Measuring length and height (age 5+)

You have lined up ends to compare lengths. To measure, place same-size cubes in one straight row beside an object. Match the row's ends to the object's ends. The cubes must touch, with no gaps or overlaps. Count them to find the length. For height, measure from the bottom to the top.

Write the number, then its unit: 10 cubes or 2 cm. The number tells how many units. The unit tells what you used. The letters cm mean centimetres. Count only the measuring row. Leave out spare cubes beside it.

Use a centimetre ruler to measure in centimetres. Each space between neighbouring centimetre marks is 1 cm long. Line up one end with 0, which may be inside the ruler's edge. Read the number at the other end. Here the dots mark a strip's ends at 0 and 3. It is 3 cm long.

A gap leaves some length unmeasured. Overlapping cubes cover some length twice. In this model, each box is one cube-wide space. A box marked gap is empty. Fill the gap, then count all the spaces to find how many cubes make a full row.

Unit size changes a count. For the same object, bigger cubes cover more length each, so fewer are needed. If two objects each need the same number of cubes, the one measured with bigger cubes is longer.

A centimetre has a fixed length. Rulers can be different lengths, but 1 cm is the same length on each accurate centimetre ruler. Compare lengths using centimetres or same-size cubes.

You can also count the 1 cm spaces between an object's ends, even away from zero. Here the dots mark ends at 1 and 4. Count three spaces. The strip is 3 cm long.