Roof Shingle Calculator (Squares and Bundles)
Find how many squares and bundles of shingles a roof needs. Enter the building size, overhang and pitch to get roof area, bundles, underlayment rolls, nails and cost.
Added to every side of the footprint.
Enter 0 for a flat roof.
One square covers 100 ft².
Enter the building length and width, and the roof pitch.
About the roof shingle calculator
The Roof Shingle Calculator answers one question: how many bundles of shingles do I need? Enter the length and width of the building, the roof pitch and the overhang. The calculator finds the sloped roof area, adds a waste allowance, converts the result to roofing squares and rounds up to whole bundles. It also reports the underlayment rolls and nails that go with the same area, and a cost if you add a price per square.
Shingles are sold in bundles, but roofs are measured in square feet or square metres, and the gap between the two is where orders go wrong. Ordering too few bundles can leave you waiting on a second delivery, and the new bundles may come from a different production batch with a slightly different color. The goal here is a count you can take to the supplier.
How bundles are worked out
From footprint to bundles
- Add the overhang to both sides of each dimension, then multiply to get the effective footprint.
- Multiply by the slope factor to get the true roof area.
- Add the waste allowance: 10 percent for a simple roof, 15 percent for a complex one.
- Divide by 100 square feet to get squares.
- Multiply by 3 and round up to a whole bundle.
Formula
With a pitch of inches of rise per 12 inches of run, a length , a width , an overhang and a waste allowance :
If you know the pitch as an angle instead, the slope factor is , which gives the same answer.
Three bundles to the square
A roofing square is 100 square feet, and most asphalt shingles are packaged so that three bundles cover one square. That is the rule the calculator uses. Some thicker laminated or designer shingles are packed four or five bundles to the square, so read the coverage on the wrapper. If yours differ, multiply the squares shown by the bundles per square on your product instead of using the bundle figure directly.
Waste rules
Waste covers the shingles you cut at edges, hips, valleys and the ridge, plus damaged pieces and a few spares. A plain gable roof wastes the least, so the calculator adds 10 percent. A roof with valleys, dormers, chimneys or many small sections needs more cutting, so the complex setting adds 15 percent. Waste is applied before rounding, so you always end up with whole bundles and some margin.
Worked examples
Rounding up. A 36 ft by 24 ft building at 30 degrees with a 1.5 ft overhang has a roof area of 1,215.9 square feet. With 10 percent waste that is 13.37 squares. Multiplied by 3 it gives 40.12 bundles, and rounding up gives 41. Even a tiny excess adds a whole bundle.
Effect of waste. A 40 ft by 30 ft building at 6:12 with a 1 ft overhang has a roof area of 1,502.6 square feet. As a simple roof it needs 16.53 squares, so 50 bundles. As a complex roof it needs 17.28 squares, so 52 bundles. Without any overhang, the simple roof falls to 14.76 squares and 45 bundles. That shows how much the overhang matters.
Metric. A 10 m by 8 m building with a 0.3 m overhang and a 6:12 pitch has a roof area of 101.9 square metres, which is 1,097.1 square feet. With 10 percent waste that is 12.07 squares, or 37 bundles.
Pitch and shingle choice
Standard asphalt shingles are designed for pitches of 4:12 and above. Many manufacturers allow them down to 2:12 only with special underlayment, and below that a different roof covering is needed. A very steep roof, over about 8:12, can require extra fasteners or staging, and the slope factor makes the area noticeably larger. Always check the manufacturer's installation instructions and your local building rules.
What is not included
Ridge cap shingles, starter strips, drip edge, flashing and vents are separate items. The bundle count covers the field of the roof only, so add these based on the length of your ridge, hips and eaves.
Comparing prices
Quotes may come per bundle or per square. Since three bundles make a square, divide a per-square price by three to compare it with a per-bundle price. The Unit Price Calculator helps compare packs of different sizes. To convert the area into other units, use the Area Converter.
Privacy
Nothing is uploaded; every calculation runs in your browser and never leaves your device.
Related tools
The full Roofing Calculator covers area, squares, underlayment and cost on one page. For a wider job, the Floor Tile Calculator and Paint Calculator estimate other finishing materials.
Frequently asked questions
How many bundles of shingles are in a square?
Most asphalt shingles come three bundles to the square, and one square covers 100 square feet of roof. The calculator uses 3. Thicker laminated or specialty shingles can be four or five bundles to the square, so check the label and scale the number of squares accordingly.
Why does the bundle count always round up?
You cannot buy part of a bundle. The calculator multiplies the squares including waste by 3 and rounds up, so 40.12 becomes 41. That guarantees enough shingles for the area you entered.
How much extra should I order for waste?
The calculator adds 10 percent for a simple gable or hip roof and 15 percent for a complex roof with valleys, dormers or chimneys. Cutting at edges, hips, valleys and the ridge accounts for most of the waste.
Does the bundle count include ridge cap and starter strips?
No. It covers the main roof surface only. Ridge cap shingles, starter strips, drip edge and flashing are separate products, so add them using the length of your ridge, hips and eaves.
Can I use shingles on a low-slope roof?
Standard asphalt shingles are meant for pitches of 4:12 and above. Some manufacturers allow 2:12 to 4:12 with special underlayment, and flatter roofs need a different covering. The calculator accepts any pitch, so check your product's installation instructions.
Why do I get a different bundle count from another calculator?
Small differences usually come from the overhang, the waste percentage or how pitch is handled. This calculator applies the pitch to the whole footprint plus overhang, adds 10 or 15 percent waste, then rounds up. Compare those three inputs first.
Is my data sent anywhere?
No. The shingle and bundle sums run in your browser, so your building dimensions, pitch and prices are never uploaded or stored on a server. They stay on this device and are not shared with anyone.