Roofing Shingle Calculator
Estimate roof area, roofing squares and shingle bundles from a house's footprint and roof pitch.
Calculator
| Roofing squares (+10%) | 14.8 squares |
|---|---|
| Roof surface area | 1,342 ft² |
| Pitch multiplier | 1.118 × |
How it is calculated
Roof area ≈ footprint × pitch multiplier = 30 × 40 × 1.118 = 1,342 sq ft = 13.4 squares. Add 10% for waste and starter/ridge: 14.8 squares × 3 bundles = 45 bundles.
About this calculator
A roofing square is 100 square feet of roof surface. Shingles are packaged in bundles, and standard asphalt shingles are commonly sold at about three bundles per square. Some thicker products use four or more, so check the package.
This calculator estimates roof surface from the house footprint and pitch: a steeper roof has more surface than the footprint, so the footprint is multiplied by a pitch factor. It then adds 10% for waste and for starter and ridge pieces. Roofs with hips, valleys and dormers waste more, and a roofer's on-site measurement is more precise.
Worked examples
| Project | Bundles of shingles (+10%) | Rough cost |
|---|---|---|
| a 30x40 ft house footprint with a 6/12 roof pitch | 45 bundles | $5,165 – $9,593 |
| a 24x36 ft house footprint with a 4/12 roof pitch | 31 bundles | $3,506 – $6,512 |
| a 30x50 ft house footprint with a 8/12 roof pitch | 60 bundles | $6,941 – $12,890 |
| a 40x60 ft house footprint with a 6/12 roof pitch | 89 bundles | $10,331 – $19,185 |
Buying notes
- Confirm the bundles per square on the package you plan to buy.
- Underlayment, flashing, drip edge, ridge caps and nails are separate items.
- A waste allowance of 10 to 15 percent is typical; use more for complicated roofs.
Further reading
Quick answers by size
Click a size for the exact quantity and cost.
How to measure and use this calculator
- Measure the house footprint length and width, including garage and any overhang that is under the roof.
- Find the pitch, which is the rise per 12 inches of run (for example 6/12).
- Enter the numbers. The calculator turns footprint into roof surface and then into squares and bundles.
- Add allowances for hips, valleys, starter and ridge pieces.
Common mistakes
- Using only the footprint and ignoring pitch.
- Forgetting overhangs and dormers.
- Not budgeting for underlayment, flashing and tear-off.
Tips
- One roofing square is 100 sq ft, and most shingles come 3 bundles to the square.
- Steeper pitches add surface area; the multiplier accounts for that.
- Hips, valleys and dormers raise waste; ask a roofer to measure complex roofs.
Frequently asked questions
How many bundles of shingles per square?
Three bundles cover one roofing square (100 sq ft) for most architectural and 3-tab shingles.
What does a 6/12 roof pitch mean?
The roof rises 6 inches for every 12 inches of horizontal run.
How many squares is a 2,000 square foot roof?
2,000 ÷ 100 = 20 squares, before adding waste.