Roofing Calculator
Enter your roof size and local prices — empty prices count as zero
Roofing Calculator: Estimate Shingles and Total Roof Cost
A roofing calculator turns the size and slope of your roof into a shopping list and a budget. Enter the floor-plan area (or length and width), choose the pitch, set a waste allowance and add your local prices. This free roofing calculator then shows the roof surface, the number of roofing squares, how many shingle bundles, underlayment rolls, ridge cap bundles and pounds of nails you need, plus tear-off, labor and a total estimate. It works in feet or meters.
Quick answer: a 1,500 sq ft plan area with a 5/12 pitch and 10 percent waste has about 1,788 sq ft to cover, which is 17.88 squares. That needs 54 bundles of architectural shingles, and the estimate comes to about $5,545 with the default prices.
How Roof Area Is Calculated
A sloped roof is larger than the floor space beneath it. The pitch factor corrects for that, and waste is added on top.
The table shows how pitch changes the surface for the same 1,500 sq ft plan area.
| Roof pitch | Pitch factor | Roof surface for a 1,500 sq ft plan |
|---|---|---|
| 2/12 | 1.014 | 1,521 sq ft |
| 4/12 | 1.054 | 1,581 sq ft |
| 5/12 | 1.083 | 1,625 sq ft |
| 6/12 | 1.118 | 1,677 sq ft |
| 8/12 | 1.202 | 1,803 sq ft |
| 10/12 | 1.302 | 1,953 sq ft |
| 12/12 | 1.414 | 2,121 sq ft |
Worked Example
Take a 1,500 sq ft plan area, a 5/12 pitch, 10 percent waste and the default prices. The roof surface is 1,625 sq ft, or 16.25 squares, and 1,788 sq ft after waste.
| Item | Quantity | Cost |
|---|---|---|
| Architectural shingles | 54 bundles | $2,052 |
| Underlayment and nails | 2 rolls, 18 lb | $214 |
| Ridge and hip caps | 2 bundles | $110 |
| Tear-off, 1 layer | 16.25 squares | $731 |
| Labor | 16.25 squares | $2,438 |
| Total | $5,545 |
Shingle Types and Coverage
The shingle you choose affects the price per bundle, how long the roof lasts and how many bundles each square needs. Picking a type in the calculator sets a typical bundle price, which you can overwrite with a quote from your supplier.
| Shingle type | Bundles per square | Typical lifespan |
|---|---|---|
| 3-tab asphalt | 3 | 15 to 20 years |
| Architectural asphalt | 3 | 25 to 30 years |
| Premium or designer | 4 | 30 years or more |
What Else Goes on a Roof?
Underlayment sits between the deck and the shingles, and one roll normally covers about 1,000 sq ft. Ridge and hip caps finish the peaks, with a bundle covering roughly 33 linear feet. Nails are estimated at about one pound per square. Items that depend on the job, such as flashing, vents, drip edge, decking repairs, chimneys and skylights, are not included, so add them to your budget separately.
Tips to Keep Roofing Costs Down
Get at least three written quotes and compare them by the square. Order materials with a small spare allowance, and schedule work for dry weather to avoid delays. If an old roof has more than one layer, tear-off is often required, so ask about it early. For planning the surrounding work, the concrete calculator, paint calculator and area calculator can help with other parts of a build or repair.
Limits of This Calculator
The estimate works for simple and moderately complex pitched roofs covered with asphalt shingles. Metal, tile and slate roofs, flat membrane roofs and very complex shapes use different materials and methods. Treat the result as a planning figure and let a roofer measure the roof before you commit.
Who Can Use This Calculator?
Homeowners planning a re-roof, landlords and property managers, roofing contractors preparing quotes, builders ordering materials, and anyone comparing roofing bids.
How to Use This Roofing Calculator
Enter the roof size
Type the floor-plan area, or switch to length and width. Choose feet or meters.
Set the pitch and waste
Pick the roof pitch, then adjust the waste slider for the complexity of the roof.
Add your prices
Choose a shingle type and enter prices for bundles, underlayment, ridge caps, tear-off and labor. Leave a price empty to count it as zero.
Read the estimate
See the roof area, squares, material quantities and the total cost update as you type.