Unit Conversion Calculator

How to use the converter

1. Pick a category — length, weight, volume, area, speed, digital storage or temperature.
2. Select the unit you are converting from and the unit you are converting to.
3. Enter a value and press Convert to read the result.

Switching category refreshes the available units automatically, so the "from" and "to" lists always match what you are measuring. You can swap the direction just by reversing your unit choices.

What it converts

Each category holds the units that people most often need to move between:

• Length — millimetres, centimetres, metres, kilometres, inches, feet, yards and miles.
• Weight / mass — milligrams, grams, kilograms, tonnes, ounces, pounds and stone.
• Volume — millilitres, litres, cubic metres and US teaspoons, tablespoons, fluid ounces, cups, pints, quarts and gallons.
• Area — square centimetres, square metres, hectares, square kilometres, square feet, acres and square miles.
• Speed — metres per second, km/h, mph, knots and feet per second.
• Digital storage — bytes through terabytes, in both decimal (KB, MB, GB) and binary (KiB, MiB, GiB) units.
• Temperature — Celsius, Fahrenheit and Kelvin.

How factor-based conversion works

Every unit in a category stores a factor to that category's base unit — metres for length, kilograms for mass, litres for volume, square metres for area, metres per second for speed and bytes for storage. To convert, the tool multiplies your value by the "from" factor to reach the base unit, then divides by the "to" factor to reach the target unit.

That two-step design keeps every pair consistent: because one mile is defined as exactly 1,609.344 metres and one kilometre as 1,000, a mile is always precisely 1.609344 kilometres, with no rounding drift between them.

A worked example

Convert 5 miles to kilometres. Miles carry a factor of 1,609.344 metres and kilometres a factor of 1,000, so the result is 5 × (1,609.344 ÷ 1,000) = 5 × 1.609344 = 8.047 kilometres. Reverse it and 100 km is 100 × (1,000 ÷ 1,609.344) ≈ 62.14 miles.

Common conversions at a glance

From	To	Multiply by
Miles	Kilometres	1.609
Kilograms	Pounds	2.205
Inches	Centimetres	2.54
US gallons	Litres	3.785
Celsius	Fahrenheit	× 9/5, then + 32

Why temperature is different

Temperature scales do not share a zero point, so they use formulas rather than a single multiplier. The converter routes every temperature through Celsius and applies the standard relationships:

Conversion	Formula
Celsius → Fahrenheit	(°C × 9/5) + 32
Fahrenheit → Celsius	(°F − 32) × 5/9
Celsius → Kelvin	°C + 273.15

So 20°C is (20 × 9/5) + 32 = 68°F, and also 20 + 273.15 = 293.15 K.

Decimal vs binary storage

Digital storage has two conventions, and the calculator supports both. Decimal units step by 1,000 — a kilobyte is 1,000 bytes — while binary units step by 1,024, so a kibibyte (KiB) is 1,024 bytes and a mebibyte (MiB) is 1,048,576. Drive makers quote decimal gigabytes while operating systems often report binary ones, which is why a "1 TB" disk can look slightly smaller once installed.

All factors are the internationally defined values, so results are exact and only rounded for display. For currency-style financial conversions, see our financial calculators; to turn a floor measurement into an area, try the square footage calculator.