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Unit Converter — Length, Weight, Temperature & More
Convert between metric and imperial units for length, weight, temperature, volume, area, speed, digital storage and time — with the conversion formula shown, adjustable precision and a reference table for every category.
Metric and imperial
Formula shown every time
Converts as you type
No sign-up, nothing stored
Convert any unit
Pick a category, choose your units and type a value. The result updates instantly — nothing is uploaded or stored.
Why this converter
One converter for eight categories, with the maths on show
Most converters give you a number and nothing else. This one shows the formula it used, adapts precision to the size of the result, and lists the conversions people actually look up.
The formula, every time
Each result shows the exact multiplier or equation used, so you can check the work, reuse it in a spreadsheet or teach it to someone else.
Smart precision
Automatic mode keeps significant digits when a result is tiny or enormous, and you can lock it to a fixed number of decimals when you need clean figures.
One-tap swap
Flip the direction of any conversion instantly — useful when you realise you needed inches to centimetres rather than the other way round.
Live reference list
Alongside your answer you get the same value converted into every other unit in the category, so one entry answers several questions at once.
Fast, private, offline-friendly
No account, no ads over the tool and no data leaving your device. It converts as you type and stays usable on a poor connection.
How to use it
How to convert units in four steps
Pick a category
Choose length, weight, temperature, volume, area, speed, data or time from the buttons at the top.
Choose your units
Set the unit you have and the unit you want. Tap the swap button to reverse the direction.
Type your value
The result appears as you type, along with the formula and the equivalent in every other unit.
Set the precision
Leave it automatic, or lock the answer to a fixed number of decimal places for clean reporting.
Benefits
Where getting the conversion right actually matters
Unit mistakes are cheap to make and expensive to fix — the same slip that ruins a recipe has grounded aircraft and lost spacecraft.
Cooking from foreign recipes
Grams to ounces, Celsius to Fahrenheit and millilitres to cups, without guessing halfway through a bake.
DIY and construction
Plans in millimetres, timber sold in feet and a tape measure in inches — convert once and cut once.
Travel and driving abroad
Kilometres per hour to miles per hour, litres to gallons and Celsius to Fahrenheit at a glance.
Shipping and logistics
Carriers quote in kilograms or pounds and centimetres or inches; the wrong unit means the wrong price band.
Storage and bandwidth
Understand why a 1 TB drive shows as roughly 931 GB once your operating system counts in binary.
Homework and coursework
Seeing the formula alongside the answer means you can show your working rather than just copying a number.
The method
How unit conversion works
Everything runs through a base unit
Almost every conversion is a two-step multiplication. The value is converted into the category’s base unit, then out again into the target unit. For length the base is the metre, so converting 10 feet to centimetres means 10 × 0.3048 = 3.048 metres, then 3.048 ÷ 0.01 = 304.8 centimetres. That is why the converter can show a single multiplier for any pair of units.
Temperature is the exception
Temperature scales have different zero points, so they need an offset rather than a simple ratio. Celsius to Fahrenheit is °F = °C × 9/5 + 32, Fahrenheit to Celsius is °C = (°F − 32) × 5/9, and Kelvin is Celsius plus 273.15. The two scales meet at −40, which reads the same in both.
The conversions people look up most
| Conversion | Exact factor | Quick mental version |
|---|---|---|
| Inches to centimetres | × 2.54 | Two and a half times |
| Feet to metres | × 0.3048 | Divide by 3, take off a little |
| Miles to kilometres | × 1.609344 | Add 60 percent |
| Pounds to kilograms | × 0.45359237 | Halve it, add back a bit |
| Kilograms to pounds | × 2.20462 | Double it, add 10 percent |
| Litres to US gallons | ÷ 3.785412 | Divide by four, round up |
| Celsius to Fahrenheit | × 9/5 + 32 | Double it and add 30 |
| km/h to mph | × 0.621371 | Take off about a third |
Watch out for units that share a name
- Gallons: a US gallon is 3.785 litres, an imperial gallon is 4.546 litres — about 20 percent larger.
- Fluid ounces: the US fluid ounce is slightly larger than the imperial one, despite the imperial pint being bigger overall.
- Tons: a metric tonne is 1,000 kg, a US short ton is 907 kg and a UK long ton is 1,016 kg.
- Cups: US, metric and UK cups all differ, which is why weighing ingredients is more reliable than measuring by volume.
- Storage: drive makers count 1 GB as 1,000,000,000 bytes while operating systems often count 1,073,741,824.
Precision and rounding
Conversion factors like 2.54 for inches to centimetres are exact by definition, while others are rounded decimals. Rounding too early compounds the error, so convert first and round last, and keep more decimal places than you think you need when a result feeds into another calculation.
FAQ
Unit converter questions, answered
How do I convert inches to centimetres?
Multiply the number of inches by 2.54, since one inch is defined as exactly 2.54 centimetres. So 12 inches is 30.48 centimetres and 6 inches is 15.24 centimetres. To go the other way, divide centimetres by 2.54.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8) and add 32. So 20°C is 68°F and 37°C is 98.6°F. For a rough mental estimate, double the Celsius figure and add 30 — close enough for weather, though it drifts at extremes.
How many kilograms are in a pound?
One pound is 0.45359237 kilograms, so a kilogram is about 2.2046 pounds. To convert pounds to kilograms, divide by 2.2046 or multiply by 0.4536. A useful mental shortcut is to halve the pounds and then add roughly ten percent back.
What is the difference between a US and an imperial gallon?
A US gallon is 3.785 litres while an imperial gallon used in the UK is 4.546 litres, about 20 percent larger. The same difference runs through quarts, pints and fluid ounces, so always check which system a recipe or fuel figure is using.
Why does my 1 TB hard drive show less than 1 TB?
Manufacturers count 1 TB as one trillion bytes, while many operating systems display storage in binary units where 1 TB is 1,099,511,627,776 bytes. The drive is not smaller than advertised; it is being measured with a different definition, which is why 1 TB typically shows as about 931 GB.
Is this unit converter accurate?
It uses internationally defined conversion factors and full floating-point precision, rounding only at the display stage. For most practical purposes the results are exact. For laboratory, engineering or legal work, confirm against the relevant standard, since some factors are rounded definitions and some units vary by jurisdiction.
Can I convert between metric and imperial units?
Yes — every category mixes both systems, so you can convert metres to feet, kilograms to stone, litres to gallons, square metres to acres and kilometres per hour to miles per hour. Use the swap button to reverse the direction of any conversion in a single tap.
Convert any unit in seconds
Free, private and instant — eight categories, metric and imperial, with the formula and every other unit in the category shown alongside your answer.
This unit converter is provided for general use. Conversion factors follow international definitions, but some units differ by country or industry — gallons, tons, cups and fluid ounces in particular. For engineering, medical, legal or laboratory work, verify results against the standard that applies in your field.