Think freely. We’ll do the math.

Type plain lines, get live, checked results. Natural math, variables, percentages, dates, unit and currency conversions, and reusable live answer tokens — local, free, and open source.

Download for macOSbrew install --cask Qulierm/tap/numlexinstall Numlex with Homebrew
Numlex: a plain-text sheet of calculations with a live results column on the right

Why a notepad calculator?

  • Live, checked results — every line evaluates as you type, with results in a side column you can verify line by line.

  • Plain language, no formula syntax — write “15% of 4572” or “June 12 + 45 days” and read the answer — no formula bar, no cells.

  • Variables, units & currencies — assign “apple = 65”, then use “apple × 3” anywhere; convert 250 km to m or $500 to EUR in the same sheet.

  • Local, private, free & open source — sheets stay on your Mac — no account, no sync, no GPS. A native Swift app for macOS 26+, free under MIT and built in the open on GitHub.

See it in action

Real Numlex sheets, exactly as they run on your Mac. Animations play as they enter view and respect your reduced-motion settings.

Variables & Functions

Define a value once and reuse it everywhere — percentages, powers and functions follow, with a live total that updates as you type.

Variables & Functions: Define a value once and reuse it everywhere — percentages, powers and functions follow, with a live total that updates as you type.

Natural Calculations

Plain lines, natural language: section headings, running totals and even date math — no special syntax and no modes to learn.

Natural Calculations: Plain lines, natural language: section headings, running totals and even date math — no special syntax and no modes to learn.

Units & Currencies

Convert units, temperatures and money in the same sentence you’d say it — “250 km to m”, “$500 to EUR” — with the result right on the line.

Units & Currencies: Convert units, temperatures and money in the same sentence you’d say it — “250 km to m”, “$500 to EUR” — with the result right on the line.

Linked Answers

Every result is a reusable number: later lines can reference it directly, so one value stays consistent across the whole sheet.

Linked Answers: Every result is a reusable number: later lines can reference it directly, so one value stays consistent across the whole sheet.

Everything a notepad should do

A native Swift app — SwiftUI over TextKit with a strict pure-Swift parser, no web view and no scripting engine — free under the MIT license. Beyond the live math column, it behaves like the notes app you already reach for.

All features in the README

  • Natural calculations

    Plain lines all the way — sections, percentages and a standalone total line that sums the unitless results above it.

    • 15% of 4572
    • June 12 + 45 days
    • # Shopping list
    • total

  • Variables & functions

    Assign once, reuse anywhere. Built-ins evaluate live, arguments included.

    • apple = 65
    • apple × 3
    • sqrt
    • sin(radians(30))
    • pow

  • Unit conversions

    Length, area, volume, mass, time, speed, temperature and more — in the same sentence you’d say it.

    232 base unit definitions

    • 250 km to m
    • 34 C to F

  • Currencies, live rates

    ISO 4217 fiat only — no crypto. Rates refresh in the background and the last good table keeps working offline.

    166 fiat currency codes

    • 10 EUR to USD
    • $100 in EUR

  • Weather lines

    Current 2 m temperature in Celsius, via Open-Meteo — no key, no GPS: only the city name you type is sent.

    • weather in London

  • Answer tokens & menu

    Double-click any answer to reuse it as a live bubble that follows its source line. Right-click: copy, rounding from 0 to 10 places, delete.

    • Copy Answer
    • 43,5 / 6

  • Sheets & folders

    Named sheets with line numbers, syntax tinting and a live results column, grouped by one-level folder tabs. Drag a sheet onto a tab to re-file it.

  • Styling, constants & portability

    Light or Dark, font size, role colors, decimal places, interface language — all native settings. Every sheet moves as a plain-text .nlx file.

    100 app-wide constants

Local-first, by design

Your sheets live on your Mac and the math runs on your Mac. Numlex makes exactly two kinds of network requests — and they never include your sheet contents.

Local by default

Your sheets stay on your Mac

  • No account
  • No GPS
  • No sync
  • No analytics, no cookies
  • Stored locally Sheets live in ~/Library/Application Support/Numlex — plain files you own and can copy anywhere.
  • Calculations are on-device A strict pure-Swift parser runs everything offline; cached rates and weather keep working with no connection at all.
  • This website No analytics, no cookies, no third-party assets — everything is self-hosted; the only external requests happen when you follow a link.

The only network calls

Your Mac

Numlex — sheets, math, everything local

Currency rates

Background refresh from open.er-api.com (free, no API key) — not per sheet, not per calculation. Cached for an hour; the last good table works offline.

Weather, for the city you type

“weather in London” asks Open-Meteo (no key, no GPS) — only the place name you enter is sent. Cached for ten minutes; the last good value stays on screen if a refresh fails.

Everything else

Nowhere. Sheet contents are never sent — no sync, no telemetry, no collaboration.

Download & install

Free, native Swift, MIT open source. Requires macOS 26 or later on Apple Silicon — there is no Intel build.

Direct download

Get Numlex

A native app — SwiftUI over TextKit, a strict pure-Swift parser, no web view. The button always points at the latest release; 4.6.0 was the latest as of 2026-09-07.

Download for macOS Pinned snapshot: 4.6.0

Homebrew cask

From the terminal

Custom tap (Qulierm/homebrew-tap) — snapshot 2026-09-07: the cask pinned 4.5.1 while the latest release was 4.6.0; the tap can lag, so check it before relying on it for the newest version. 

brew install --cask Qulierm/tap/numlex

Install in three steps

  1. Download the DMG from the latest release and open it — a plain, unstyled disk image.
  2. Drag Numlex.app to Applications.
  3. Launch it from Applications (or Spotlight). If macOS asks about the developer, see the note beside this one.

macOS asks “Numlex.app can’t be opened”

Numlex is signed ad-hoc and is not notarized. If macOS blocks the first launch: Control-click (right-click) Numlex.app → Open → confirm (newer macOS: Open Anyway in System Settings → Privacy & Security). Whether that works depends on your macOS version — see Apple’s guide: open an app from an unidentified developer . Please don’t disable Gatekeeper system-wide.

Frequently asked questions

Why is there no Intel build?
Numlex is a native Apple Silicon app (arm64) for macOS 26 and later. No Intel build exists, so it won't run on Intel Macs.
Is Numlex free?
Yes — it's free and open source under the MIT license. No account, no subscription, no in-app purchases. The source is public on GitHub.
What goes online?
Almost nothing. Sheets are stored locally in Application Support and every calculation runs on your Mac. The only network calls are background refreshes of free currency rates (open.er-api.com) and Open-Meteo weather for the exact city you type. No GPS, no account, no sync.
Can I move my sheets between Macs?
Yes — export a sheet as a .nlx file and import it on another Mac. One edge case: app-wide constants are never embedded in exports, so re-enter them (up to 100) on the receiving Mac.