Roofing & Shingles Calculator
Calculate how many shingles, bundles, underlayment rolls, and ridge caps you need for your roofing project.
How to Calculate Roofing Materials
Roofing is measured in "squares" — one square equals 100 square feet. To find your roof area, multiply the length by the width (rafter length from ridge to eave) and multiply by the number of sides. Then apply a pitch multiplier to account for the slope, and add a waste factor for cuts, valleys, and starter strips.
Roofing Material Coverage
| Material | Coverage | Notes |
|---|---|---|
| 3-Tab Shingles | 3 bundles per square | Most affordable, 20–25 year warranty |
| Architectural Shingles | 3–4 bundles per square | Thicker, 30–50 year warranty |
| 15 lb Felt Underlayment | ~400 sq ft per roll | 4 sq ft overlap per course |
| Synthetic Underlayment | ~1,000 sq ft per roll | Lighter, more durable than felt |
| Ridge Cap Shingles | ~33 linear ft per bundle | For ridges and hips |
Understanding Roof Pitch
Roof pitch is expressed as the number of inches the roof rises vertically for every 12 inches of horizontal run. For example, a 4/12 pitch means the roof rises 4 inches for every 12 inches horizontally. Steeper roofs require more material because the actual surface area is larger than the footprint. A 4/12 pitch adds about 6% more area, while a 12/12 (45-degree) pitch adds 41%.
When to DIY vs. Hire a Pro
Roofing can be a DIY project for single-story homes with low-pitch roofs (4/12 or less). However, for steep roofs, multi-story homes, or if your area requires permits and inspections, hiring a licensed roofer is strongly recommended. A professional crew can complete most residential roofs in 1–2 days, and their work typically comes with a warranty.
Tips for Your Roofing Project
- Check local building codes — most areas allow a maximum of two shingle layers before a full tear-off is required.
- Install ice and water shield in valleys and along eaves in cold climates to prevent ice dam damage.
- Replace damaged or rotted decking (plywood/OSB) before installing new shingles.
- Always install drip edge along eaves and rakes to direct water away from the fascia.
- Start shingling from the bottom (eave) and work upward, overlapping each course per manufacturer specs.
- Choose a cool, dry day with temperatures between 40–85°F for best shingle adhesion.
Frequently Asked Questions
Shingles are sold in bundles, and it takes 3 bundles to cover one roofing square (100 sq ft). To find your bundle count, calculate your total roof area in square feet (including pitch multiplier and waste), divide by 100 to get squares, then multiply by 3. A 2,000 sq ft roof with 10% waste needs about 66 bundles.
A roofing square is a standard unit of measurement equal to 100 square feet of roof area. Roofers and suppliers use squares to simplify ordering and pricing. For example, a 2,000 sq ft roof is 20 squares. Shingles are priced per bundle, and most asphalt shingles require 3 bundles per square.
Standard 3-tab asphalt shingles last 15-25 years, while architectural (dimensional) shingles last 25-50 years depending on quality and climate conditions. Factors affecting lifespan include ventilation, sun exposure, climate extremes, and installation quality. Premium architectural shingles with enhanced warranties can last 40-50 years in favorable conditions.
Most building codes allow one layer of new shingles over existing shingles, but never more than two total layers. Reroofing over existing shingles is cheaper and faster, but a full tear-off is recommended for better results and longer lifespan. You must tear off if shingles are curling, if there is deck damage, or if you already have two layers.
For a typical 2,000 sq ft roof, DIY material costs range from $1,500-$4,000 depending on shingle quality. Professional roof replacement costs $5,000-$12,000 for asphalt shingles, including tear-off, materials, and labor. Prices vary significantly by region, roof complexity, and the number of layers being removed.