Roofing Shingles Calculator

How this roofing shingles calculator works

Shingles are sold by the bundle but priced and planned by the square. One square covers 100 sq ft of roof. Most asphalt shingles come three bundles to a square, so each bundle covers about 33.3 sq ft. The roofing shingles calculator finds your true roof area, adds waste for cutting, and divides by what one bundle covers.

It then works out everything else a roofer puts on the truck. Those items are ordered by length, not area, so the calculator also needs the length of your eaves, rakes, ridges, hips and valleys. In footprint mode it works those out for you from the house size and roof shape. In the other two modes you type them in from a roof report or a tape measure.

Three steps, in order:

1. Roof area. Footprint plus overhangs, times the pitch multiplier. Or the sum of each roof face you measured. Or a number you already have.
2. Waste. 10% for a plain gable, 15% for a hip roof and 20% for a cut-up roof with valleys and dormers. You can set your own.
3. Materials and price. Bundles, accessories, nails and a cost for each line, using prices you can change.

How many squares of shingles do I need?

Take your roof area in square feet, divide by 100, and add waste. A 1,744 sq ft roof is 17.44 squares. With 10% waste you order about 19.2 squares. That's the number a roofer quotes against and the number a supplier wants.

The hard part is getting the roof area right. A roof is always bigger than the house under it, for two reasons. First, the roof hangs past the walls. Second, the roof is tilted, so it's longer than the flat ground it covers. The pitch multiplier fixes the second part. It's √(1 + (pitch ÷ 12)²). A 6/12 roof has a multiplier of 1.118, so it has 11.8% more surface than its footprint.

Measuring from the ground

1. Measure the length and width of the house at the walls. Include an attached garage if it's under the same roof.
2. Check the overhang at an eave. Measure from the wall to the edge of the fascia. 12 to 18 inches is typical.
3. Find the pitch from the attic or with our roof pitch calculator.

Measuring on the roof

For a cut-up roof, the "Roof planes" tab is more accurate. Measure each face along the eave and then straight up the slope to the ridge. Hip roof ends are triangles. The long sides of a hip roof are trapezoids, wide at the eave and narrow at the ridge. If you only want square footage and no materials list, our roof square footage calculator handles roofs with several different pitches.

How many bundles of shingles do I need? Formula and worked example

Roof area = (length + 2 × overhang) × (width + 2 × overhang) × pitch multiplier
Bundles = roof area × (1 + waste) ÷ coverage per bundle, rounded up
Starter bundles = (eaves + rakes) ÷ 110 ft
Cap bundles = (ridges + hips) ÷ 25 ft
Underlayment rolls = roof area × 1.1 ÷ roll coverage
Nails = squares to order × 320 (or 480 for high wind)

Worked example. A 50 by 28 ft house with a 12-inch overhang and a 6/12 gable roof.

• Footprint with overhangs: 52 × 30 = 1,560 sq ft.
• Roof area: 1,560 × 1.118 = 1,744 sq ft, or 17.44 squares.
• With 10% waste: 1,744 × 1.10 = 1,919 sq ft, or 19.2 squares.
• Shingles: 1,919 ÷ 33.3 = 57.6, so 58 bundles.
• Edges: eaves are 2 × 52 = 104 ft. Each rake is (14 + 1) × 1.118 = 16.8 ft, and there are four, so 67.1 ft. The ridge is 52 ft.
• Starter: 104 + 67.1 = 171.1 ft ÷ 110 = 2 bundles. Hip and ridge cap: 52 ÷ 25 = 3 bundles.
• Synthetic underlayment: 1,744 × 1.1 ÷ 1,000 = 1.9, so 2 rolls. One row of ice and water shield: 104 × 3 ft × 1.1 ÷ 200 = 2 rolls.
• Drip edge: 171.1 ft ÷ 10 = 18 pieces. Nails: 19.19 squares × 320 = about 6,140 nails, roughly 48 lb, so one 7,200-count box.

Those are the default numbers in the calculator above, so you can check them against the shopping list.

Shingle accessories: what each one covers

These are common US package sizes. Brands differ, so the calculator lets you change the coverage figures.

A few rules of thumb sit behind those numbers. We add 10% to underlayment and ice and water shield for side and end laps. Drip edge goes on the eaves under the underlayment and on the rakes over it. Starter strip on the rakes is optional, but most manufacturers recommend it because it seals the edge against wind. Three-tab shingles cut into thirds can stand in for cap shingles, but architectural roofs need real cap bundles.

3-tab vs architectural vs premium shingles

• 3-tab: flat, single-layer shingles with a uniform look. The cheapest option, typically $30 to $40 a bundle. They're lighter and less wind-resistant, and many suppliers stock fewer of them now.
• Architectural (dimensional): two laminated layers that give a shadow line. This is the standard on most US reroofs today, at roughly $35 to $50 a bundle. Most are still three bundles per square.
• Premium (designer): heavy shingles made to look like slate or wood shake, at about $55 to $90 a bundle. Some come four or five bundles to a square. If yours do, set coverage to 25 or 20 sq ft.

Nailing matters as much as the shingle. The standard pattern is four nails per shingle. In high-wind areas, or when the manufacturer requires it for a wind warranty, use six. That raises nails from about 320 to 480 per square. Set the nailing pattern above and the nail count, weight and boxes update.

Pitch limits apply to every type. Asphalt shingles aren't allowed below 2/12. From 2/12 up to 4/12, the code calls for two layers of underlayment (IRC R905.2.2), and the calculator doubles your underlayment rolls in that range. Use our roof slope calculator to check other materials.

What a shingle roof costs

Materials are usually a third or less of the job. The calculator shows both numbers. The installed range uses the same figure as our other roofing tools: $4 to $10 per sq ft of roof for asphalt shingles, as typical US installed prices. That's $400 to $1,000 per square. What moves you within that range:

• Steepness. At 8/12 and 9/12 crews need roof jacks and harnesses, so we add about 10%. At 10/12 to 12/12 we add 20%, and above 12/12 we add 30%.
• Tear-off. Removing old shingles and hauling them away is extra. We use about $1 to $2 per sq ft for each layer. Two layers cost more to remove and often hide damaged decking.
• Decking. Soft or rotted sheathing is replaced per sheet once the old roof is off. Ask for a per-sheet price in writing.
• Complexity. Valleys, dormers, skylights and chimneys mean more cutting, more flashing and more labor.
• Shingle grade. Premium shingles cost more and take longer to install.

For a fuller quote, including permits, decking and region, use the roof replacement cost estimator. If you only need to fix part of a roof, see roof repair cost per square foot or our guide to missing shingles and leaks.

Tips before you order shingles

• Order from one production run. Colors vary a little between runs. Buy every bundle at once and check the lot numbers match.
• Keep two or three bundles extra. Unopened bundles can often be returned. A bundle from the same lot is very handy for storm repairs later.
• Don't trust the house's living area. Square footage from a listing includes every floor and leaves out the garage and overhangs. Measure the footprint.
• Plan the vents. If you add ridge vent, you need enough soffit intake to balance it. Our roof vent calculator sizes both.
• Ice and water shield. Where ice dams are common, building codes require it to run from the eave to at least 24 inches inside the exterior wall. With a 12 to 18-inch overhang that usually takes two rows. It also belongs in valleys and around chimneys and skylights.
• Frame first, then shingle. Building a new roof or a shed? Our rafter length calculator gives cut lengths and the birdsmouth layout.

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