Unit Conversion Made Simple: Metric, Imperial and Data Sizes

Metric and imperial in plain terms

The metric system is built on tens: a kilometre is a thousand metres, a metre is a hundred centimetres. Imperial and US customary units, such as inches, feet, miles, pounds and gallons, have irregular relationships, which is why they are harder to convert in your head.

Most of the world uses metric, while the United States still uses customary units in daily life. If you shop, travel or follow recipes internationally, you will meet both.

A converter is most valuable when a mistake is costly: ordering materials, following medicine instructions on a label, or buying the right cable length. In those cases, a quick check beats a confident guess.

Using the Unit Converter

The tool covers length, weight, temperature, volume, area, speed, time and data. Pick a category, enter a value and choose the from and to units.

1. Open the Unit Converter and choose the category.
2. Type the value you want to convert.
3. Select the unit you are starting with.
4. Select the unit you want.
5. Read the result and copy it if needed.

Conversions worth remembering

You do not need to memorise tables, but a few rough anchors help you spot an obviously wrong answer.

Use these anchors as a sanity check only. For anything that needs precision, such as a measurement for building work, use the converter and keep several decimal places until the final step.

• 1 inch is 2.54 centimetres.
• 1 kilogram is about 2.2 pounds.
• 1 mile is about 1.61 kilometres.
• 1 litre is about 1.06 US quarts.
• 1 US gallon is about 3.79 litres.

Temperature is different

Length and weight conversions are multiplications. Temperature is not, because the scales start at different points. To convert Celsius to Fahrenheit, multiply by 9, divide by 5 and add 32. To convert Fahrenheit to Celsius, subtract 32, multiply by 5 and divide by 9.

As a check, 0 degrees Celsius is 32 Fahrenheit and 100 degrees Celsius is 212 Fahrenheit. A converter handles the arithmetic and removes the chance of forgetting the 32.

Data units and the 8-bit trap

Data sizes cause regular confusion. A byte is eight bits. Internet speeds are usually quoted in bits per second, while file sizes are in bytes. A connection of 100 megabits per second therefore downloads roughly 12.5 megabytes each second at best.

There is also a difference between decimal prefixes, where a kilobyte is 1000 bytes, and binary ones, where it is 1024. Different tools and systems use each, so small differences in reported sizes are normal.

A practical scenario

Someone moving abroad finds a flat listed at 65 square metres and wants to compare it with a 700 square foot home. Converting one into the other in the area category shows that 65 square metres is about 700 square feet, so the two are nearly the same size. Without the converter, the comparison would be a guess.

The same habit helps in the kitchen. A butter pack in ounces, a recipe in grams and a tray size in inches can all be handled in a couple of minutes if you convert each value once and write down the results.

Mistakes to avoid

Check that you picked the right category, since volume and weight units look similar but are not interchangeable. Be careful with US versus imperial gallons, and with bits versus bytes. When the result looks surprising, compare it with a rough anchor before you rely on it.

Another frequent slip is rounding too early. If you convert in several steps, keep the full number until the end and round only once.

Frequently asked questions