Roofing Calculator
Get the roof area and a full materials list from the house's length, width, overhang, pitch and roof style: squares, bundles or metal panels, underlayment, starter strip, ridge cap, ice and water shield, drip edge and nails.
Roof area = footprint with overhangs × slope factor, and a roofing square is 100 sq ft. A 40 × 30 ft house with 1 ft overhangs and a 6/12 gable roof: 42 × 32 × 1.118 = 1,503 sq ft. With 10% waste that is 16.5 squares, or 50 bundles of architectural shingles (3 per square).
Roofing squares by house size and pitch
Gable roof, 1 ft overhangs, 10% waste.
| House | 4/12 | 6/12 | 8/12 | 12/12 |
|---|---|---|---|---|
| 30 × 20 ft | 8.2 | 8.7 | 9.3 | 11.0 |
| 40 × 30 ft | 15.6 | 16.5 | 17.8 | 20.9 |
| 50 × 30 ft | 19.3 | 20.5 | 22.0 | 25.9 |
| 60 × 40 ft | 30.2 | 32.0 | 34.4 | 40.5 |
What goes on a shingle roof
- Underlayment over the whole deck (synthetic rolls cover about 10 squares).
- Ice and water shield along the eaves, in valleys and around chimneys, and at least 24 in inside the warm wall in cold climates.
- Drip edge on eaves and rakes, starter strip along the eaves (and rakes for most brands), then the shingles.
- Ridge cap over ridges and hips, plus ridge vents, pipe boots and step flashing, which this list leaves to you.
Frequently asked questions
How do I calculate how much roofing I need?
Multiply the house's length and width including the overhangs, then multiply by the slope factor for your pitch (1.118 for 6/12). Divide by 100 for squares and add 10–15% for waste.
How many bundles of shingles are in a square?
Three for most 3-tab and architectural shingles; some heavy designer shingles take four or five. One square covers 100 sq ft of roof.
How many squares is a 2,000 sq ft house roof?
A 2,000 sq ft single-story house with a 6/12 roof and overhangs has about 24–26 squares of roof including waste. A two-story house with the same living area has a smaller footprint and about half the roof.
Does a hip roof need more shingles than a gable roof?
For the same footprint and pitch the area is the same, but a hip roof has more cutting and ridge cap, so plan on about 15% waste instead of 10%.
How much does a new roof cost?
Materials for an architectural shingle roof often run $150–$250 per square; installed prices are usually several times that, depending on tear-off, pitch and region. Enter your prices for a materials estimate.
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Related free tools
Roof Pitch Calculator
Pitch, angle, slope factor, rafter length and ridge height from rise and run, width or degrees.
Open tool →Shingle Calculator
Bundles of shingles from measured roof planes, plus starter and ridge cap.
Open tool →Floor Joist Span Calculator
Floor joist span chart and checker for 30 and 40 psf floors.
Open tool →Rafter Span Calculator
Maximum rafter span for roof live load or snow, with or without a ceiling.
Open tool →Sources and assumptions
Roof area uses the slope factor √(1 + (pitch/12)²), exact for roofs whose planes share one pitch. Coverage: 3 bundles per square (4 for heavy shingles), starter about 105 ft per bundle, ridge cap about 25 ft per bundle (brands range 20–33 ft), synthetic underlayment 1000 sq ft per roll, ice and water shield about 65 ft per 3 ft roll, drip edge 10 ft pieces lapped 2 in, 320 nails per square for 4 nails per shingle. Low-slope limits per the Asphalt Roofing Manufacturers Association. Check your product's installation instructions and local code.