Estimate how much roofing material a simple gable or hip roof needs. Measure the building footprint including the overhangs, choose the pitch, and the calculator works out the sloped roof area, the number of roofing squares and how many bundles of shingles to buy.
Formula
Roof area = Footprint × √(1 + (Pitch ÷ 12)²)
Roofers measure in squares of 100 ft². Most asphalt shingles come 3 bundles to a square. Complex roofs with valleys, dormers and hips need more waste — 15% or more.
Worked example
A 40 × 30 ft footprint (1,200 ft²) with a 6/12 pitch has 1,200 × 1.118 = 1,342 ft² of roof. With 10% waste that is 1,476 ft² — 14.76 squares, or 45 bundles of shingles.
Frequently asked questions
How many bundles of shingles are in a square?
Usually three for standard 3-tab and most architectural shingles; some heavy designer shingles need four or five. Check the wrapper.
Does this include starter strips, ridge caps and underlayment?
No. Add starter shingles along the eaves and ridge-cap shingles along ridges and hips; underlayment is sold by the roll.
Last updated · Calculations checked by automated tests· Editorial policy