Unit Converter

Everyday · Works offline

An offline unit converter with every unit at once.

Type a number once and see it in every unit of length, weight, temperature, volume, area, speed or data. It works on a plane, in a basement, anywhere, and there are no ads.

Start using Unit ConverterSee the app

First 100 members: 3 months free · $4.99 a month for every implements tool · No ads · Works offline

Free, no account:Convert units

1 meter is also

  • 100 centimeters
  • 39.37 inches
  • 3.28 feet
  • 1.09 yards

1 meter is also

  • 100 centimeters
  • 39.37 inches
  • 3.28 feet
  • 1.09 yards

In short

Updated

Unit Converter is a web app that converts length, mass, temperature, volume, area, speed and data sizes as you type, and shows the answer in every unit of the category at once. It works offline once it has been opened, on iPhone, Android, Mac and Windows. It uses the exact legal definitions, like 1 inch = 2.54 cm, keeps US and UK pints and gallons apart, and tells a decimal GB from a binary GiB. It comes with implements: $4.99 a month for every tool, with no ads. The converter itself is free in a browser, with no account.

Price
Free in a browser. The app is $4.99 a month or $49.99 a year, with every implements tool
Converts
Length, mass, temperature, volume, area, speed and data
Offline
Yes, once it has been opened. On iPhone, add it to the Home Screen
Precision
6 significant digits, or 4 or 10. Exact answers show in full
Ads
None
Currency
Not included. Exchange rates need a connection

By Rootless Agency. Prices in US dollars.

The story

One number, every unit. Scroll and it plays.

Unit ConverterThe storySkip the story

  1. One number.

    Type it once. That’s all the typing there is.

  2. Every unit at once.

    Meters, feet, miles and nautical miles, all updating as you type. Tap the one you need.

  3. Exact, by definition.

    An inch is exactly 2.54 cm. When an answer is exact, you see all of it, not a rounded guess.

  4. Temperature starts somewhere else.

    Fahrenheit adds 32 as well as multiplying. At −40, the two scales agree.

  5. Three cups, three sizes.

    A US cup is 236.6 mL, a nutrition label cup 240 mL, a metric cup 250 mL. Pick the one your recipe means.

  6. 1 TB, or 931 GB?

    The same drive, counted in thousands or in 1,024s. Nothing is missing.

  7. No signal. Still works.

    Add it to your home screen once. After that it works on a plane, in a basement, anywhere.

How it works

How to convert units offline

Four steps, and the first one only happens once.

  1. Open it once, then add it to your home screen.

    After that it works with no connection. On iPhone, Safari can clear a site after a week unused; Home Screen apps are kept.

  2. Pick what you’re measuring.

    Length, mass, temperature, volume, area, speed or data.

  3. Type the number.

    Sums and fractions work too: 2+3, 1+1/2, 3/4. For lengths, 5’11” means 5 feet 11 inches.

  4. Read every unit at once.

    Tap the one you need to make it the answer, and pin the pairs you use most.

Try it

The same converter as the app, cut down

Live demo

mm = m × 1,000

Every other unit

9 units

  • 1,000Millimeters
  • 100Centimeters
  • 0.001Kilometers
  • 39.3701Inches
  • 3.28084Feet
  • 3 ft 3 3/8 inFeet and inches
  • 1.09361Yards
  • 0.000621371Miles
  • 0.000539957Nautical miles

Good to know

Three questions people keep asking.

Each one has a real answer, and the app shows it without being asked.

Why does a 1 TB drive show 931 GB?

1 TB, counted in 1,000s

Mac, and the box

931 GiB, counted in 1,024s

Windows, as 931 GB

Drive makers count in thousands: 1 TB is 1,000,000,000,000 bytes. Windows counts in 1,024s, divides by 1,073,741,824 and shows 931 GB, though strictly that is 931 GiB. Macs count in thousands and show 1 TB. Nothing is missing.

Is a cup 240 or 250 mL?

236.6 mL

US cup

240 mL

US nutrition label

250 mL

Metric cup

Both, and 236.6 too. A US cup is 8 US fluid ounces, 236.5882365 mL. US nutrition labels use 240 mL, by federal rule. Metric cups, like the ones in Canadian recipes, are 250 mL. Unit Converter lists all three.

Is a UK pint the same as a US pint?

568.26 mL

UK pint, 20 UK fluid ounces

473.18 mL

US pint, 16 US fluid ounces

No. A UK pint is about a fifth bigger. UK gallons and fluid ounces differ from US ones too, so Unit Converter keeps them apart instead of guessing which one you mean.

