Roof pitch & slope geometry

MEASURE FIRST

How to prepare your inputs

Use professional measurements or drawings. Roof surface area differs from horizontal catchment area; check which the tool needs.

How this calculation works

Angle = atan(rise ÷ run). Slope length = √(rise² + run²). Surface area = slope length × roof length × slope count.

Assumptions & exclusions

Simple rectangular slopes only. Enter dimensions including overhangs if they are to be included. Excludes hips, valleys, dormers and sheet laps. Not a rafter design, cut template or roofing compliance check.

Your next step

Confirm pitch suitability, laps, flashings, access and drainage design with the roofing contractor.

Further reading

• Blocklayer calculator directory

These resources provide background information. Confirm current product specifications and project requirements with your supplier or trade professional.

What if my shape or product is different?

Use dimensions and product data that match the stated method. For complex work, calculate separate sections or obtain a project-specific take-off. Do not apply simple geometry to structural or compliance decisions.

Why are quantities rounded up?

Whole bags, packs, sheets or cartridges round up to purchasable units. Decimal area or volume results are planning figures; confirm order increments with the supplier.

Are my entries saved?

No. Entries remain in the current browser page and clear on reload. Printing can save your results and inputs as a PDF on your device.