How Many Shingles Do I Need? Roofing Squares Explained

Start with roofing squares

Roofers measure in squares, not square feet. One roofing square is 100 square feet of roof surface. Shingles are sold by the bundle, and it takes about 3 bundles of standard architectural shingles to cover one square.

So the whole job is really two steps: find your roof's true area, divide by 100 to get squares, then multiply by 3 for bundles — plus waste.

Try it Roofing Calculator → Estimate roofing squares, shingle bundles and underlayment from your roof footprint and pitch, with waste and rough cost.

Adjust the footprint for pitch

A roof's surface is bigger than the house's footprint because it slopes. Multiply the footprint by a pitch factor: a 4/12 roof is about 1.05×, 6/12 about 1.12×, and a steep 12/12 about 1.41×. A 1,600 sq ft footprint at 6/12 is roughly 1,790 sq ft of roof — about 18 squares.

• Measure the footprint from the ground plan, then apply the pitch factor — don't climb the roof to measure if you can avoid it.
• Steeper roofs cost more in both material and labor.
• Complex roofs with many hips and valleys need more waste.

Add waste, underlayment and accessories

Add 10% waste for a simple gable roof and up to 15% for cut-up roofs with lots of hips and valleys. Don't forget underlayment (one roll covers about 4 squares), starter strip, ridge cap, drip edge and nails — they're separate line items from the field shingles.