Napkin
Size your software business on a napkin
Plain-English market sizing and unit economics for vibe coders, solo founders and venture builders. No spreadsheets and no jargon.
01 — The business problem
Most early-stage founders skip market sizing because the usual path is a TAM/SAM/SOM spreadsheet plus a unit-economics tab. It takes a day, feels intimidating, and gets abandoned halfway. The result is unscoped bets and numbers that fall apart the moment an investor asks where they came from.
02 — The workflow
- The operator picks one of five software archetypes: Consumer Subscription, B2B Self-Serve SaaS, B2B Seat-Based SaaS, High-Touch SaaS, or Usage-Based / API.
- A plain-English intake replaces finance jargon. Who the buyer is, what they pay, how you would reach them.
- Napkin maps the answers to TAM/SAM/SOM and to LTV, CAC and contribution margin using industry benchmarks. Every default links back to its source.
- Outputs render as clean charts and cards. Every assumption is editable in an Advanced panel so any number can be overridden when the founder has better data.
- Exports go out as PNG charts, a PDF summary, or a CSV of every assumption and output, ready to drop into a pitch deck.
03 — What I built
- Five-archetype guided flow, built end to end.
- Sourced benchmark library, with overrides on every input.
- Three-format export (PNG, PDF, CSV) so the output survives leaving the app.
- Booking CTA into a fully sourced fundraising workbook for founders who need to defend the numbers in front of investors.
04 — Tools used
AI Gateway (GPT-4 class LLMs) · React + Vite · Framer Motion · shadcn/ui
05 — Commercial use case
A productised tool for the long tail of pre-seed founders, indie operators and venture builders sizing several bets at once. It replaces the back-of-the-napkin spreadsheet most founders abandon, and upsells into a paid fundraise-grade workbook engagement.
06 — ROI and adoption
A defensible first-pass sizing in a five-minute session instead of a half-day spreadsheet.
Illustrative assumptions
- Baseline: a founder spends roughly 4 to 6 hours assembling a usable TAM/SAM/SOM and unit-economics view manually, and most never finish it.
- Napkin compresses that to a five-minute guided session, with sourced defaults and editable overrides.
- Adoption assumed at one sizing pass per founder per quarter during early traction, plus one repositioning cycle per fundraise.