Unit conversion is the process of converting a quantity from one system of measurement to another while preserving the underlying value. It’s a common mathematical operation used in various fields, including science, engineering, physics, everyday life and international trade, where different countries may use different units of measurement.

Unit conversion is essential when dealing with measurements in different systems or when you need to express a quantity in a more convenient or appropriate unit.

Converting between units often involves multiplying the original value by a conversion factor, which is a ratio of the two units.

Here are some common unit conversions in different measurement categories:

Length:
1 meter (m) = 100 centimeters (cm)
1 meter = 1,000 millimeters (mm)
1 kilometer (km) = 1,000 meters
1 inch (in) = 2.54 centimetres
1 foot (ft) = 12 inches
1 mile (mi) = 1.60934 kilometres

Mass:
1 kilogram (kg) = 1,000 grams (g)
1 gram = 1,000 milligrams (mg)
1 pound (lb) = 0.453592 kilograms
1 ounce (oz) = 28.3495 grams

Volume:
1 litre (L) = 1,000 millilitres (mL)
1 litre ≈ 0.264172 gallons (US)
1 cubic meter (m³) = 1,000 litre

Temperature:
°C to °F: (°C * 9/5) + 32
°F to °C: (°F – 32) * 5/9
°C to K (Kelvin): K = °C + 273.15

Area:
1 square meter (m²) = 10,000 square centimetres (cm²)
1 square kilometre (km²) = 1,000,000 square meters
1 square foot = 0.092903 square meters
1 acre = 4046.86 square meters

Pressure:
1 psi (pound per square inch) = 6894.76 pascals (Pa)
1 atmosphere (atm) = 101.325 kilopascals (kPa)
1 Pascal (Pa) = 1 Newton per square meter (N/m²)

Time:
1 minute = 60 seconds(s)
1 hour = 60 minutes
1 day = 24 hours

Energy:
1 joule (J) = 1 newton-meter (N·m)
1 calorie (cal) = 4.184 joules
1 kilocalorie (kcal) = 1 Calorie (with a capital “C”) = 4184 joules

Power:
1 watt (W) = 1 joule per second (J/s)

To perform unit conversions, you can use conversion factors and simple arithmetic operations. For example, to convert 10 miles to kilometres, you can use the conversion factor:

1 mile = 1.60934
kilometres 1 mile = 1.60934 kilometres

So, to convert:
10 miles = 10 × 1.60934 kilometres ≈ 16.0934 kilometres

When converting between units, the appropriate conversion factor and formula for the specific measurement must be used. It’s also essential to pay attention to the precision of the measurements, as rounding errors can occur during conversions.

There are many other units and conversions depending on the specific application, you will need to use unit conversion tools for more complex conversions.