Ruler Cm 10 Zoom — free printable clipart

How long is the pencil?

The pencil in this picture is 37 millimetres long. Its blunt end is lined up with the 0 mark and its tip reaches the 37 mm mark, so its length is 37 mm — the same as 3.7 cm.

Length

37 mm

Same length in centimetres

3.7 cm

Where it ends

between the 3 cm and 4 cm marks

Read as centimetres and millimetres

3 cm and 7 mm

One centimetre

10 mm

• The pencil starts at 0, so the number its tip reaches IS its length. If it started at another mark you would have to subtract: an object from 2 cm to 5 cm is 3 cm long, not 5.
• To read the length in centimetres, count the whole centimetres first and then the leftover small marks: 3 whole centimetres and 7 millimetres more, which is written 3.7 cm.
• Millimetres change to centimetres by dividing by 10 — 37 ÷ 10 = 3.7 cm — and centimetres change to millimetres by multiplying by 10.
• Measuring in millimetres rather than centimetres is what lets a length be given exactly without a fraction, which is why millimetres are the usual unit for small objects in design and engineering.