Unit Conversions

Unit Conversions

Introductory Concepts

  • Unit conversions play a key role in many real-world applications, including physics, engineering and everyday mathematics. They allow us to convert between different types of measures for the same sort of quantity, such as length or weight.
  • A strong understanding of unit conversions forms part of the foundational knowledge required for success in the ratio, proportion and rates of change section of the mathematics syllabus.

Important Units to Know

  • Familiarise yourself with the metric units of measurement such as kilogram (kg), gram (g), metre (m), centimetre (cm), millimetre (mm), litre (l) and millilitre (ml).
  • Recognise the imperial units like inch, foot, yard, mile, ounce, pound, pint, quart and gallon and their relationships with metric units.
  • Be aware of time units such as seconds, minutes, hours, days, weeks, months and years.

Conversion Factors

  • A conversion factor is a ratio expressing how many of one unit are equal to another unit. For example, 1 km = 1000 m, so the conversion factor from km to m is 1000.
  • Some common conversion factors you need to know are:
    • 1 m = 100 cm
    • 1 km = 1000 m
    • 1 hour = 60 minutes
    • 1 minute = 60 seconds
    • 1 kg = 1000 g
    • 1 l = 1000 ml

Converting Units

  • To convert units, multiply the original number by the appropriate conversion factor.
  • For example, to convert 3 km into metres, we multiply 3 * 1000 to get 3000 m.
  • Conversely, to convert from a larger unit to a smaller unit, we divide.

Units in Calculations

  • When undertaking calculations, it’s crucial to ensure all measurements are in the same units. Convert any measurements to the same unit before calculating.
  • The final answer should be given in the appropriate units. Remember to record units in your answer, as often the units give a clue to the meaning of a result.
  • Always double check your work to ensure your units make sense in the context of a problem.

Conversion Tables

  • Conversion tables can be handy references for converting units. They usually list conversion factors between different units of a certain quantity.
  • Practice using conversion tables to get more comfortable with unit conversions. For example, use one to convert temperatures between Celsius and Fahrenheit, or to convert distances from miles to kilometres.

Handy Tips

  • Practise lots, using real world problems to get comfortable with unit conversions.
  • Don’t hesitate to use a calculator when carrying out unit conversions.
  • Remember that the more frequently you practise, the easier it becomes to recall conversion factors and correctly convert units.