How to use a protractor
- Put the centre cross exactly on the vertex (corner) of the angle.
- Line up the baseline (the long straight line through the centre) with one arm of the angle.
- Read where the other arm crosses the scale. Use the scale that starts at 0 on the arm you lined up. That is the outer black numbers when the arm points left, and the inner coloured numbers when it points right.
The faint guide lines every 10° help you draw angles. Mark the centre and the degree point on your paper, then join them with a straight edge.
Making it last
Print on card stock or glue the sheet to thin card before cutting. To see the lines underneath, print on transparency film made for your printer type (inkjet or laser). The 360° protractor is useful for bearings, pie charts and circular crafts. Push a pin through its centre mark to use it as a dial.
Angles at a glance
| Angle | Name | Example |
|---|---|---|
| Less than 90° | Acute | The tip of a pizza slice |
| 90° | Right angle | The corner of a page |
| 90° to 180° | Obtuse | An open laptop |
| 180° | Straight | A flat line |
| More than 180° | Reflex | Use the 360° protractor |
Frequently asked questions
Why does the protractor have two rows of numbers?
So you can measure from either side. The outer scale reads 0° on the left and the inner scale reads 0° on the right. Always use the scale that starts at 0 on the arm you lined up with the baseline.
How big is the printed protractor?
On Letter and A4 the 180° protractor has a radius of about 8.8 cm (a diameter of about 17.6 cm), which is larger than most school protractors and easier to read. The base has a centimetre scale measured from the centre.
My printout is slightly too small. What went wrong?
Almost always the print window was set to "Fit to page", "Fit to printable area" or "Shrink oversized pages", which shrinks the page by 3–6%. Print again with Scale 100% or Actual size. See how to print at actual size for every browser.
Last reviewed 2026-10-07.