Unit Converter

About this tool

Convert between common length, weight, and temperature units. Pick a category, choose the "from" and "to" units, and the result updates as you type. "Swap units" flips the direction without re-entering anything.

How length and weight conversion works. Every unit within a category is defined as a fixed multiple of one base unit — meters for length, grams for weight. To convert, the tool turns your input into the base unit and then into the target unit, so the path is always exact regardless of which two units you pick. That's why 1 mile shows as exactly 1609.344 meters and 1 inch as exactly 25.4 millimeters — those are defined values, not measurements.

Why temperature is different. Temperature scales don't share a zero point: 0 °C is 32 °F, not 0 °F. So each pair needs its own formula rather than a single factor. °C to °F is (C × 9/5) + 32; °C to K is C + 273.15. Kelvin has a true absolute zero, so the tool rejects values below 0 K as physically impossible.

Worked examples. 100 km is 100 × 1000 ÷ 1609.344 = about 62.14 miles. 200 °F is (200 − 32) × 5/9 = about 93.3 °C. 5 kg is 5 × 1000 ÷ 28.349523 = about 176.4 ounces.

US vs. imperial gallons and pints. This tool covers length, weight, and temperature, which are unambiguous. Volume is not: a US gallon is about 3.785 liters, an imperial (UK) gallon about 4.546. If you branch out to volume elsewhere, always check which system a "gallon" or "pint" refers to.

Weight vs. mass. In everyday use "weight" in kilograms or pounds really means mass, and that's how this converts. True weight is a force and depends on gravity; the distinction only matters in physics contexts.

For recipe quantities like cups, tablespoons, and grams of flour, use the cooking converter, which accounts for ingredient density. For screen and print sizing, see the aspect ratio calculator.

Frequently asked questions

Which units are supported?

Length: millimeters, centimeters, meters, kilometers, inches, feet, yards, miles. Weight: milligrams, grams, kilograms, ounces, pounds. Temperature: Celsius, Fahrenheit, Kelvin.

Why does temperature work differently from length and weight?

Temperature scales aren't simple multiples of one another because they don't share a zero point, so the tool applies the correct formula for each pair instead of one conversion factor.

Can I convert Kelvin below zero?

No. Kelvin starts at absolute zero, so negative values are rejected as physically invalid.

Are the conversion factors exact?

Yes for the defined ones — 1 inch is exactly 25.4 mm and 1 mile is exactly 1609.344 m by international agreement. Results are rounded only for display.

Does it handle volume, like gallons or liters?

Not in this tool. Volume units are ambiguous between US and imperial systems, so they're handled separately where needed.

Is a kilogram a unit of weight or mass?

Strictly it's mass, but in everyday use "weight" and "mass" are used interchangeably, and that's how this converts. The difference only matters in a physics context.