What Is a Unit Converter?
A unit converter turns the same quantity from one unit of measure into another — length from metres to inches, weight from kilograms to pounds, temperature from Celsius to Fahrenheit — accurately and in seconds. This tool covers three categories: length (m, cm, mm, km, inch, foot), weight (kg, g, mg, pound, ounce) and temperature (°C, °F, K). Pick the source and target unit, enter the value, and the result appears instantly.
How to Use It
- Choose the category: length, weight or temperature.
- Enter the value: the number to convert (negative values are valid for temperature).
- Pick source and target units: both must belong to the selected category.
- Click Convert: the result appears instantly and can be copied.
How the Conversion Works
For length and weight, each unit is defined by a factor relative to a base unit — the metre for length, the kilogram for weight. The value is first converted to the base unit, then to the target. For example 100 cm equals 1 metre; 1 inch is exactly 2.54 cm and 1 pound is 0.45359237 kilograms, and this tool uses those official constants. Temperature needs formulas rather than a linear factor, with Celsius as the intermediate: Fahrenheit to Celsius is (°F − 32) × 5/9, Celsius to Fahrenheit is °C × 9/5 + 32, and Celsius to Kelvin is °C + 273.15. So 32 °F is exactly 0 °C and 100 °C is 212 °F.
Use Cases
- Shopping abroad: convert a screen size in inches or a shipping weight in pounds to the metric system.
- Cooking: turn ounces and Fahrenheit in foreign recipes into grams and Celsius.
- Education and engineering: switch between units quickly in homework, experiments and technical calculations.
- Travel: convert weather (°F) and distance (km vs miles) into the units you are used to.
Tips and Common Mistakes
- Stay in one category: source and target must be the same category; converting length to weight is meaningless and the tool prevents it.
- Zero is special for temperature: 0 °C is not 0 °F. Temperature conversion needs a formula, not a simple ratio.
- Inch vs foot: 1 foot is 12 inches; check which unit you entered.
Metric and Imperial Systems
Most of the world uses the metric system (metre, kilogram, Celsius), while some countries, notably the US, keep imperial/US units (inch, foot, pound, Fahrenheit). This split creates a constant need to convert when shopping abroad, following foreign recipes or reading technical documents. A "55-inch" TV screen is about 140 centimetres; a height of 5 ft 10 in is roughly 178 centimetres; 1 pound is just over half a kilo (0.4536 kg). Because this tool uses official constants, results come from exact factors rather than rounded guesses.
Temperature conversion needs special care because the scales have different zero points. Water freezes at 0 Celsius, 32 Fahrenheit and 273.15 Kelvin; it boils at 100 Celsius, 212 Fahrenheit and 373.15 Kelvin. You therefore cannot convert temperature with a simple ratio (like doubling); a formula is required, and the tool applies it for you. When a recipe says "350°F oven", this tool gives you roughly 177 Celsius in a second so you can set your oven correctly.
The values you enter are never stored. To convert colour codes, see our Color Code Converter, and for screen and image proportions the Aspect Ratio Calculator. If your web or mobile project needs custom calculation and conversion modules, our custom software development service can help.