Tools · Roofing
Turn roof lengths and pitch into an area range
Measure the plan of the building, not the slope, then add the pitch. The arithmetic stays in this tab.
What the formula assumes
Plan area is length × width. Sloped area is plan area ÷ cos(pitch). A hip roof multiplies that sloped area by 1.12. Cutting allowance then adds the percentage you chose.
The page does not model dormers, valleys, two different pitches, or a chimney stack. Those change a take-off. A 12% hip factor is a first look, not a survey.
Four London roofing cards publish a £1,000 workmanship guarantee. That is a warranty line, not a price per square metre. Read the cost notes before you treat any pound figure as a bill.
Questions about this area
Does this include dormers, valleys or chimneys?
No. It treats a simple rectangle. Dormers, valleys, hips beyond a 12% allowance, and chimney cutting sit outside the figure.
Is the area a materials order?
No. A merchant or roofer still takes off the covering. Use the range on a call, not as a pallet count.
What pitch should I use if I do not know it?
Many tiled UK roofs sit near 35 degrees. If you are unsure, ask the roofer rather than inventing a steep pitch.