Roofing Material Estimator

Estimate roofing materials including shingles, underlayment, and ridge caps based on roof dimensions and pitch.

Roof Footprint (Including Overhangs)

Length (feet along eaves)

Width (feet from eave to eave)

Roof Pitch (Rise / 12-inch Run)

Waste Allowance (%)10% for simple gable; 15%–20% for hip roofs with valleys.

Roofing Material Estimates

SPEC_VERIFIED

Roofing Squares (100 sq ft each)

14.76squares

Shingle Bundles (3 per square)

45bundles

Detailed Material Breakdown

Actual Pitched Roof Area (with waste): 1475.76 sq ft
Flat Footprint Area: 1200 sq ft
Pitch Multiplier: 1.1180
Underlayment Rolls (400 sq ft/roll): 4rolls
Ridge Cap Shingles Needed: 40 linear feet

ℹThis roofing estimator provides approximate material quantities for planning purposes only. It does not replace on-site physical inspection, wind-load assessments, structural engineering, or local building code requirements. Always consult a licensed roofing professional before ordering.

This estimator provides approximate material quantities for planning purposes only. It does not replace on-site structural inspections, wind-load assessments, or local building code compliance. Always consult a licensed roofing contractor before ordering.

Calculation Formula & Assumptions

Calculates true roof surface area from flat footprint dimensions and roof pitch, and estimates roofing squares, shingle bundles, and underlayment rolls.

Squares = (Flat Area × √(1 + (Pitch/12)²) × (1 + Waste %)) ÷ 100

Step-by-step breakdown:

Calculate flat footprint area: Area = Length × Width
Compute pitch multiplier: Multiplier = √(1 + (Pitch ÷ 12)²)
True Roof Area = Flat Area × Pitch Multiplier
Add waste factor (10% for simple gable; 15%–20% for hip roofs or dormers)
Roofing Squares = Area with Waste ÷ 100 sq ft
Shingle Bundles = Roofing Squares × 3 (standard shingles are 3 bundles per square)
Underlayment Rolls = ⌈Area with Waste ÷ 400 sq ft⌉

Note: 1 roofing square = 100 square feet of surface area. 3 bundles of standard architectural shingles cover 1 square.

Worked Calculation Example

Ranch House Roof (40×30 ft, 6/12 Pitch)

Re-roofing a gable roof with flat dimensions of 40×30 ft including eaves, with a 6/12 pitch and 10% waste.

Dimensions:40 ft × 30 ft = 1,200 sq ft flat area

Pitch:6/12 (6 inches rise per 12 inches run)

Waste Factor:10%

Calculation Steps:

Flat footprint = 40 × 30 = 1,200 sq ft
Pitch multiplier = √(1 + (6/12)²) = √(1.25) = 1.1180
True roof area = 1,200 × 1.1180 = 1,341.60 sq ft
With 10% waste: 1,341.60 × 1.10 = 1,475.76 sq ft
Roofing squares = 1,475.76 ÷ 100 = 14.76 squares
Shingle bundles = 14.76 × 3 = 44.28 => 45 bundles
Underlayment rolls = 1,475.76 ÷ 400 = 3.69 => 4 rolls

Order 15 squares (45 bundles) of asphalt shingles and 4 rolls of underlayment.

How to Use This Calculator

Enter roof length and width (including eave overhangs).
Select roof pitch (e.g., 4/12 for moderate slope; 8/12 or 12/12 for steep roofs).
Set waste allowance (10% gable, 15% hip roof with valleys).