Roof Area Calculator

Turn the outside dimensions of a building and its pitch into true roof square footage, without climbing a ladder.

Roof area from footprint and pitch

How it works

Footprint = (length + 2 × overhang) × (width + 2 × overhang) Roof area = footprint × √(pitch² + 144) ÷ 12

Every plane of a roof with one pitch is tilted by the same angle, so the whole roof is the footprint stretched by the same factor. That is why a hip roof and a gable roof on the same rectangle, at the same pitch, have identical area. What differs is the edge work: hips need more ridge cap and produce more cutting waste. For L-shapes, add each rectangle's footprint (do not double-count the overlap), or use the multi-section calculator.

Worked examples

Gable ranch. 50 × 30 ft, 1 ft overhangs, 6/12: 52 × 32 = 1,664 sq ft footprint × 1.118 = 1,860 sq ft (18.6 squares).

Hip roof, same house at 8/12. 1,664 × 1.2019 = 2,000 sq ft (20.0 squares). Same footprint, steeper pitch, 140 sq ft more roof.

L-shaped house. Main block 40 × 28 ft and a wing 20 ft wide that sticks out 16 ft from the main wall, 1 ft overhangs, 5/12. Main footprint: 42 × 30 = 1,260 sq ft. The wing is 22 ft wide with its side overhangs, and the main roof’s overhang already covers its first foot, so it adds 22 × 16 = 352 sq ft. Total 1,612 × 1.0833 = 1,746 sq ft.

Roof area for common house sizes

Roof square footage by footprint and pitch
Footprint incl. overhang	4/12	6/12	8/12	10/12	12/12
1,200 sq ft	1,265	1,342	1,442	1,562	1,697
1,600 sq ft	1,687	1,789	1,923	2,083	2,263
2,000 sq ft	2,108	2,236	2,404	2,603	2,828
2,400 sq ft	2,530	2,683	2,884	3,124	3,394
3,000 sq ft	3,162	3,354	3,606	3,905	4,243

Next steps: convert to squares, add waste, then run the shingle takeoff or metal panel calculator.

Frequently asked questions

How do I calculate the square footage of a roof?

Multiply the footprint (length × width, including overhangs) by the pitch multiplier. For a 6/12 roof the multiplier is 1.118.

Is roof area the same as house square footage?

No. Living area counts every floor and excludes overhangs; roof area depends on the footprint, the overhangs and the pitch. A two-story house has far less roof than a ranch with the same living area.

Does a hip roof have more area than a gable roof?

Not at the same pitch over the same footprint. The areas are equal; hip roofs need more ridge cap and have more cutting waste.

Last reviewed 2026-10-10. Results are estimates for planning; confirm quantities with your supplier and requirements with your local building code and the manufacturer's instructions.