A Mac unit converter one hotkey away.
Type 5km to miles and the answer is on screen before you finish the line. Type 5km on its own and every other length unit comes back at once, so you can read down instead of deciding first. Twenty-five units across four families, parsed on your own machine, with no network in the loop at any point.
What a Mac unit converter is actually for
The conversions that interrupt you are never interesting ones. A recipe in cups when your scales read grams. A monitor spec in inches when your tape measure is centimetres. An oven at 375°F. A parcel in pounds. Each is four seconds of thought, and then a browser tab, a page of adverts, a cookie banner, two boxes — and the sentence you were writing has gone.
A Mac unit converter that lives in a launcher removes the trip rather than speeding it up. Press the hotkey you already press for everything else, type the number and the unit, read the answer. Return copies it and the panel closes. Nothing loads and nothing is fetched, which for units is less about privacy than about working identically on a train, in a basement, and on a plane.
Coco’s unit conversion shares one panel with app launching, clipboard history, arithmetic and currency, written in Swift against AppKit rather than a web view in a window. The whole table is compiled into the app: twenty-five unit definitions, each with a scale, an offset and a list of aliases. No lookup, no service, no first-run download. Currency conversion is a separate feature with live rates and has its own page, as does the calculator.
What this Mac unit converter actually converts
Four families, twenty-five units
Length: mm, cm, m, km, in, ft, yd, mi. Mass: mg, g, kg, oz, lb. Volume: ml, l, tsp, tbsp, floz, cup, pt, qt, gal. Temperature: C, F, K. That is the entire list. Each unit answers to its spelled-out name and plural as well as its symbol, and both metric spellings: kilometre and kilometer, litres and liters, plus lbs, teaspoons, fluidounce and centigrade.
Type it the way you would say it
Four shapes parse: 5km to miles, 5 km in mi, the bare pair 5 km mi, and 5km with no target at all. Case is irrelevant and the space between number and unit is optional. Decimals and a leading sign work: 2.54cm, -40f to c, +12 in ft. One thing does not — a thousands separator. 1500 m converts, 1,500 m does not.
Leave the target off and get the whole family
5km with nothing after it returns every other length unit at once: miles, yards, feet, inches, metres, centimetres, millimetres. Not one guess, seven answers — the shape of the question when you are reading a spec sheet and do not yet know which unit you want out of it. Each row shows the converted figure with the original underneath.
Temperature is an offset, not a ratio
Celsius, Fahrenheit and Kelvin each carry a scale and an offset instead of a plain multiplier, which is the part quick converters get wrong. -40f to c returns -40. 0c in k returns 273.15. 100f to c gives 37.777778. Fahrenheit is stored as five ninths with a 32-degree offset, Kelvin as Celsius shifted by 273.15; celsius, centigrade, fahrenheit, kelvin and kelvins all match.
What it will not convert
No data units, so mb to gb returns nothing. No time, speed, area, energy, pressure or angle either. Volume is US customary throughout — a cup is 236.588 ml, a pint 473.176 ml, a gallon 3.785 l — so UK pints and gallons are not in the table, and there is no tonne, stone or nautical mile. Mixing families is refused rather than guessed at: kg to cm gives nothing.
How the number comes out
Up to six decimal places with trailing zeros trimmed, so 1 in to cm reads 2.54 rather than 2.540000. Anything within a billionth of zero prints as a clean 0 instead of a floating-point ghost. There are no thousands separators, which is what makes the figure safe to paste straight into a spreadsheet cell. Return copies value and unit together — 8.04672 km.
This Mac unit converter next to Spotlight, Raycast and Alfred
Unit conversion is not a rare feature and it would be silly to pretend otherwise. Spotlight converts units, is already on your Mac, and costs nothing — if you convert inches to centimetres twice a month, use Spotlight and keep your money. For a lot of people it covers the common cases and that is the end of the question. Raycast includes unit conversion in its free tier, Pro being $8 a month for other things. Alfred does it through workflows in the paid Powerpack, around £34 once.
What differs here is narrow: the whole family at once when you leave the target off, a grammar you can learn in one line, and nothing over the network at any point. What differs the other way is just as narrow. Coco covers four families and twenty-five units; a dedicated conversion app, and Spotlight itself, will handle data sizes, areas and time that Coco does not. A mac unit conversion app that covers everything is not what this is.
| Coco | Spotlight | Raycast | Alfred | |
|---|---|---|---|---|
| Unit conversion in the launcher | Workflow | |||
| Length, mass, volume, temperature | Workflow | |||
| Whole family at once, no target needed | ||||
| Data, time, speed and area units | Some | Some | Workflow | |
| Currency conversion in the same field | Workflow | |||
| Works with no network | Mostly | |||
| One-time purchase, no account | Included | |||
| Price | $49 once | Included | Free or $8/mo | £34 once |
Converting units in Coco
Install it and press the hotkey
Drag Coco into Applications and open it once. Conversion needs no setting up and no account: the unit table ships inside the app, so it answers on the first launch with the network off. macOS 14 or later, Apple Silicon.
