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📐 Measuring and Comparing Lengths

Use a ruler the right way, measure in centimetres, learn that 100 cm make 1 metre, and compare the lengths you find.

4
lessons
~20 min
to learn
🔢 Math
subject
Ages 6–12
level
Start the course →

What you’ll learn

  1. Reading a RulerMeasure correctly by lining up the object with the 0 mark and reading the far end.A ruler measures length in centimetres. The key is to line up one end of the object with the 0 mark, keep it straight, and read the number at the other end.
  2. Measuring in CentimetresRead a length in centimetres and record it with the number and the unit cm.The number where an object ends is its length in centimetres. We write the measurement with its unit, like 7 cm, so everyone understands it.
  3. Centimetres and MetresUnderstand that 100 cm make 1 m and swap between centimetres and metres.Metres measure big lengths, and every metre is made of exactly 100 centimetres. That means amounts like 200 cm and 2 m are the same length.
  4. Comparing LengthsCompare, order, and find the difference between measured lengths in the same unit.With lengths measured in the same unit, the bigger number is longer, and several can be ordered shortest to longest. Taking one away from the other tells you how much longer it is.

Questions this course answers

When you measure, which number should one end of the object line up with?

You always start measuring from the 0 mark on the ruler.

A pencil starts at 0 and its tip reaches the 13 mark. How long is it?

The number where the object ends, 13, is its length: 13 cm.

How many centimetres make 1 metre?

There are exactly 100 centimetres in 1 metre.

Which is longer, 1 metre or 50 cm?

1 metre is 100 cm, which is more than 50 cm.

One string is 20 cm and another is 35 cm. Which is longer?

35 is a bigger number than 20, so the 35 cm string is longer.

200 cm is the same as how many metres?

Every 100 cm makes 1 m, so 200 cm is 2 metres.

Grounded in trusted sources

  • Khan Academy Kids
  • BBC Bitesize — KS1 Maths
  • Britannica Kids
  • PBS Kids — early math

Every Wunder lesson is built from real, reputable sources — never invented.

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