Building numero.sh#

numero.shnumero.sh is napkin math done right: a shareable, text-based calculator.

Instead of filling tiny formula boxes in a spreadcaptursheet, you write calculations as plain text:

seats = 120
monthly = seats * 39
monthly * 12

Results appear line-by-line, right next to your math. Every sheet can be encoded directly in the URL, which means sharing is as simple as copying the address bar.

Why I built this#

I kept running into the same friction: I wanted the speed of a calculator, the structure of a spreadsheet, and the clarity of writing things down in plain language.

• Calculators are fast, but the context disappears after each step.
• Spreadsheets are powerful, but often too heavy when I only need a lightweight scratchpad.
• Notes are flexible, but they do not evaluate anything.
• Sheets are complex, not everyone knows how to use them, and I wanted a web application that was easy to embed anywhere (namely Notion, see below)

numero.sh sits in the middle. I wanted a place where I could think in equations, keep intermediate variables, and still share the exact state of my work in one link.

There are many alternatives out there that sort of worked, but none that met all my requirements.

The motivation behind the product decisions#

The project is built around a few strong bets:

• Text first: math should feel like writing, not configuring cells.
• Share/embed by default: the URL is the document, so collaboration starts with copy/paste.
• Optional persistence: local scratch mode for quick work, GitHub sync when you want durable storage.
• Keyboard-driven flow: command palette and shortcuts keep the interaction fast.
• Readable output: per-line results and formatting controls keep calculations understandable. I did not want another all-in-one finance tool. I wanted a focused shell for everyday numeric thinking: pricing ideas, quick planning, sanity checks, and back-of-the-envelope models.

What led me here#

numero.sh came from repeated personal use cases:

1. Doing quick business math that grows from 2 lines into 40.
2. Sharing those calculations with someone else without screenshots.
3. Reopening the same logic later and understanding it immediately. Over time, that turned into a clear direction: build a small, reliable math workspace that is easy to start, easy to share, and hard to outgrow for simple modeling.

The result is numero.sh: a calculator you can read, edit, and send like a note.