Unit converter

Most of the world uses the metric system — a decimal-based system of measurement adopted internationally after the French Revolution. Its appeal is simplicity: every unit is a power of ten apart, so converting kilometres to metres is just a matter of moving the decimal point.

The United States, Myanmar, and Liberia are the only countries that have not officially adopted the metric system as their primary system of measurement. The US uses a variant of the old English imperial system — US customary units — which evolved from trade and colonial-era standards that predate standardization.

The UK sits in an interesting middle ground: officially metric since the 1960s, but road signs still display miles, body weight is commonly given in stone and pounds, and beer is still served in pints. For anyone working across these systems — in travel, cooking, engineering, or science — a reliable unit converter is an everyday necessity.

Temperature is the one unit category where you can't simply multiply by a fixed number — you also need to add or subtract an offset. This is because Celsius and Fahrenheit have different zero points.

Celsius sets 0° at the freezing point of water and 100° at boiling (at sea level). Fahrenheit sets 32° at freezing and 212° at boiling — a quirky scale developed by Daniel Gabriel Fahrenheit in the early 1700s, originally calibrated using a brine solution for 0° and human body temperature for 96°.

Kelvin is the SI unit of temperature used in science. It starts at absolute zero — the theoretical point at which all molecular motion stops, equal to −273.15°C. Unlike Celsius and Fahrenheit, Kelvin has no negative values, which makes it useful in thermodynamics equations.

Some useful reference points: water freezes at 0°C / 32°F, a comfortable room is around 20°C / 68°F, body temperature is 37°C / 98.6°F, and water boils at 100°C / 212°F.

In September 1999, NASA's Mars Climate Orbiter was lost as it approached Mars. The cause: one engineering team had been sending thruster data in imperial units (pound-force seconds), while the navigation software expected metric units (newton-seconds). The spacecraft entered the Martian atmosphere at the wrong angle and was destroyed.

The $327 million mission failure is now one of the most cited examples of why unit consistency matters in engineering. It's also a good reminder that unit conversion errors aren't just an inconvenience — in the wrong context, they have serious consequences.

This unit converter handles length, weight, temperature, speed, volume and area using internationally recognised conversion factors. Conversions update instantly as you type in either field. Use the swap button to reverse direction. The copy link button encodes your exact conversion in the URL so you can share it with anyone. Recent conversions are saved locally in your browser for quick access.