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addition

Addition with measures

Combine lengths, masses, capacities and times accurately.

Quick answer

You can add lengths, masses, capacities, and times together just like you add numbers – but you must make sure the units are the same first.

Learning outcome

By the end of this page, you will be able to add together measurements of length, mass, capacity, and time using the correct units and showing your working clearly. Success signs:
  • You can add two lengths and get the total in the same unit (like metres and centimetres)
  • You can add masses and get the total in the same unit (like kilograms and grams)
  • You can add capacities and get the total in the same unit (like litres and millilitres)
  • You can add times and get the total in hours and minutes

Why this matters

Adding measures is useful in many everyday situations. When you are cooking, you need to add ingredients together. When you are planning a journey, you add up the distances. When you are shopping, you add up the weights of items. In sports, you add up scores or times. All of these situations involve combining measurements to find a total. Understanding how to add measures helps you solve problems and make decisions in real life.

How it works

To add measures, follow these simple steps:
  1. Identify the units you are working with (e.g., metres, kilograms, litres, minutes)
  2. Make sure all measurements are in the same unit
  3. Add the numbers together
  4. Write your answer with the correct unit
Sometimes, you will need to convert between units. For example, if you are adding 500 grams and 2 kilograms, you need to change 2 kilograms into 2000 grams first. Then you can add 500 + 2000 = 2500 grams.

Examples you can see

Let’s look at some examples of addition with measures. Example 1: Adding lengths You have a ribbon that is 120 centimetres long and another that is 80 centimetres long. How long are they together?
  • 120 cm + 80 cm = 200 cm
Example 2: Adding masses A bag of apples weighs 2 kilograms and a bag of oranges weighs 1 kilogram 500 grams. What is the total weight?
  • First, convert 1 kg 500 g to grams: 1 kg = 1000 g, so 1000 + 500 = 1500 g
  • Then add: 2000 g + 1500 g = 3500 g
  • Convert back to kilograms: 3500 g = 3 kg 500 g
Example 3: Adding capacities You pour 750 millilitres of juice into a bottle and then add another 250 millilitres. How much juice is in the bottle?
  • 750 ml + 250 ml = 1000 ml
  • 1000 ml = 1 litre
Example 4: Adding times You watch a movie that is 1 hour 30 minutes long and then watch another that is 2 hours 15 minutes long. How long do you watch in total?
  • Add hours: 1 + 2 = 3 hours
  • Add minutes: 30 + 15 = 45 minutes
  • Total time = 3 hours 45 minutes

Try it as a mini adventure

Adventure: The Great Garden Plan You are helping your family plan a garden. You have three sections:
  • Section A: 3 metres long and 2 metres wide
  • Section B: 4 metres long and 1 metre wide
  • Section C: 2 metres long and 3 metres wide
You want to find the total length of all the sections together.
  • Section A: 3 m
  • Section B: 4 m
  • Section C: 2 m
Add the lengths together:
  • 3 m + 4 m + 2 m = 9 m
You also want to find the total width of all sections together.
  • Section A: 2 m
  • Section B: 1 m
  • Section C: 3 m
Add the widths together:
  • 2 m + 1 m + 3 m = 6 m
You can now tell your family that the garden sections together are 9 metres long and 6 metres wide.

Common mistakes

  • Mistake: Adding different units without converting first.
    • Why it happens: Children often forget that 1 kg = 1000 g and 1 litre = 1000 ml.
    • Fix: Always check that units are the same before adding. If not, convert them first.
  • Mistake: Forgetting to carry over when adding larger numbers.
    • Why it happens: When adding numbers like 500 + 700, children might not remember to carry the 1 from 1000.
    • Fix: Use column addition and write the carry numbers clearly.
  • Mistake: Not writing the correct unit in the answer.
    • Why it happens: Children focus on the numbers and forget the unit.
    • Fix: Always check that your final answer includes the correct unit.

Parent and carer guide

Parents and carers can help by:
  • Encouraging children to convert units before adding (e.g., 1 kg = 1000 g)
  • Practising with real-life examples like shopping, cooking, or measuring at home
  • Using visual aids like rulers, scales, or measuring jugs to help children understand
  • Checking that children write the correct units in their answers
  • Practising with games or puzzles that involve adding measurements
What to say:
  • “Can you help me add up the weights of these items?”
  • “Let’s see how much time we spend on different activities today.”
  • “What do you notice about the units when you add them?”
What not to worry about:
  • Children may make mistakes at first – this is normal
  • They might not convert units perfectly at first – practice helps
  • They might forget units – gently remind them to include them

Practice questions

  1. Add 3 metres 50 centimetres and 2 metres 75 centimetres.
  2. Add 4 kilograms 200 grams and 1 kilogram 800 grams.
  3. Add 600 millilitres and 400 millilitres.
  4. Add 2 hours 45 minutes and 1 hour 30 minutes.
  5. Add 50 centimetres and 70 centimetres.
Answers:
  1. 5 metres 125 centimetres (or 6 metres 25 centimetres)
  2. 6 kilograms 0 grams (or 6 kilograms)
  3. 1000 millilitres (or 1 litre)
  4. 4 hours 15 minutes
  5. 120 centimetres (or 1 metre 20 centimetres)

FAQ

What is addition with measures?

Addition with measures is adding together different amounts of length, weight, capacity, or time, making sure all units are the same before adding.

Why do we need to convert units?

We convert units so that we are adding the same type of measurement. For example, we can’t add 500 grams and 2 kilograms directly, so we convert 2 kilograms to 2000 grams first.

Can I add metres and centimetres together?

Yes, but you need to convert them to the same unit first. For example, 1 metre 50 centimetres = 150 centimetres.

How do I add times?

Add hours with hours and minutes with minutes. If minutes go over 60, convert the extra minutes to hours.

What are some real-life examples of addition with measures?

Examples include adding ingredients in a recipe, combining distances for a journey, or adding up the weights of items in a shopping basket.