Pitched Roof Area
A pitched roof covers more surface than its plan view. Multiply by the hypotenuse ratio implied by the slope to get the real area.
Your numbers
Roof area
104.4m²
Result
1.044×
Angle (°)
16.7°
Formula
Roof area = Area × √(1 + (Grade (%) ÷ 100)²)
At a 30% pitch the roof is 1.044× the footprint. Eave overhangs must be added separately.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Area (m²)The space a shape covers — length squared. | 100 | 0 and up |
| Grade (%) (%)How far you rise over 100 of horizontal run. | 30 | 0 ~ 200 |
Step by step
Quick reference table
Results when only Area (m²) changes and everything else stays put.
| Area (m²) | Roof area (m²) | Result (×) | Angle (°) (°) |
|---|---|---|---|
| 50 | 52.2 | 1.044 | 16.7 |
| 75 | 78.3 | 1.044 | 16.7 |
| 100 | 104.4 | 1.044 | 16.7 |
| 150 | 156.6 | 1.044 | 16.7 |
| 200 | 208.81 | 1.044 | 16.7 |
What each result means
| Result | At default values |
|---|---|
| Roof area (m²)The roof’s horizontal plan area, seen from above. | 104.4 |
| Result (×)What the formula gives back — the answer this page is for. | 1.044 |
| Angle (°) (°)An angle in degrees; a full turn is 360°. | 16.7 |
Common mistakes
At a 30% pitch the roof is 1.044× the footprint. Eave overhangs must be added separately.
Glossary
- Area
- The space a shape covers — length squared.
- Grade (%)
- How far you rise over 100 of horizontal run.
- Roof area
- The roof’s horizontal plan area, seen from above.
- Result
- What the formula gives back — the answer this page is for.
- Angle (°)
- An angle in degrees; a full turn is 360°.
Frequently asked questions
Q. How is Pitched Roof Area calculated?
Roof area = Area × √(1 + (Grade (%) ÷ 100)²) — A pitched roof covers more surface than its plan view. Multiply by the hypotenuse ratio implied by the slope to get the real area.
Q. Can you walk through an example?
With Area 100m², Grade (%) 30%, the answer is Roof area 104.4m².
Q. What do I need to enter?
Enter Area, Grade (%). 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 Area (m²) moves the answer to Area (m²) 50 → Roof area (m²) 52.2 and Area (m²) 200 → Roof area (m²) 208.81. 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?
At a 30% pitch the roof is 1.044× the footprint. Eave overhangs must be added separately.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.