Roofing & Shingle Calculator
Estimate sloped roof area, roofing squares, shingle bundles, underlayment rolls, drip edge, ridge length and material cost.
Default project preview
15.63 squares
Shingle bundles
47
Underlayment
4 rolls
Roof surface
1,421 ft²
Drip edge
144 ft
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Building length
Enter this project assumption in ft. The current imperial default is 40 ft.
Building width
Enter this project assumption in ft. The current imperial default is 30 ft.
Eave overhang
Enter this project assumption in ft. The current imperial default is 0.5 ft. Minimum: 0.
Roof pitch rise
Enter this project assumption in per 12. The current imperial default is 6 per 12. Minimum: 0.
Waste allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Coverage per bundle
Enter this project assumption in ft². The current imperial default is 33.3 ft².
Underlayment roll coverage
Enter this project assumption in ft². The current imperial default is 400 ft².
Price per shingle bundle
Enter this project assumption in a unitless value. The current imperial default is 36. Minimum: 0.
Price per underlayment roll
Enter this project assumption in a unitless value. The current imperial default is 75. Minimum: 0.
How to read the outputs
Shingle bundles
33.3 ft² each. Default preview: 47.
Underlayment
rounded to full rolls. Default preview: 4 rolls.
Roof surface
before waste. Default preview: 1,421 ft².
Drip edge
roof perimeter estimate. Default preview: 144 ft.
Ridge length
simple gable roof. Default preview: 41 ft.
Material cost
shingles and underlayment. Default preview: $1,992.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Roof area = plan dimensions including overhang × √(12² + pitch rise²) ÷ 12. Order area = roof area × waste factor. Bundles and rolls are always rounded up.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Roofing & Shingle Calculator questions
How many bundles make one roofing square?+
Many standard asphalt shingles use about three bundles per 100 square feet, but bundle coverage varies. Use the coverage printed on the exact product.
Does roof pitch change material quantity?+
Yes. A steeper roof has more surface area than its horizontal footprint, so the calculator applies a slope factor.
Should I add more waste for hips and valleys?+
Usually yes. Complex roofs and patterned shingles often require a larger allowance than a simple gable roof.
Project guide
Use this calculator with confidence
Last reviewed: July 19, 2026
The roofing calculator estimates sloped roof area, roofing squares, bundles and cost from plan dimensions and pitch. It applies a pitch multiplier, then adds waste before rounding packages upward. Valleys, hips, dormers, starter strips, ridge caps, flashing and local wind or fire requirements are separate details; use this page to establish the main field-shingle quantity, not to design the roof system.
How to use it
- 1Measure horizontal roof plan dimensions, not the sloped rafter length.
- 2Enter the correct rise-over-run pitch for each roof section.
- 3Calculate separate sections when pitches differ.
- 4Choose waste based on valleys, hips, cuts and package requirements.
Worked example
A 30 ft × 40 ft simple roof plan is 1,200 ft². At 6:12 pitch the multiplier is about 1.118, producing about 1,342 ft² of slope area. With 10% waste, plan roughly 14.8 roofing squares before package rounding.
What the defaults mean
Pitch multiplier
Converts horizontal plan area into sloped surface area.
10% waste
A simple-roof starting point; complex roofs often need more.
Bundles per square
Product-specific and must match the selected shingle.
| Pitch | Approx. multiplier | Slope area for 100 ft² plan |
|---|---|---|
| 4:12 | 1.054 | 105.4 ft² |
| 6:12 | 1.118 | 111.8 ft² |
| 8:12 | 1.202 | 120.2 ft² |
| 12:12 | 1.414 | 141.4 ft² |
Common measurement mistakes
- Measuring sloped length and also applying a pitch multiplier.
- Combining roof sections with different pitches.
- Ignoring starter, ridge, valley and flashing products.
- Assuming every shingle line has the same bundles per square.
Limits and safety
- Roof access and fall protection require qualified planning.
- Does not determine deck condition, ventilation or code compliance.
- Confirm package coverage and accessory requirements with manufacturer documents.
Continue the project
calculate roof pitch and multiplier — Confirm the geometric slope factor.
estimate roofing underlayment — Plan rolls and overlaps separately.
estimate roofing nail quantity — Use the project area and fastening rate.
calculate ridge-cap pieces — Measure ridge and hip lengths after field shingles.
estimate roof flashing — Plan valleys, walls, eaves and penetrations.