Start with your roof's total square footage

The first step is measuring the actual surface area of your roof, not the footprint of your house. A roof with a steep pitch covers more area than a flat roof on the same building. Measure the length and width of each roof plane (the flat sections), then multiply length by width. If your roof has four planes, calculate each one separately and add them together.

If you cannot safely access your roof, you can estimate from the ground. Measure the length and width of your house, multiply them, then multiply that number by a pitch factor. For a roof with a 4:12 pitch (4 inches of rise for every 12 inches of horizontal run), multiply by 1.054. For a 6:12 pitch, multiply by 1.118. For a 8:12 pitch, multiply by 1.202. A steeper roof needs a higher multiplier. If you do not know your pitch, a roofer can tell you in minutes, or you can climb a ladder and measure 12 inches horizontally along the roof edge, then measure how many inches it rises — that rise number is your pitch.

Key Takeaways

  • Roof shingles are sold by the "square," which covers 100 square feet, so divide your total roof area by 100 to find how many squares you need.
  • Add 10 percent to your calculated total to account for waste, overlap, and mistakes during installation.
  • One bundle of shingles typically covers about 33 square feet, so each square requires roughly three bundles.
  • Shingle color, weight, and warranty vary widely, so compare products before ordering to avoid buying the wrong type for your climate or budget.
  • Order all shingles at once from the same production batch so color and texture match across your entire roof.

Convert square footage to roofing squares

Roofing material is sold by the "square," a standard unit meaning 100 square feet of coverage. Divide your total roof area by 100. If your roof is 2,400 square feet, you need 24 squares. If your roof is 2,650 square feet, you need 26.5 squares — round up to 27 squares to avoid running short.

This is where most people make their first mistake: they order exactly what the math says they need. Do not do that. Add 10 percent to account for waste at the edges, mistakes during installation, and future repairs. If you need 24 squares, order 26.4 squares — round up to 27. If you need 27 squares, order 29.7 squares — round up to 30. The extra shingles are cheap compared to a second trip to the supplier or a roof that looks patchy because you ran out mid-project.

Understand how shingles are bundled and priced

Shingles come in bundles, not squares. One bundle typically covers about 33 square feet, though this varies by shingle weight and style. A standard asphalt shingle bundle weighs 50 to 80 pounds. Three bundles make one square (roughly 100 square feet). So if you need 27 squares, you need about 81 bundles.

Bundles are priced individually, so multiply the per-bundle price by the number of bundles you need. A bundle might cost $25 to $50 depending on shingle quality and where you buy. Heavier shingles (rated in pounds per square) cost more but last longer — a 235-pound shingle lasts longer than a 185-pound shingle. Check the weight rating on the package before you buy.

Account for roof complexity and waste

A straightforward rectangular roof wastes less material than a roof with valleys, dormers, or multiple angles. Valleys are the V-shaped seams where two roof planes meet; dormers are the small structures that stick out from the roof. Each valley and dormer requires cutting and fitting shingles, which creates waste. If your roof is straightforward, 10 percent extra is enough. If your roof has multiple valleys or dormers, add 15 percent instead.

Waste also happens at the edges. Shingles along the perimeter often need to be cut to fit. The steeper your roof pitch, the more cutting is involved because shingles must be nailed at specific angles. A very steep roof (10:12 pitch or higher) may need 15 to 20 percent extra to account for cuts and mistakes.

Choose shingle type and check climate compatibility

Asphalt shingles are the most common and affordable. They come in three-tab (flat, uniform appearance) and architectural (textured, dimensional look) styles. Architectural shingles cost more but last longer and look better. Both types come in various colors — black, gray, brown, and blended tones are standard.

Your climate affects which shingles work best. In hot, sunny climates, lighter colors reflect heat and reduce cooling costs. In cold, snowy climates, darker colors absorb heat and help snow slide off. In areas with high wind, you need shingles rated for wind resistance — look for a rating of 90 mph or higher. In areas prone to hail, impact-resistant shingles cost more but survive hail better and may lower your insurance premium. Check your local building code or ask a roofer what your area requires.

Order all shingles from the same production batch

Shingles are manufactured in batches, and color and texture can vary slightly between batches even if the product name is identical. If you order shingles at different times or from different suppliers, some sections of your roof may look noticeably different from others. Order your entire quantity at once from the same supplier if possible, and ask the supplier to confirm all bundles are from the same production run.

Store shingles flat in a cool, dry place before installation. Shingles stored in direct sun or heat can become brittle or warp. If you must store them outside, cover them with a tarp. Do not stack bundles more than four high, as the weight can damage the shingles underneath.

Double-check your order before paying

Before you finalize your purchase, verify the total number of bundles, the shingle type and color, and the price per bundle. Ask the supplier whether the price includes delivery or if delivery is extra. Some suppliers charge a flat delivery fee; others charge by distance or weight. If you are buying from a big-box store, confirm whether they stock the shingles in the color you want or whether they need to order them — some colors have longer lead times.

Keep your receipt and the product information from the shingle packages. If a shingle is defective or the color does not match what you expected, you may need to return it. Most suppliers have a return window of 30 days, though this varies. Damaged bundles should be reported when ready so you can exchange them before installation.

Frequently Asked Questions

What if I measure my roof and get an odd number like 24.7 squares?

Round up to 25 squares, then add 10 percent (2.5 squares), which brings you to 27.5 squares. Round up again to 28 squares. It is better to have leftover shingles than to run short during installation.

Can I use shingles from different brands or colors on the same roof?

Technically yes, but it will be visible. Different brands have different thicknesses and textures, so they will not blend. If you must add shingles later for repairs, try to match the original product and batch number. For a full roof replacement, use one brand and color throughout.

Do I need to buy underlayment or other materials besides shingles?

Yes. You will also need roofing underlayment (a waterproof barrier under the shingles), roofing nails, and flashing (metal pieces that seal valleys and edges). These are usually sold separately. Ask your supplier what else you need for your specific roof type.

What is the difference between a 20-year and a 30-year shingle?

The warranty length, which reflects how long the manufacturer expects the shingles to last under normal conditions. A 30-year shingle is usually thicker and heavier than a 20-year shingle, so it resists weather and UV damage longer. The actual lifespan depends on your climate, roof pitch, and ventilation.

Should I buy extra shingles for future repairs?

Yes, if you have room to store them. Buy one or two extra bundles and keep them in a cool, dry place. Shingles fade over time, so having extras from the original batch means future repairs will match better than shingles bought years later.