How many shingles do I need per square?

For 3-tab shingles, 3 bundles cover one roofing square (100 sq ft). Architectural shingles may need 4 bundles per square.

What is a roofing square?

One roofing square equals 100 square feet of roof area. A typical residential home requires 20-30 squares.

How much extra shingles should I buy?

Add 10% extra for simple roofs and up to 20% for complex roofs with many valleys, hips, and dormers.

WHOLE

CALCULATOR

Roofing Calculator

House Dimensions

House Length (ft)

House Width (ft)

Eaves Overhang (ft)

Footprint with eaves: 0 sq ft

Roof Configuration

Roof Type

Roof Pitch

Pitch: 6/12 • Angle: 26.6° • Correction factor: 1.118

Roofing Material

Price (per sq ft)

Include 10% waste allowance

Roofing Material Estimate

Footprint Area

0 sq ft

Actual Roof Area

0 sq ft

Roofing Squares

Shingle Bundles

Ridge Length

0 ft

Rake Length

0 ft

Underlayment

0 rolls

Nails

0 lbs

Estimated Material Cost

Includes 0% waste factor for Gable (Simple)

Roof Pitch Correction Factors

Pitch	Angle	Multiply By
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	30.3°	1.158
8/12	33.7°	1.202
9/12	36.9°	1.25
10/12	39.8°	1.302
11/12	42.5°	1.357
12/12	45°	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°	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

Understanding Roofing Calculations

Roof pitch is the measurement of a roof's vertical rise divided by its horizontal run. In the United States, a run of 12 inches is used, and pitch is measured as the rise over 12 inches.

Roof Pitch Effect

A steeper roof has a larger actual area than its footprint. At 6/12 pitch, area is 11.8% larger; at 12/12, it's 41.4% larger.

Material Lifespans

Asphalt shingles: 15-30 years • Metal: 40-70 years • Tile: 50-100 years • Slate: 75-200 years

Waste Factors

Simple gable roofs: 10% waste • Hip roofs: 15% • Complex shapes: 20% or more

Roofing Squares

Roofing is measured in "squares" - 1 square = 100 square feet. Most estimates are quoted per square.

Roofing Calculator: Estimate Shingles, Materials & Roofing Cost

Replacing or installing a roof is one of the largest home improvement investments. Knowing exactly how many shingles, underlayment squares, and ridge caps you need is critical to budgeting accurately and avoiding costly mid-project supply runs. Our Roofing Calculator estimates all materials based on your roof dimensions and pitch.

Roofing materials are sold by the 'square' – one roofing square equals 100 square feet of roof area. However, because roofs are sloped, the actual roof surface area is always larger than the footprint (the house's floor area). The steeper the pitch, the more materials you need.

This calculator supports gable roofs, hip roofs, shed (single-slope) roofs, and mansard configurations, providing accurate material estimates including waste factors for valleys, hips, and ridges.

Key Roofing Terminology

Roofing Square: The standard unit of roofing material measurement. One square = 100 sq ft of roof area. A typical residential roof requires 20-30 squares of shingles.

Roof Pitch: The steepness of the roof, expressed as a ratio of rise over run. A 4/12 pitch rises 4 inches for every 12 inches of horizontal run. Common pitches range from 3/12 (low-slope) to 12/12 (steep).

Ridge: The horizontal peak where two roof slopes meet. Ridge cap shingles cover this area.

Valley: The internal angle where two roof planes intersect. Valleys require extra material for proper waterproofing.

Underlayment: A water-resistant layer (felt paper or synthetic) installed beneath the shingles, acting as a secondary moisture barrier.

How to Use the Roofing Calculator

Step 1: Enter Base Dimensions: Measure the length and width of your home's footprint (ground-level outline), not the actual roof area.
Step 2: Select Roof Type: Choose gable, hip, shed, or mansard. Each type has different geometry affecting total area.
Step 3: Enter Roof Pitch: Find your pitch using a speed square or smartphone app. A 6/12 pitch is common.
Step 4: Choose Shingle Type: 3-tab shingles cover slightly differently than architectural/dimensional shingles.
Step 5: Review Results: Get total roof area in squares, number of shingle bundles (usually 3 bundles = 1 square), underlayment rolls, ridge cap packs, nails, and more.

Roofing Area Calculation

Pitch Factor

Pitch Factor = √(1 + (Rise/Run)²)

The pitch factor converts the flat footprint area to the actual sloped roof area. A 6/12 pitch has a factor of approximately 1.118.

Actual Roof Area

Roof Area = Footprint Area × Pitch Factor

Multiply the rectangular footprint by the pitch factor to find the true surface area that needs to be covered.

Squares Required

Squares = Actual Roof Area ÷ 100 + 10% Waste

Divide total area by 100 (one square) and add 10% for waste, or up to 15-20% for complex roofs with many valleys and hips.

Frequently Asked Questions About Roofing

How many squares of shingles do I need?

Divide your total roof area (in sq ft) by 100 to get squares. Most homes need 20-30 squares. Always add 10% for waste.

How many bundles are in a square?

Typically, 3 bundles of 3-tab shingles cover one square. Architectural/dimensional shingles may require 4 bundles per square – always check the package.