Roofing Calculator
Pitch Multipliers
Shingle Types
Related Calculators
Roofing Guide
Understanding Roofing Measurements
Roofing materials are measured in "squares." One roofing square equals 100 square feet of roof area. To calculate squares, measure the footprint and multiply by the pitch factor.
Calculating Roof Area
Roof Pitch Explained
Roof pitch is expressed as rise/run, where the first number is vertical inches of rise per 12 inches of horizontal run. A 6/12 pitch rises 6 inches for every 12 inches of run.
| Pitch | Angle | Multiplier | Type |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Low slope |
| 4/12 | 18.4° | 1.054 | Moderate |
| 6/12 | 26.6° | 1.118 | Standard (most common) |
| 8/12 | 33.7° | 1.202 | Steep |
| 10/12 | 39.8° | 1.302 | Very steep |
| 12/12 | 45° | 1.414 | Steep/architectural |
Materials Needed
Per Square (100 sq ft)
- 3 bundles of shingles
- ~320 roofing nails
- 2-3 lbs of nails
Additional Materials
- Underlayment (ice/water shield)
- Drip edge
- Ridge cap shingles
- Starter strip
- Roof vents
Waste Factors
- 10%: Simple gable roof with few obstacles
- 15%: Standard roof with some dormers or valleys
- 20%: Complex roof with multiple hips, valleys, dormers
- 25%+: Very complex design or steep pitch
Frequently Asked Questions
What is a roofing square?
A roofing square equals 100 square feet of roof area. It's the standard unit for ordering roofing materials. Three bundles of standard shingles typically cover one square.
How do I calculate roof area from the ground?
Measure the footprint (length x width), then multiply by the pitch factor. A 6/12 pitch has a 1.118 multiplier. For a 30x40 ft footprint with 6/12 pitch: 1200 x 1.118 = 1,342 sq ft = 13.4 squares.
How much waste should I factor for roofing?
Add 10% waste for simple gable roofs, 15% for roofs with some dormers or valleys, 20% for complex designs with multiple angles, and 25%+ for very complex roofs or steep pitches.
How many bundles of shingles do I need?
Standard asphalt shingles require 3 bundles per square. For 15 squares of roof, you'd need 45 bundles. Always round up and add waste factor. Architectural shingles may vary - check manufacturer specs.