Roof Pitch Angle
The arctangent of rise divided by run gives the angle. The same ratio times 100 is the percent grade, and the hypotenuse of the two is the rafter length.
Your numbers
Angle (°)
26.57°
Grade (%)
50%
Slant height
670.82cm
Formula
Angle (°) = arctan(Rise ÷ Run), Grade (%) = Rise ÷ Run × 100
That rafter length stops at the wall — add whatever overhang you want at the eaves before cutting.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Rise (cm)How far it climbs, straight up. | 300 | 0 and up |
| Run (cm)How far it travels horizontally. | 600 | 0 and up |
Step by step
Quick reference table
Results when only Rise (cm) changes and everything else stays put.
| Rise (cm) | Angle (°) (°) | Grade (%) (%) | Slant height (cm) |
|---|---|---|---|
| 150 | 14.04 | 25 | 618.47 |
| 225 | 20.56 | 37.5 | 640.8 |
| 300 | 26.57 | 50 | 670.82 |
| 450 | 36.87 | 75 | 750 |
| 600 | 45 | 100 | 848.53 |
What each result means
| Result | At default values |
|---|---|
| Angle (°) (°)An angle in degrees; a full turn is 360°. | 26.57 |
| Grade (%) (%)How far you rise over 100 of horizontal run. | 50 |
| Slant height (cm)The sloped length from apex to base edge — longer than the height. | 670.82 |
Common mistakes
That rafter length stops at the wall — add whatever overhang you want at the eaves before cutting.
Glossary
- Rise
- How far it climbs, straight up.
- Run
- How far it travels horizontally.
- Angle (°)
- An angle in degrees; a full turn is 360°.
- Grade (%)
- How far you rise over 100 of horizontal run.
- Slant height
- The sloped length from apex to base edge — longer than the height.
Frequently asked questions
Q. How is Roof Pitch Angle calculated?
Angle (°) = arctan(Rise ÷ Run), Grade (%) = Rise ÷ Run × 100 — The arctangent of rise divided by run gives the angle. The same ratio times 100 is the percent grade, and the hypotenuse of the two is the rafter length.
Q. Can you walk through an example?
With Rise 300cm, Run 600cm, the answer is Angle (°) 26.57°.
Q. What do I need to enter?
Enter Rise, Run. 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 Rise (cm) moves the answer to Rise (cm) 150 → Angle (°) (°) 14.04 and Rise (cm) 600 → Angle (°) (°) 45. 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?
That rafter length stops at the wall — add whatever overhang you want at the eaves before cutting.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.