Exact, by definition

Every one of these is exact, not rounded.

1 inch
2.54 cm
1 foot
30.48 cm
1 yard
0.9144 m
1 mile
1.609344 km
1 nautical mile
1,852 m
1 pound
0.45359237 kg
1 ounce
28.349523125 g
1 US gallon
3.785411784 L
1 UK gallon
4.54609 L
1 acre
4,046.8564224 m²

Exact values from NIST Handbook 44 (2026 edition), Appendix C, and the UK Weights and Measures Act 1985. The 240 mL label cup is in 21 CFR 101.9. Checked September 26, 2026.

Comparison

Unit Converter and the free ones, side by side.

Where the others are better, the table says so: Google and the iPhone Calculator both convert currency.

ComparedUnit ConverterGoogle SearchiPhone CalculatorConverter websitesFree converter apps
PriceFree in a browser. The app comes with every implements tool, $4.99 a monthFreeFree, built inFreeFree with ads, or a paid upgrade
AdsNoneNoneNoneYesUsually
Works offlineYes, once openedNoCurrency needs a connectionNoOften
Every unit at onceYes, as you typeOne pair at a timeOne pair at a timeMostly one pairSome apps
CurrencyNoYesYesSome sitesSome apps
Works oniPhone, Android, Mac and PCAnything with a browseriPhone, iOS 18 and laterAnything with a browserOne platform per app
ComparedUnit ConverterGoogleiPhone Calculator
PriceFree, or $4.99 a month for the appFreeFree
AdsNoNoNo
OfflineYesNoNot for currency
All units at onceYesNoNo
CurrencyNoYesYes

Google’s converter from Google Search Help. iPhone Calculator from Apple’s App Store listing and Apple Support. Websites: unitconverters.net, calculator.net and RapidTables, all paid for by ads. Checked September 26, 2026. Google and iPhone are trademarks of their owners; implements isn’t affiliated with them.

Does Google’s unit converter work offline?

No. It is part of Google Search, so it needs a connection. It does convert currency, which Unit Converter doesn’t, and it shows one pair of units at a time.

Is there a unit converter with no ads?

Yes. The converters built into the iPhone Calculator, Windows Calculator and Mac Spotlight have no ads, and neither does Unit Converter. Most converter websites, and many free converter apps, are paid for by ads.

Questions

Questions people ask.

Short answers, in plain words. Something missing? Ask Support and we’ll add it here.

Is Unit Converter free?
Yes, in a browser: the free unit converter converts every unit with no account and no ads. The app, which installs, works offline and keeps your units on every device, comes with implements, $4.99 a month or $49.99 a year for every tool. The first 100 members get their first 3 months free.
Does it work offline?
Yes, once it has been opened. Everything runs on your device. On iPhone, add it to the Home Screen: Safari can clear a website’s saved files after seven days without a visit, but Home Screen apps keep theirs.
Does it convert currency?
No. Exchange rates change by the minute and need a connection, and Unit Converter is built to work without one.
How accurate is it?
It uses the exact legal definitions, like 1 inch = 2.54 cm and 1 pound = 0.45359237 kg. Answers are rounded to 6 significant digits, or 4 or 10 if you prefer, and an answer that is exact, like 1 mile = 1.609344 km, always shows in full.
Can I type fractions?
Yes: 1+1/2, 3/4, and sums like 2+3. For lengths, 5’11” means 5 feet 11 inches. Inches can also show as fractions, to the nearest 1/16 or whatever you pick.
Does it tell US and UK units apart?
Yes. US and UK pints, gallons and fluid ounces are listed separately, and so are the US cup, the nutrition label cup and the metric cup.
Which units does it cover?
Length from millimeters to nautical miles, mass from milligrams to US tons, Celsius, Fahrenheit and Kelvin, volume from teaspoons to cubic meters, area from square centimeters to square miles, speed including knots, and data from bits to tebibytes.
Does it remember my units?
Yes. It opens where you left off. While you’re signed in, your last units and your pinned pairs follow you to your other devices.
Can I add it to my home screen?
Yes. On iPhone, open Share in Safari and tap Add to Home Screen. On Android, tap Install app, or Add to home screen in Chrome’s menu. On a computer, install it from Chrome or Edge.
Does it work on a computer?
Yes, in its own window. Press / to pick a unit, S to swap and C to copy the answer.

Also included

Every other tool, same subscription.

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