How many shingles do I need?

Work from roof surface area to whole bundles using the selected product’s coverage.

For 1,500 ft² of roof surface plus 10% extra, covering 1,650 ft² at 100/3 ft² per bundle requires 50 whole bundles.

Measure the surface, not the floor plan

Roof surface includes slope and overhangs. If starting with a horizontal footprint, apply the pitch multiplier first. If you already have measured surface area, do not apply the multiplier again. Use separate calculations for different pitches.

Add an allowance that fits the layout

Valleys, hips, starter needs and cut patterns can affect the order. The calculator’s allowance is editable; ask the installer for the appropriate value. Ridge and starter products often have separate linear coverage and should be listed separately.

Divide by actual bundle coverage

Use coverage from the chosen shingle’s product documents. Divide the adjusted surface area by that coverage and round up once. The example one-third-square bundle is not a rule for every shingle.

Keep the complete roof scope separate

The shingle calculator estimates field shingles only. The roofing calculator adds starter strip, ridge cap, underlayment and drip edge from your roof edges. Flashing, vents, fasteners, ice barriers and roof structure are outside both counts. Product instructions and project-specific requirements control those choices.

Bundles by roof size

For shingles packed three bundles per square (about 33.3 ft² per bundle), with a 10% allowance. These are roof surface areas, not floor areas.

Roof surface	Squares with 10%	Bundles
1,000 ft²	11.0	33
1,500 ft²	16.5	50
2,000 ft²	22.0	66
2,500 ft²	27.5	83
3,000 ft²	33.0	99

If your 2,000 ft² is the house’s footprint rather than its roof, multiply by the pitch multiplier first. At 6:12 that becomes 2,236 ft² of roof surface and 74 bundles. Products packed four or five bundles per square need proportionally more bundles.

Example: starting from the footprint

A 40 × 30-foot footprint (including overhangs) with a 6:12 pitch has about 1,341.64 ft² of roof surface. With 10% extra, that is 1,475.80 ft², or 14.76 squares. At three bundles per square, 44.27 bundles round up to 45. The roofing calculator applies the pitch multiplier for you.

Pitch	Surface multiplier
4:12	1.054
6:12	1.118
8:12	1.202
10:12	1.302
12:12	1.414

Multiply the horizontal footprint by the multiplier for its pitch. Use the roof pitch calculator if you know the rise and run but not the ratio.

Product reference: Owens Corning roofing product documents. Confirm the current label for your chosen product.

Make it your project

Change the measurements and allowance to match your plan.

Open Shingle Calculator

MaterialScope editorial · Updated October 21, 2026 · Calculation methodology