Unit Converter
Seven families of units, dozens of conversions, one box — with the most useful related conversions shown alongside.
Result
What this calculator does
Most of the world measures in metres and kilograms; the United States does not; the UK uses a mixture that changes depending on whether you are buying petrol, milk or carpet. Recipes cross borders, packages cross borders, and gym equipment is labelled in whichever unit the manufacturer preferred. So conversion comes up constantly.
This converter covers seven families: weight, length, temperature, volume, area, speed and digital storage. Pick a category, type a number, and the answer appears as you type — along with the same value in several other units from the same family, which is often what you actually needed. A swap button flips the direction in one tap.
How to use it
- Choose a category. The two unit lists refill with sensible defaults for that family.
- Type the amount. The conversion updates live, with more decimal places for small numbers.
- Use the swap button between the two lists to reverse the direction without retyping anything.
- Look below the main result for the same value in other units of the same family — handy when a recipe gives cups and your jug is in millilitres.
The formula
Most conversions are a single multiplication through a base unit:
result = value × (factor of the source unit) ÷ (factor of the target unit)
Temperature is the exception, because the scales have different zero points:
°C → °F F = C × 9/5 + 32
°F → °C C = (F − 32) × 5/9
°C → K K = C + 273.15
Factors use the exact internationally agreed definitions — one inch is exactly 25.4 mm and one pound is exactly 0.45359237 kg — so the results are not approximations.
Worked examples
| Scenario | What you enter | Result |
|---|---|---|
| 70 kilograms into pounds | Weight | 154.3236 lb |
| 180 centimetres into feet | Length | 5.9055 ft — about 5 ft 11 in |
| 100 °F into Celsius | Temperature | 37.7778 °C |
| 2 US cups into millilitres | Volume | 473.1765 ml |
| 120 km/h into miles per hour | Speed | 74.5645 mph |
Frequently asked questions
Multiply by 2.2. For a closer figure use 2.20462 — 70 kg is 154.32 lb. Going the other way, divide by 2.2, or halve and subtract ten percent for a rough answer. The definition is exact: one pound is 0.45359237 kilograms, fixed by international agreement in 1959, so this is a conversion with no ambiguity at all.
Double it and add 30. Twenty degrees becomes about 70 °F, which is close enough for weather (the exact answer is 68 °F). The precise formula is F = C × 9/5 + 32. The two scales cross at −40, where both read the same number — a useful check if you ever suspect you have the formula upside down.
History. The US gallon is based on an old English wine gallon of 231 cubic inches, about 3.785 litres. The imperial gallon, defined in the UK in 1824, is about 4.546 litres — roughly 20% larger. This matters enormously for fuel economy figures: a car doing 30 miles per US gallon does 36 per imperial gallon. Both are listed separately here.
Not quite, and it trips up bakers. A US cup is about 237 ml, a metric cup used in Australia and much of Europe is 250 ml, and the UK traditionally used 284 ml. Teaspoons and tablespoons vary too — the Australian tablespoon is 20 ml against 15 ml almost everywhere else. This converter uses US measures, so check which system your recipe assumes.
Both answers are in use, which is why your drive looks smaller than the box claimed. Storage manufacturers use powers of ten, where a gigabyte is 1,000 megabytes. Operating systems usually use powers of two, where it is 1,024 — properly called a gibibyte. This converter uses the binary convention, matching what your computer reports.
They use the exact internationally agreed definitions and full double-precision arithmetic, so the only rounding happens at the display step. Results show four to six decimal places depending on the size of the number. For engineering work where the last digit matters, note that your input precision, not the conversion, is almost always the limiting factor.
The seven categories cover the conversions people search for most, with eight or nine units in each. If something you need is missing — nautical measures, cooking weights by ingredient, or currency, which changes by the minute and needs live data — it is not here. The related conversions shown under each result often cover the gap.
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