Measuring length
Maths · Key Stage 1 · The School
Longer, shorter, the same
Lay two pencils side by side. Line them up at one end. The pencil that reaches further is longer. The other is shorter. If both ends match, they are the same length. Always start them at the same place.
Measuring with everyday objects
Lay paperclips end to end along a book. No gaps. No overlaps. Count how many fit. The book is 6 paperclips long. Cubes work too. So do hand-spans and steps. Any same-size thing, laid end to end, can measure.
Why everyone needs the same unit
Two children measure one pencil. One uses big clips and counts 4. One uses small clips and counts 7. The pencil did not change. The clip size changed. So the count changed. This is why we use one fixed unit: the centimetre. Then everyone gets the same number.
Measuring in centimetres
Line the object up with the 0 mark on a ruler. Not the edge — rulers often have a gap before 0. Read the number where the object ends. A pencil that ends at 12, starting from 0, is 12 cm long. Starting from the edge is the top mistake to avoid.
Measuring and ordering three objects
A ruler is 30 cm. A pencil is 14 cm. A rubber is 4 cm. Shortest to longest: rubber, pencil, ruler. Longest to shortest: ruler, pencil, rubber. The numbers do the ordering. You do not need to guess by eye.