Tools

Roof area calculator, from a plan and a pitch.

The sum is plan length times plan width, divided by the cosine of the pitch. Lengths are in metres. The area is a reference before you ask a roofer for a price.

Published 13 October 2026.

Use the calculator Roofing lists

Calculate the area

Metres, along the eaves, including overhang at the verges.

Metres, wall to wall across the span, including eaves overhang.

Degrees from horizontal. A common house roof is about 30 to 40. Use 0 for a flat roof.

Added to the sloped area. Leave it at no extra if you only want the slope.

Area

The area appears here. Nothing you type is uploaded.

Assumptions, units and limits

Measure the roof in plan, including any overhang past the walls. One rectangle and one pitch. Use 0 degrees for a flat roof. The sloped area then matches the plan. A rectangular plan with one pitch has the same area for a simple gable and a simple hip.

A plan of 10 metres by 6 metres at 35 degrees has a plan area of 60 square metres and a sloped area of 73.2 square metres.

  • Each side is limited to 80 metres, and the pitch to 60 degrees.
  • A dormer, a valley, a chimney or a second pitch is outside this rectangle.
  • The cutting allowance adds 10% or 15% for offcuts. It is still an area, not a tile count and not a price.
  • Lengths are in metres. The same arithmetic describes a roof in metres anywhere. The Malta directory is a separate list, in euro.
Multiplier rounded to three decimal places. The calculator divides by the unrounded cosine.
Pitch Multiplier
0° flat1.000
15°1.035
22.5°1.082
30°1.155
35°1.221
40°1.305
45°1.414
50°1.556

Ask a roofer for the price

Open a roofing list for London, Manchester, Birmingham, Leeds or Bristol and phone the business yourself. There is no account. This site does not pass the job on, and it does not promise a reply. The area is not a price from Local Trades UK.

A qualification is shown on a listing only when that record already has it. This site does not award it and does not guarantee the work.

Questions about this area

Does this page upload the measurements?

No. The sum runs in the browser. The length, width and pitch you type stay on this device.

Is the area a quote for the roof?

No. The result is an area in square metres. The price comes from the roofer you contact. A published band for a new covering, with its source and date, is on the roof cost page.

Can I use this for a hip roof?

A rectangular plan with one pitch uses the same area for a gable roof and a hip roof. A dormer, a valley, a split pitch or a second roof is not included.