HowMuchIt / Roofing
How many shingles do I need?
Shingles are counted in squares: 100 square feet of roof. Most come three bundles to a square. You can find the roof's area from the ground, with a tape measure and the roof's pitch.
Work out your shingles
| Pitch | Multiply the footprint by | 1,000 sq ft footprint becomes |
|---|---|---|
| 4/12 | 1.054 | 1,054 sq ft |
| 6/12 | 1.118 | 1,118 sq ft |
| 8/12 | 1.202 | 1,202 sq ft |
| 12/12 | 1.414 | 1,414 sq ft |
1 square = 100 sq ft = usually 3 bundles. Starter and caps use the low end of what one bundle covers (105 and 25 linear ft), so the count errs on the safe side.
Measure a roof without climbing it
Measure the house on the ground, out to the edge of the overhangs, and multiply length by width: that is the roof's flat footprint. A sloped roof is bigger than its footprint, so multiply by the pitch factor: 1.118 for a 6/12 roof, which rises 6 inches for every 12 inches across. Pitch is often on the house plans; a roofer or a phone level app on a rafter in the attic gives it too. If you already know the roof area from a past job or a quote, type it instead.
Waste, starter and caps
A plain roof with two slopes wastes ten to fifteen percent in cuts. Hips, valleys and dormers mean more cuts, so plan fifteen to twenty percent. The first course at the eaves and rakes uses starter strip, and the hips and ridges use cap shingles: both are bought apart from the field shingles, counted by the length of those edges. Check the wrapper of your shingle: some heavy designer shingles take four or five bundles per square, not three.
Questions people ask
How many bundles are in a square?
Three for most 3-tab and architectural shingles, so one bundle covers about 33 square feet. Heavier designer shingles can take four or five.
How many bundles for a 20 x 20 garage roof?
A 20 by 20 footprint is 400 square feet. At a 6/12 pitch that is about 447 square feet of roof, or 4.5 squares; with fifteen percent extra, about 5.1 squares, or 16 bundles. Type 20 and 20 to check yours.
How many nails per shingle?
Four in the standard pattern; six in high-wind areas, and some wind warranties ask for six.
What about underlayment?
Big-brand synthetic rolls are 48 inches by 250 feet, 10 squares before the overlaps. The overlaps eat part of that, so go by the coverage printed on the roll.
Good to know
- A roofing square is 100 square feet of roof surface, a 10 ft by 10 ft area.1,2,3,4
- Most standard 3-tab and architectural asphalt shingles come 3 bundles to a square, so one bundle covers about 33 square feet.1,2,3
- Some heavier or designer shingles take 4 or 5 bundles per square (GAF Woodland: 4, Owens Corning Berkshire: 5), so use the bundles-per-square figure on the wrapper.1,3,5,6
- Multiply the flat (plan) area by the pitch factor to get real roof area: 4/12 = 1.054, 6/12 = 1.118, 8/12 = 1.202, 12/12 = 1.414.2,4,6,7
- From the ground: measure the house footprint out to the edge of the overhangs, then multiply by the pitch factor.4,6,7
- Add about 10 to 15 percent extra shingles for cutting waste on an ordinary roof.1,2,6
- Roofs cut up by hips, valleys and dormers need a bigger allowance, about 15 to 20 percent.2,4
- Starter strip and hip/ridge caps are counted apart from the field shingles: starter by the length of the eaves and rakes, caps by the length of the hips and ridges.3,8,9,10
- A bundle of starter strip covers about 105 to 120 linear feet and a bundle of hip and ridge caps about 25 to 33 linear feet, depending on the brand.8,9,10,11
- Big-brand synthetic underlayment rolls are 48 in by 250 ft, 10 squares before laps; overlaps cut what a roll really covers, so use the coverage printed on the roll.12,13
- Use 4 nails per shingle as the standard pattern; high-wind areas (and some wind warranties) call for 6.14,15,16,17
How we checked this page
Checked on October 27, 2026. We kept a fact only when two independent publishers agree, and each one is numbered to its sources below. Where sources give different numbers, we keep only what they share. We never write a price. This page was written with an AI assistant and checked against the sources below.
Sources
- How Many Bundles of Shingles Are in a Square?, GAF
- Roof Shingles Calculator: How To Find the Right Amount, This Old House
- How to Estimate Materials for Roofing Projects, Fine Homebuilding
- How to calculate roofing squares - pitch multiplier, area, waste, Vertigraph
- Berkshire Shingles (technical data sheet PDF), Owens Corning
- Roofing Area and Shingle Calculator, HomeAdvisor
- Roof Slope Multiplier, InterNACHI
- Pro-Start Starter Strip Shingles, GAF
- Starter Strip Plus Shingle (data sheet PDF), Owens Corning
- All About Hip and Ridge Cap Shingles, GAF
- ProEdge Hip and Ridge Shingle (data sheet PDF), Owens Corning
- Deck Defense High Performance Roof Underlayment (TDS PDF), Owens Corning
- Deck-Armor Premium Breathable Roof Deck Protection (sell sheet PDF), GAF
- Shingle Nails: How to Increase Speed without Losing Accuracy, GAF
- Proper Nailing for Laminated Shingles (product bulletin), IKO
- 9 Upgrades to Windproof Your Roof, Fine Homebuilding
- How many nails do you need per shingle?, RoofersCoffeeShop