Ruler Cm 15 — free printable clipart

How to read a 15 cm ruler

This is a 15 centimetre ruler, numbered from 0 to 15. The numbered marks stand 1 centimetre apart and the small marks between them stand 1 millimetre apart, so the whole scale covers 15 cm — the same length as 150 mm.

Scale

0 cm to 15 cm

Total length

15 cm

Same length in millimetres

150 mm

Numbered marks

16 (0 to 15)

One centimetre

10 mm

Small marks between two numbers

9

• Line the start of what you are measuring up with the 0 mark, not with the end of the ruler. Most rulers leave a small margin of plastic or wood before the scale begins, so starting at that edge sets the object back behind the 0 and the reading comes out too short — by exactly the width of that margin.
• Between any two numbered centimetre marks there are 9 small marks, which divide that centimetre into 10 equal millimetres. So the small marks are counted in millimetres: 3 cm and 4 small marks is 3.4 cm, or 34 mm.
• To change centimetres into millimetres, multiply by 10 — this ruler's 15 cm is 15 × 10 = 150 mm. To go back, divide by 10.
• A length longer than 15 cm will not fit in one go. Measure to the 15 cm mark, make a pencil tick, slide the 0 mark to the tick and carry on, then add the two readings together.
• Read the ruler straight on. Looking at the scale from an angle makes the mark appear to shift against the object, which is a reading error rather than a measuring one.