Spotlight as a calculator and unit converter

A quick calculation or conversion is one shortcut away on a Mac. You don't have to open the Calculator app to figure out a total with tax, and you don't have to search the browser for "km to miles converter" — Spotlight handles both right in the search field, with no page to wait for. It works as a small but frequently used helper handy for dozens of people in the office and beyond — from an accountant to a student working through physics notes.

A typical scenario

While putting together a proposal, you need to quickly calculate a price with tax, and then immediately figure out what that comes to in euros for a foreign client. The usual route is to open Calculator, type the calculation, remember or copy the result, then open a browser and find the current exchange rate — three different apps for one quick number.

With Spotlight, one shortcut and a few words are all it takes. Type an expression with tax, get the result instantly, press the shortcut again, and type the currency conversion — no other app or tab needed.

How to do it

1. Press Cmd + Space — a search field opens in the middle of the screen.
2. Type a math expression, for example "1590*1.21" — the result appears instantly right below the field, before you've even finished typing the full expression.
3. Spotlight also handles parentheses and basic functions, so it can compute more complex multi-step expressions too.
4. To convert currencies, type something like "100 eur in usd" — Spotlight pulls the current exchange rate and does the conversion on the spot.
5. Unit conversions work the same way: "5 miles in km," "350 f in c" (Fahrenheit to Celsius), or converting kilograms to pounds.
6. Copy the result with Cmd + C right from the Spotlight window, without having to select anything with the mouse — then just paste it wherever you need it.
7. Spotlight computes percentages directly too — type an expression with a percentage (say, a discount off a price) and the result appears just as instantly as with plain multiplication or division.

The best tools

• Built-in Spotlight (Cmd + Space) — free, an instant result, works offline for purely mathematical expressions.
• The Calculator app — for longer or scientific calculations with memory for intermediate results, where Spotlight isn't the right fit.
• Raycast — a free Spotlight replacement with expanded calculation options, custom shortcuts, and a clearer history of recent queries.
• PCalc (a paid app) — for power users who calculate often and want advanced functions and desktop widgets.

What you get out of it

• Time: no more opening Calculator and a browser just for one number — for small calculations throughout the day, that's a real few minutes saved.
• Flow: you don't interrupt what you're doing by switching to another app; the result appears in a window that closes itself.
• Current rates: currency conversions use a continuously updated exchange rate, so you don't have to look it up and plug it in yourself.
• Less risk of error: the calculation and the result are both in one place, making it easier to check you didn't enter the wrong number than when you're just remembering the result from a different app.

Pro tip

Spotlight remembers recent calculations in its search history — if you need the same conversion again, just start typing a similar query and the autocomplete will suggest what you calculated last. This is handy for repeated conversions, like the same exchange rate multiple times in one day, so you don't have to retype the whole expression from scratch.