Miter Angle Calculator
The outside turn where two pieces meet — the exterior angle — is 360÷n. Each piece takes half of it, so the saw angle is 180÷n, while the interior angle left inside is 180×(n−2)÷n. A square frame is cut at 45° because that is half of a 90° turn.
Your numbers
Angle (°)
45°
Interior angle
90°
Perimeter
200cm
Formula
Angle (°) = 180 ÷ Number of sides
Many miter saws read the angle away from 90° instead. A hexagon needs 30°, which may show as 60° on the scale, so cut a test piece first.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Number of sidesHow many sides the polygon has, counting from three. | 4 | 3 ~ 24 |
| Side length (cm)One side of a regular polygon — they are all the same. | 50 | 0 and up |
Step by step
Quick reference table
Results when only Number of sides changes and everything else stays put.
| Number of sides | Angle (°) (°) | Interior angle (°) | Perimeter (cm) |
|---|---|---|---|
| 3 | 60 | 60 | 150 |
| 4 | 45 | 90 | 200 |
| 6 | 30 | 120 | 300 |
| 8 | 22.5 | 135 | 400 |
What each result means
| Result | At default values |
|---|---|
| Angle (°) (°)An angle in degrees; a full turn is 360°. | 45 |
| Interior angle (°)The interior angle at one corner of a regular polygon. | 90 |
| Perimeter (cm)The total length around the outside of a shape. | 200 |
Common mistakes
Many miter saws read the angle away from 90° instead. A hexagon needs 30°, which may show as 60° on the scale, so cut a test piece first.
Glossary
- Number of sides
- How many sides the polygon has, counting from three.
- Side length
- One side of a regular polygon — they are all the same.
- Angle (°)
- An angle in degrees; a full turn is 360°.
- Interior angle
- The interior angle at one corner of a regular polygon.
- Perimeter
- The total length around the outside of a shape.
Frequently asked questions
Q. How is Miter Angle Calculator calculated?
Angle (°) = 180 ÷ Number of sides — The outside turn where two pieces meet — the exterior angle — is 360÷n. Each piece takes half of it, so the saw angle is 180÷n, while the interior angle left inside is 180×(n−2)÷n. A square frame is cut at 45° because that is half of a 90° turn.
Q. Can you walk through an example?
With Number of sides 4, Side length 50cm, the answer is Angle (°) 45°.
Q. What do I need to enter?
Enter Number of sides, Side length. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Number of sides moves the answer to Number of sides 3 → Angle (°) (°) 60 and Number of sides 8 → Angle (°) (°) 22.5. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Many miter saws read the angle away from 90° instead. A hexagon needs 30°, which may show as 60° on the scale, so cut a test piece first.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.