Type a number and a unit
5km, 5 km, 180lb, 2.54cm, 375f. The space is optional and capitals do not matter. Conversions only appear when nothing else claims the query, so an app name still wins the panel: type kg and you get your apps, type 5kg and you get grams.
Name a target, or read down the list
5km to miles for one answer; 5 km in mi and 5 km mi do the same thing. Leave the target off and the whole family comes back at once, with the source figure repeated under each row so you can see which way round the conversion went.
Press Return to copy
Return copies the highlighted row — the value with its unit, such as 3.106856 mi — and closes the panel. The figure carries no thousands separators, so it drops into a spreadsheet cell without being reformatted first.
Questions people actually ask
- How do I convert units on a Mac without opening a browser?
- Use a launcher that converts in its own panel. In Coco you press the hotkey and type the number and the unit together: 5km to miles, 180 lb in kg, 375f to c. The result appears as you type, and Return copies it and closes the panel. Nothing is fetched, so it behaves the same offline as online. Leaving the target off — just 5km — returns every other unit in that family at once. Spotlight also converts units, is already installed, and is free; for occasional conversions it is the sensible answer.
- Which units does Coco convert?
- Twenty-five units in four families. Length: millimetres, centimetres, metres, kilometres, inches, feet, yards, miles. Mass: milligrams, grams, kilograms, ounces, pounds. Volume: millilitres, litres, teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons. Temperature: Celsius, Fahrenheit, Kelvin. Every unit matches on its symbol, its spelled-out name and its plural, and metric units accept both the -re and -er spellings, so kilometre and kilometer are the same token. Volume is US customary: a cup is 236.588 ml and a pint 473.176 ml, which means UK pints and gallons are not represented. Conversions between different families are rejected rather than approximated.
- How should I write the query — does 5km to miles work?
- Yes, and three other forms do too. 5km to miles, 5 km in mi, the bare pair 5 km mi, and 5km with no target at all, which lists the whole length family. The space between number and unit is optional and capitalisation is ignored, so 5KM and 5 km are identical. Decimals work, and so does a leading plus or minus, which is what makes -40f to c a valid query. The one thing that fails is a thousands separator: 1500 m converts, 1,500 m does not, because the number is read as a plain prefix before the unit.
- Does Coco convert data sizes, time, speed or area?
- No. The table holds length, mass, volume and temperature and nothing else, so mb to gb, 90 min to hours, 60 mph to kph and 500 sqft to sqm all return nothing rather than a wrong answer. Tonnes, stones and nautical miles are absent for the same reason. If those are the conversions you do daily, Spotlight or a dedicated conversion app is the better tool. What Coco covers is the everyday physical set — a recipe, a parcel, a spec sheet, an oven — and it covers that set completely rather than partially covering ten families.
- How does temperature conversion work, and does -40 work?
- Each temperature unit carries a scale and an offset rather than a single multiplier, so the 32-degree shift between Fahrenheit and Celsius and the 273.15 shift for Kelvin are applied properly instead of being treated as ratios. -40f to c returns -40, the one point where the two scales meet. 0c in k returns 273.15, and 100f to c gives 37.777778. Negative values are accepted anywhere a number is, so -12c in f is a valid query. The aliases celsius, centigrade, fahrenheit, kelvin and kelvins all resolve, as do the bare letters c, f and k.
- Is Coco’s unit converter better than Spotlight’s?
- Not across the board, and it would be dishonest to claim so. Spotlight is free, already running, and handles categories Coco does not have at all. Three things differ. Coco returns the entire family when you omit the target, so one query answers a question you have not fully formed. The grammar is fixed and written down, so you can rely on it instead of testing what the parser accepts today. And conversion sits in the same field as app launching, clipboard history, arithmetic and currency, so it is one hotkey rather than several. If none of that matters, stay with Spotlight.
- What does it cost, and does unit conversion need a network?
- Unit conversion never touches the network. The whole table is compiled into the app, so it answers on a first launch with Wi-Fi off, in a basement, or on a plane; only currency conversion, a separate feature, fetches anything. The app is seven days free with no card and no account, then $49 once for one Mac, currently $39 during the launch promotion. It is a one-time purchase rather than a subscription, updates within this major version are included, and there is a 30-day refund. Coco needs macOS 14 or later and Apple Silicon.