Roofing Calculator - Estimate Shingles, Squares & Materials

How to Use the Roofing Calculator

1. Enter roof dimensions — input the length and width of each roof plane (if you have multiple sections, calculate each separately)
2. Set roof pitch — enter the rise in inches per 12 inches of run (e.g., 6 for a 6/12 pitch). Common residential pitches range from 4/12 to 9/12
3. Adjust waste allowance — the default 10% accounts for cutting waste, hips, valleys, and starter strips
4. Get materials — instantly see roof squares, shingle bundles, underlayment rolls, ridge cap linear feet, and approximate weight

Perfect for roofing contractors, homeowners planning a replacement, and material estimators. All calculations run in your browser — nothing is uploaded.

Features

• Roof pitch adjustment — the slope factor automatically adjusts the effective roof area
• Squares calculation — uses the industry standard where 1 square = 100 square feet of roof surface
• Bundle count — estimates based on 3 bundles per square (standard 3-tab shingles)
• Underlayment — calculates #15 felt roll count (1 roll covers approximately 4 squares)
• Ridge cap — estimates linear feet of cap shingles needed for ridges and hips
• Waste allowance — automatically adds 10% but you can adjust it for your specific roof complexity

Use Cases

• Home roof replacement — get accurate material quantities before contacting contractors for quotes
• New construction — budget roofing materials during the planning phase of a building project
• Contractor bidding — prepare quick material estimates for roofing job proposals
• DIY roof repair — calculate exactly what you need for small sections or garage roofs
• Insurance estimates — provide material quantities to insurance adjusters for damage claims

FAQ

How many shingle bundles do I need per square?

Standard 3-tab asphalt shingles come 3 bundles per square. Architectural or dimensional shingles may also be 3 bundles per square, but check the manufacturer’s specifications as coverage can vary.

How do I measure roof pitch if I don’t know it?

Use a level and measuring tape. Place the level horizontally against the roof, measure 12 inches along it, then measure the vertical distance from the level to the roof surface at that point — that’s your pitch.

Should I order extra materials?

Always order 10-15% extra for waste. Complex roofs with many valleys, hips, and penetrations require more waste allowance than simple gable roofs.

Does the calculator work for metal roofing?

The square footage and pitch calculations are the same, but metal roofing panels are sold by the sheet rather than by the bundle. Use the squares output and check with your supplier for panel coverage.

Tips

• Measure from the roof surface, not from the ground — ground measurements miss the slope factor
• Add 15% waste instead of 10% for roofs with multiple valleys, dormers, or complex shapes
• Order all materials at once to ensure color matching across batches
• Don’t forget accessories: ridge vent, drip edge, flashing, and pipe boots aren’t included in basic material estimates