# Roofing Calculator

Roofing Calculator is an online tool to calculate roofing material estimate for installation area, estimate the cost of installation, calculate number of squares required, estimate how many bundles of 3-tab asphalt shingles and number of rolls of 15lb felt are needed for new roof. Add the price per square of materials to get an estimated material cost.

## Roofing Material Estimate Formulas

### The Size of the Roof in Squares

To find the squares, divide the overall roof area by 100 and then round up.

### Overall Installation Roofing Area

Roofing Area=Length x Width x Roof Pitch

Roof pitch is the measurement of a roof's vertical rise divided by its horizontal run. It is often compared to slope, but is not exactly the same. Roof pitch is a determining factor for cost of the roof, as well as the roof area, and the type of materials used.

### How Many Bundles of Shingles Will You Need

The average bundle of shingles covers 33.3 ft2, so three bundles of shingles are needed per square.

Total bundles of 3-tab asphalt shingles required: Total Installation Area / 33.3

### Number of Rolls of 15lb felt

Roofing felt is sold by the roll. The average roll of 15-pound roofing felt covers about 400 ft2, or 4 squares

Number of Rolls=Area / 400

### Estimated Material Cost

Total Cost=Number of Squares x Price per Square

#### Roof Pitch - Typical Slope Correction Factors

Pitch Angle Multiply By Pitch Angle Multiply By
0/12 1
1/12 4.8° 1.003 2/12 9.5° 1.014
3/12 14° 1.031 4/12 18.4° 1.054
5/12 22.6° 1.083 6/12 26.6° 1.118
7/12 22.6° 1.158 8/12 26.6° 1.202
9/12 36.9° 1.250 10/12 33.7° 1.302
11/12 42.5° 1.357 12/12 45.6° 1.414
13/12 47.3° 1.474 14/12 49.4° 1.537
15/12 51.3° 1.601 16/12 53.1° 1.667
17/12 54.8° 1.734 18/12 56.3° 1.803
19/12 57.7° 1.873 20/12 59.0° 1.944
21/12 60.3° 2.016 22/12 61.4° 2.088
23/12 62.4° 2.162 24/12 63.4° 2.236

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