We use a scale to measure how heavy something is.
Size isn't only about how long something is — it can be about weight too. We stand on a scale, and it shows our weight in numbers called kilograms.
More facts about Measuring Size
A ruler helps us measure how long or tall something is.
We measure how tall you are in centimetres and metres.
One metre is about as long as a big step or a baseball bat.
Long ago, people measured things using their own feet and hands.
The tallest tree is so big you'd need a very long tape to measure it.