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.
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.
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.