Shingle Calculator

Shingle formula

Squares = Roof area (sq ft) / 100 x (1 + waste %)
Bundles = Squares x bundles per square, rounded up
Ridge cap bundles = Ridge and hip length / 33 ft per bundle
Nails = Squares (before waste) x nails per square  (about 140 nails per lb)

Worked example

A 2,600 sq ft hip roof with 15% waste: 2,600 / 100 = 26 squares, x 1.15 = 29.9 squares. At 3 bundles per square that is 89.7, so buy 90 bundles.

Accessories: 65 ft of ridge and hips / 33 = 1.97, so 2 bundles of ridge cap. 150 ft of eave and rake / 105 = 1.43, so 2 bundles of starter strip. Nails: 26 squares x 320 = 8,320 nails / 140 = 59.4 lb, so twelve 5 lb boxes.

Quick reference

How to calculate shingles from roof area

Start with the sloped roof surface area. If you only have ground measurements, multiply the footprint (including overhangs) by the pitch factor first. Divide the area by 100 to get squares, add 10 percent waste for a simple gable roof or 15 to 20 percent for hips and valleys, then multiply by the bundles per square printed on the wrapper, usually 3.

Shingles are sold by the bundle, and suppliers will take back unopened bundles, so round up. A short roof means a second trip and a color lot that may not match, which is a much bigger problem than two extra bundles.

Ridge cap, starter strip and nails

Every ridge and hip gets cap shingles. Pre-cut hip and ridge bundles cover about 33 linear feet; cutting caps from 3-tab shingles gives about 35 feet per bundle. Starter strip goes along every eave and rake edge, and a bundle covers about 105 linear feet. Do not use the main shingles as starter unless the manufacturer allows it, since the sealant strip will be in the wrong place.

Plan on 320 nails per square for standard 4-nail fastening, or 480 in high wind zones. A 1-1/4 inch roofing nail runs about 140 to the pound, so a 20 square roof uses about 46 pounds. Also budget drip edge for every eave and rake, ice and water shield for eaves and valleys, and underlayment for the whole deck.

Key facts

• One roofing square is 100 sq ft, and standard shingles are packed 3 bundles per square, about 33.3 sq ft per bundle.
• A bundle of architectural shingles weighs 65 to 80 lb, so a 20 square roof adds roughly 2 tons to the truck.
• Standard fastening is 4 nails per shingle; high wind areas and steep slopes use 6, raising nail count by 50%.
• Roofing nails should be 12 gauge with a 3/8 in head, long enough to penetrate 3/4 in into the deck: 1-1/4 in for a single layer over sheathing.
• A bundle of hip and ridge cap shingles covers about 33 linear ft, and a bundle of starter strip covers about 105 linear ft.

Frequently asked questions

Sources and references

• •Timberline HDZ shingles product page (GAF)
• •TruDefinition Duration shingles product page (Owens Corning)
• •Nail Application of Asphalt Strip Shingles technical bulletin (Asphalt Roofing Manufacturers Association)
• •Chapter 9 Roof Assemblies, 2021 IRC (ICC)