What is a 'square' in roofing?

A 'square' is a roofing unit of measure equal to 100 square feet. For example, a 2,000 sq ft roof is 20 squares.

How many bundles of shingles do I need?

Standard 3-tab or architectural shingles typically cover 33.3 sq ft per bundle. Therefore, you need 3 bundles to cover one square (100 sq ft).

How does roof pitch affect cost?

Pitch increases the surface area. A steep roof (e.g., 12/12 pitch) has 40% more surface area than a flat roof with the same footprint. Steep roofs also cost more in labor due to safety requirements.

Can I layer new shingles over old ones?

While allowed in some areas (up to 2 layers), it's generally not recommended. It shortens the lifespan of new shingles, hides deck damage, and adds significant weight to the structure.

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Roof Calculator

Calculate roofing materials and costs for your project.

Calculator

Roof Length (feet)

Roof Width (feet)

Roof Pitch (rise/run)

Price per Square ($) 1 square = 100 sq ft

Results

Estimated Materials

0.00 Squares

Approx. 0 Bundles

Roof Area (with pitch): 0.0 sq ft

Shingle Cost: $0.00

Underlayment (Est): $0.00

Total Material: $0.00

Reviewed by Mark Johnson, Licensed Contractor | Last Updated: November 2025

Planning Your Roofing Project

Estimating roofing materials involves more than just length times width. The pitch (slope) of your roof significantly increases the surface area, and waste factors must be accounted for to avoid running short.

💡 Expert Tip: Don't Forget Accessories

"The biggest mistake DIYers make is only calculating the field shingles. You also need starter strips for the eaves, ridge caps for the peaks, and drip edge flashing. These can add 10-15% to your total material cost."

Common Mistakes to Avoid

Ignoring Pitch: A 12/12 pitch roof needs 42% more shingles than a flat roof covering the same house footprint. Always use the pitch multiplier.
Underestimating Waste: For simple gable roofs, 10% waste is fine. For hip roofs or roofs with many valleys and dormers, budget 15-20% for cutting waste.
Skipping Ventilation: A new roof needs proper intake (soffit) and exhaust (ridge) ventilation to prevent heat buildup and ice dams.

Frequently Asked Questions

What is the average cost of a new roof?

The national average is between $8,000 and $16,000. Asphalt shingles are the most affordable ($3.50-$5.50 per sq ft installed), while metal or slate can cost 3-5 times more.

How do I know my roof pitch?

Pitch is the rise in inches for every 12 inches of run. You can measure it from the attic with a level and tape measure, or use a smartphone app. Common pitches are 4/12 (low), 6/12 (medium), and 8/12+ (steep).

What is architectural vs. 3-tab shingle?

3-tab shingles are flat and uniform. Architectural (dimensional) shingles are thicker, have a layered look, last longer (30-50 years vs 20 years), and are more wind-resistant.