Unit Converter

Convert Between Units Without the Mental Maths

Measurement gets confusing the moment two systems collide. A recipe lists grams while your scale reads ounces; a hiking trail is marked in kilometres but your map app thinks in miles; an overseas oven dial shows Celsius when you grew up on Fahrenheit. This converter exists to take that friction away. Pick a category, type a number, choose the unit you have and the unit you want, and the answer updates the instant you change anything. There is no Convert-and-wait step, no pop-up, and nothing leaves your device. The seven categories on this page cover the conversions people actually reach for day to day rather than an exhaustive scientific table you would have to scroll through to find the one you need.

The Seven Categories on This Page

Each category has its own set of units, and switching categories instantly repopulates the two dropdowns:

• Length: metres, kilometres, centimetres, millimetres, miles, yards, feet and inches. Useful for everything from a person's height to road distances and the dimensions of a parcel.
• Weight: kilograms, grams, milligrams, pounds, ounces, stones and metric tons. Covers cooking, postage, body weight and shipping.
• Temperature: Celsius, Fahrenheit and Kelvin. The everyday pair is Celsius and Fahrenheit; Kelvin is there for science and engineering work.
• Volume: litres, millilitres, US gallons, UK (imperial) gallons, cubic metres, cubic feet and cubic inches. Note that a US gallon and a UK gallon are not the same size, which is exactly why both are listed separately.
• Digital Storage: bytes, kilobytes, megabytes, gigabytes, terabytes and petabytes. These steps use the binary 1024-based definition, so one kilobyte here is 1024 bytes rather than 1000.
• Area: square metres, square kilometres, square centimetres, square miles, square yards, square feet, acres and hectares. Handy for room sizes, land plots, and property listings.
• Speed: metres per second, kilometres per hour, miles per hour, knots and feet per second. Useful for vehicle speeds, wind and weather reports, and nautical or aviation figures.

Everyday Conversions People Search For

Most conversions come down to a handful of well-worn pairs. Here are the common ones and roughly what to expect, so you can sanity-check a result at a glance:

• Centimetres to inches: divide by 2.54. So 30 cm is about 11.8 inches, and a 15 cm phone is just under 6 inches.
• Kilograms to pounds: multiply by about 2.205. A 70 kg person weighs roughly 154 pounds, and a 5 kg parcel is about 11 pounds.
• Celsius to Fahrenheit: multiply by 9, divide by 5, then add 32. Body temperature of 37°C is 98.6°F, and a warm 25°C day is 77°F.
• Kilometres to miles: multiply by about 0.621. A 10 km run is roughly 6.2 miles, and 100 km/h is close to 62 mph.
• Millilitres to fluid ounces: a US fluid ounce is about 29.6 ml, so a 500 ml bottle holds close to 17 US fl oz.

The quick-conversion buttons above the converter load several of these popular pairs in a single click, and the swap button flips the two units so you can read the conversion in the opposite direction without re-typing anything.

Metric and Imperial: A Quick Background

The metric system (more formally the International System of Units) is built around powers of ten, which is why converting within it is so painless: a kilometre is exactly 1,000 metres, a metre is 100 centimetres, and a litre is 1,000 millilitres. Most of the world uses it for daily life. The imperial and closely related US customary systems grew out of older traditional measures and use less tidy relationships, such as 12 inches to a foot, 3 feet to a yard and 16 ounces to a pound. The two systems are still mixed together constantly: a country can sell petrol by the litre while measuring journeys in miles. This tool simply keeps the exact conversion factors on hand so you never have to remember whether a mile is 1.6 kilometres or the other way around.

Accuracy and Rounding

The converter stores precise conversion factors and does the maths at full floating-point precision, then rounds the displayed answer for readability. Very small results switch to scientific notation and very large ones to a compact format, so the number on screen stays legible. For everyday tasks the displayed figure is more than precise enough. If you are doing something where the last decimal place matters, such as engineering tolerances, medical dosing or financial calculations, treat the result as a strong starting point and confirm against an authoritative reference, because a rounded value is not the same as an exact one. Temperature is handled by formula rather than a single multiplier, since the Celsius and Fahrenheit scales have different zero points as well as different step sizes.

Tips for Getting It Right

• Check the direction: it is easy to convert the wrong way. If a number looks ten times too big or too small, you may have the input and output units reversed. The swap button fixes that instantly.
• Mind US versus UK gallons: they differ by about 20 percent, so always pick the right one for your recipe or fuel figure.
• Watch digital units: storage here uses 1024-based steps, which is why a drive sold as 1 terabyte can appear smaller once your operating system reports it.
• Estimate first: a rough mental approximation (miles are a bit more than 1.5 km, a kilo is a bit over 2 pounds) helps you spot a typo before you rely on the result.

How It Works in Your Browser

This converter is a single self-contained page. The conversion factors, the temperature formulas and the formatting all run as JavaScript on your own device the moment the page loads. Nothing you type is uploaded, and there is no server doing the calculation for you. Your recent conversions are kept only in your browser's local storage so you can glance back at them, and you can wipe that list at any time with the Clear History button. Because everything runs locally, the tool stays instant and keeps working even if your connection drops, and no record of what you converted is ever shared with Quick Merge or anyone else.