The quick version: Most people install Numi, type a currency conversion, and never open Preferences again. That leaves most of the app unused. The ten features below, from the global hotkey to number base conversion, take two minutes each to turn on and change how much of your daily math actually runs through the app.
1. The global hotkey
Numi doesn’t need to live in a window you switch to. Set a shortcut in Preferences → General → Global Hotkey, and the app drops down over whatever you’re doing, the same way Spotlight does. Mine is ⌥Space. Without this, Numi is just another app in the dock. With it, it’s the fastest calculator you own.
2. Variables
Write “hourly = $65” on line one and reference hourly on every line after it. Raise your rate once at the top of the sheet and every dependent calculation below updates on its own. Freelancers who quote projects in the Numi app build entire estimate templates this way and never retype a number.
3. Custom functions
Beyond variables, Numi lets you define reusable formulas. Set up something like a tip calculator that takes a bill and a percentage, name it, and call it by name on any line afterward. It behaves like a spreadsheet formula that reads as a sentence instead of a cell reference.
4. Line comments
Start a line with // and Numi treats it as plain text, skipped entirely by the math engine. This turns a calculation sheet into something closer to a lab notebook — the numbers and the reasoning behind them living on the same page, which matters six months later when you reopen a quote and can’t remember why a number is what it is.
5. Multiple documents
Numi isn’t limited to one running sheet. Keep a document for monthly budgeting, another for client invoices, another for unit conversions you look up constantly. Each stays independent with its own variables, so a rate defined in one document doesn’t leak into another.
6. Result-only copy
Hover a result and Numi offers to copy just the number, stripped of the surrounding text. It sounds small until you’re pasting forty line items into an invoice and don’t want to hand-edit each one afterward.
7. Unit shorthand chains
You can chain conversions in a single line instead of writing them one at a time: “3 kg to lb to oz” returns both conversions without a second line. Most people discover this by accident. It’s worth doing on purpose.
8. Previous-line reference
Type “prev” or “ans” and Numi pulls the result from the line directly above. This turns a multi-step calculation into a running chain: compute a subtotal, reference it with prev on the next line to add tax, reference that with prev again to add a tip, without retyping any intermediate number.
9. Themes and font size
Preferences includes a handful of visual themes and an adjustable font size, separate from your system-wide macOS appearance. If Numi lives on screen for hours at a time, bumping the font up two sizes is the kind of change you make once and immediately wonder why you waited.
10. Number base conversion
Type a hex value like “0x1F in decimal” or a binary string and Numi converts it inline, alongside normal octal handling. Developers checking byte sizes or debugging a bitmask get this for free inside the same document as their currency and budget calculations, in the Numi calculator they already have open.
Turning these on is the whole trick
None of this requires a plugin or a workaround, it’s all sitting in Preferences and in the syntax the parser already understands. The gap between “I use Numi for currency conversion” and “Numi replaced four other tools” is usually just these ten settings, tried once each. Grab Numi for macOS if you haven’t, and if you have, open Preferences today and set the hotkey first. Everything else follows from that one habit change.
Frequently asked questions
How do I set a global hotkey for Numi?
Open Numi Preferences, go to General, and assign a shortcut under Global Hotkey. Once set, that combination brings Numi to the front from inside any app.
Can Numi reference the line above it?
Yes. Typing “prev” or “ans” on a new line pulls in the result from the line directly above, useful for chaining calculations without retyping numbers.
Does Numi support hex and binary?
Yes. It understands hex, binary, and octal notation and converts between number bases in the same line, which developers use for byte size and bitwise math.
Can I write my own functions in Numi?
Yes, in the paid tier. Define a formula once with named inputs, then call it by name on any line, similar to a spreadsheet formula written as a sentence.