pool increase (the "option pool shuffle"). Prices are rounded to four decimal places; share counts are rounded down.
• Post-money SAFE: shares = Company Capitalization × (purchase amount ÷ post-money valuation cap). Company Capitalization counts all outstanding shares, granted and promised options, the unissued pool and all converting securities, but not the pool increase made in the priced round.
• Pre-money SAFE: conversion price = pre-money cap ÷ (pre-round fully diluted shares + the new pool increase), excluding other converting securities.
• Convertible note: amount converting = principal + simple interest; conversion price as for a pre-money SAFE. Real notes vary (some define capitalization differently, some compound interest); the calculator states the assumption beside every result.
• Each SAFE or note converts at whichever of its cap price, discount price or the round price gives the most shares, as the standard forms provide.
• Option pool: the increase is solved so the available pool equals the target share of the post-money fully diluted capitalization.
• Acquisition before a priced round: each SAFE receives the greater of its purchase amount or its as-converted proceeds, using the Liquidity Capitalization (which excludes the unissued pool).
• Exit waterfall: preferences are paid by seniority (pari passu within a rank), then the remainder is shared by common, converted preferred and participating preferred (up to any cap). Each non-participating or capped class converts to common if that pays it more, iterated until no class wants to switch. Options are treated as exercised and their exercise price is ignored.

Validation against published examples

On every build, the engine recomputes published worked examples: all of the conversion examples in Appendix II and the Quick Start of Y Combinator's Post-Money Safe User Guide (downloaded from ycombinator.com/documents), and examples of note conversion, the option pool shuffle, liquidation preferences and anti-dilution published by law firms and other practitioners (linked in the table). Every source is cited for its figures only. The same cases are run through the browser engine under Node.js. If any result falls outside the stated tolerance, the build stops and the live site is left unchanged.

57 of 57 published values reproduced; browser engine: 50 of 50 engine cases identical to the Python engine and within tolerance of the published value. Checked 2026-10-31.

"Published" values are copied from the guide; where it rounds an intermediate figure (for example it multiplies by a price already rounded to $0.8901), we compute from unrounded inputs and show the tolerance and the reason. Where a source's arithmetic contains a slip (one example elsewhere prints 468,483 shares where its own inputs give 469,483), we leave that figure out rather than test against it.

Sources and licences

Every page lists the specific documents it relies on. Contains public sector information licensed under the Open Government Licence v3.0.

Known limits

• Real documents vary. Side letters, negotiated definitions and state law can change any result here; your signed documents govern.
• The calculators model one priced round at a time. Multiple closings at different prices, warrants, and options with exercise prices are simplified or left out, and the page says so where it matters.
• Tax consequences (for founders, employees or investors) are outside the calculators.
• U.S. focus: other countries use different instruments (for example ASA in the UK, BSA AIR in France) and different securities rules.