How to use the Roofing Calculator
- 1
Enter the length and width of the house and the eave overhang.
- 2
Enter the roof pitch and choose gable or hip. Not sure of the pitch? Use the roof pitch calculator first.
- 3
Set the waste factor and, if you like, your installed price per square to get a rough total.
How to calculate roofing squares
A roofing square is 100 square feet of roof. Multiply the footprint including overhangs by the pitch multiplier to get the sloped area, add a waste factor for cuts, ridges and starter rows, then divide by 100.
Example: a 50 × 30 ft house with a 1 ft overhang has a 1,664 sq ft footprint. At a 6/12 pitch that's 1,860 sq ft of roof, and with 10% waste you order 20.5 squares, or 62 bundles of architectural shingles.
Waste factors to use
Waste covers cuts at valleys, hips, rakes and penetrations. Simple roofs waste less; cut-up roofs waste more.
- Simple gable roof: 10%
- Hip roof: 15%
- Roofs with dormers and valleys: 15% to 20%
- Add starter strip and ridge cap separately for exact orders
Frequently asked questions
How many bundles of shingles are in a square?
Three bundles cover one square (100 sq ft) for most architectural and 3-tab shingles. Some heavy designer shingles need four or five.
How many squares is a 2,000 sq ft house?
A 2,000 sq ft single-story house at a 6/12 pitch usually needs about 25 to 28 squares including overhangs and 10% waste. Two stories on the same footprint cover less roof.
How much does a new roof cost per square?
Asphalt shingle replacements commonly run $400 to $700 per square installed, with metal and tile costing more. Tear-off, decking repairs and permits are extra.
How accurate is a footprint estimate?
Good for budgets and first quotes. For orders, use measured or aerial reports, because dormers, valleys and multiple levels add area.
How much underlayment do I need?
Synthetic underlayment usually comes in 10-square (1,000 sq ft) rolls. Low slopes and ice-prone eaves need extra ice and water shield.