Roofing Calculator

Calculate how many shingles, bundles, and roofing materials you need. Get accurate square footage, material lists, and cost estimates for your roofing project.

Roofing Materials

Roof Area

1342 sq ft

Actual sloped area

Squares

14.8

100 sq ft each

Bundles Needed45 bundles
Drip Edge14 pieces
Est. Total Cost$4600

Roof Type

Two sloped sides meeting at a ridge - most common residential roof.

Roof Dimensions

%

Materials Needed

Shingle Bundles45 bundles
Starter Strip2 rolls
Drip Edge (10 ft pcs)14 pieces
Roofing Felt/Underlayment15 rolls
Roofing Nails4723 nails (~19 lbs)
Ridge Cap Length40 linear ft

Cost Estimate

Shingles (~$100/square)$1476
Other Materials$2017
Labor (~$75/square)$1107
Estimated Total$4600

* Estimates based on architectural shingles. Prices vary by region, material quality, and contractor. Does not include tear-off, disposal, or structural repairs.

How It's Calculated

1. Base Area

40 ft × 30 ft = 1200 sq ft

2. Pitch Multiplier (6/12)

1 / cos(arctan(6/12)) = 1.118

3. Actual Roof Area

1200 × 1.118 = 1342 sq ft

4. With 10% Waste

1342 × 1.10 = 1476 sq ft = 14.8 squares

Roof Pitch Reference

PitchAngleMultiplierWalkable?
2/129.5°1.014Easy
4/1218.4°1.054Easy
6/1226.6°1.118Moderate
8/1233.7°1.202Caution
10/1239.8°1.302Difficult
12/1245.0°1.414Difficult

Frequently Asked Questions

Measure the length and width of each roof section at ground level, then multiply by the pitch factor. For a gable roof, measure the base footprint. The pitch multiplier converts flat area to actual sloped area. Use satellite imagery or climb up safely to verify.
A roofing square equals 100 square feet of roof area. Materials like shingles are sold by the square. Three bundles of standard 3-tab shingles typically cover one square. Architectural shingles may require 4-5 bundles per square.
Add 10-15% for simple gable roofs, 15-20% for complex roofs with valleys and dormers. Hip roofs need more waste due to angled cuts. First-time DIYers should add an extra 5-10%. Better to have extra than run short mid-project.
Roof pitch is the slope expressed as rise over run. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Higher pitches shed water and snow better but are harder to walk on and require more materials.
3-tab shingles: 15-20 years. Architectural/dimensional shingles: 25-30 years. Premium architectural: 30-50 years. Metal roofing: 40-70 years. Lifespan depends on climate, ventilation, installation quality, and maintenance.