What is a roofing square?

A square is 100 square feet of roof surface — the standard unit roofers and shingle manufacturers use.

How many bundles of shingles per square?

Most architectural shingles come 3 bundles per square. Heavier designer shingles may need 4 or 5.

Why does roof pitch matter?

A steeper pitch increases the actual roof surface beyond the footprint, so more material is required.

How to Measure A Roof

Learn how to measure a roof step by step, with the tools, materials, and a free calculator to estimate exactly what you need. To estimate roofing, multiply your home's footprint (length × width) by a pitch factor, then divide by 100 to get squares. Add 10–15% for waste. Shingles come 3 bundles per square. A 40×30 ft home with a 6:12 roof needs about 14.8 squares and costs roughly $5,900–$10,300 installed.

Get exact numbers

Use the free Roofing Calculator to estimate your project.

Open calculator

Tools

Tape measure
Ladder
Roofing nailer
Chalk line
Utility knife

Materials

Shingles
Underlayment
Drip edge
Ridge cap
Flashing & nails

Step-by-step

1
Measure the footprint
Use the building's length × width at ground level.
2
Apply the pitch factor
A steeper roof has more surface — e.g. 6:12 multiplies area by 1.118.
3
Convert to squares
Divide total roof area by 100. One square = 100 sq ft.
4
Add waste and bundles
Add 10–15%, then multiply squares by 3 for shingle bundles.

Pro tips

Avoid: ignoring roof pitch — Using the footprint alone underestimates a sloped roof's true surface area. Always apply a pitch multiplier.
Avoid: skipping the waste factor — Hips, valleys, and starter/ridge courses create offcuts. Add 10% for simple roofs and 15% for cut-up roofs.
Avoid: forgetting accessories — Underlayment, drip edge, ridge cap, and flashing aren't counted in shingle bundles — budget for them separately.
Avoid: measuring from the ground — Eaves and overhangs extend past the walls. Measure the actual roof plane, not the building's footprint, when you can.