Roof Area Calculator

Roof shape and dimensions
Gable Pyramid Hip Hip Single-Slope

Calculations

INPUT DATA

Dimensions

m
m
m
m
m
m

RESULTS

Slope

°
°

Slope lengths

m
m
m
m

Eaves, gables, ridge, hips

m
m
m
m

Roof area

m²
Calculation method → (how the result is obtained) Ask a question
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About Roof Area Calculation

The results are approximate. Before use, verify the calculations against the applicable standards and consult a specialist. The developer is not responsible for the consequences of use without project verification.

This roof area calculator estimates total roof surface in m² for Gable, Hip, Pyramid Hip, and Single-Slope roofs. Enter the building length B, width A, vertical height H, overhangs d1 and d2, and—only for a Hip roof—the offset C. The tool also returns slope angles (°), slope lengths (m), linear totals for eaves, gables/rakes, ridge and hips, and the final roof area with overhangs included.

All inputs and results use the metric system. Values update instantly as you type, so you can test different roof geometries or check how changes in pitch affect the roofing area.

Tips and Tricks

  • What to measure. Measure A (building width) and B (building length) from outer wall to outer wall. Measure H as the vertical rise to the ridge (for single-slope: the vertical rise between the low and high walls). Overhangs d1 and d2 are the horizontal eaves/rake projections beyond the walls.
  • Hip roof parameter C. For a Hip roof, C is the offset from each end of the building to the start of the hip. Larger C means a longer central ridge and shorter hips; the calculator uses C automatically when finding ridge and hip lengths.
  • Typical practical ranges. Overhangs are often 0.20-0.60 m. Common roof slopes: lightweight metal or bitumen sheets 5-15°, profiled metal 10-20°, clay/concrete tiles 22-35°, natural slate 25-40°. Always check the product's minimum slope.
  • Quick geometry hints. On a gable roof, the half-span is A/2 and the rafter (slope) length is √((A/2)² + H²). For a single-slope roof, use √(A² + H²). The calculator applies these relations and adds overhangs to get true surface area.
  • Material allowance. After you get the area, add waste: typically 5-12% for simple gables, 10-15% for hips and complex roofs. Small-format tiles, valleys, or many penetrations may require more.
  • Split complex roofs. For L-shapes or additions, calculate each block separately (choosing the correct type per block) and sum the areas.
  • Safety & norms. When choosing slopes and details, consult relevant European standards such as EN 1991-1-3 (snow loads) and EN 1991-1-4 (wind actions), plus the roofing manufacturer's guidance.

FAQs

How do I calculate roof area with pitch (slope)?

Enter A, B, and the vertical rise H. The calculator converts pitch to rafter (slope) lengths using right-triangle geometry, then multiplies by the plan dimensions and adds the overhangs. This gives an accurate calculate roof area result even for steep roofs.

Which measurements do I need for this area of a roof calculator?

You need building length B, width A, height H, and overhangs d1 and d2. If you choose a Hip roof, also provide the offset C. Results include slope angles, slope lengths, eaves, gables/rakes, ridge, hips, and total roof surface area in m².

What is the roof area calculation formula used here?

The core idea is: area of each plane = slope length × plan dimension, with overhangs added to both directions. For example, a gable roof uses 2 × (rafter length along A + d1) × (B + 2·d2), where rafter length = √((A/2)² + H²). The calculator applies the proper formula for each selected roof type.

How do I use the hip roof area calculator correctly?

Select Hip, enter A, B, H, d1, d2, and the offset C. The tool derives the ridge length (shorter when C is larger) and the hip lengths, then computes the roof surface. For a pyramid hip (no ridge), choose Pyramid Hip and leave C hidden.

How accurate is the result and what tolerance should I use?

For rectangular roofs with good measurements, the computed roof surface area is typically within a few percent of reality. Add an installation allowance (see tips above) and round up to full packages according to the roofing product you plan to use.