Roofing Calculator
Free roofing calculator. Enter your house size and roof pitch to get roof area, squares, shingle bundles, underlayment, drip edge and ridge cap.
10% for simple gables, 15% for hips and cut-up roofs
- Squares
- 20.5
- with waste
- Shingle bundles
- 62
- 3 per square
- Roof area
- 1,860 sq ft
- before waste
- Shingle cost
- $2,480
Accessories
| Synthetic underlayment1,000 sq ft rolls, 10% overlap | 3 rolls |
| Ice and water shieldOne course along the eaves | 2 rolls |
| Drip edge10 ft pieces, eaves and rakes | 18 pcs |
| Starter stripAbout 100 ft per bundle | 2 bundles |
| Hip and ridge capAbout 30 ft per bundle | 2 bundles |
| Roofing nailsAbout 2.5 lb per square | 52 lb |
Price
Architectural shingles usually cost $35–$50 a bundle
$2,480
Shingles only, before tax and delivery
Default prices are typical U.S. retail figures, reviewed November 2026. Enter your supplier's prices for an exact total.
Shingles are sold by the bundle and estimated by the square, which is 100 square feet of roof. Three bundles of standard shingles cover one square. To know how many to buy you need the real roof surface, which is larger than the floor plan because the roof slopes and overhangs the walls.
This calculator takes your house length and width, the eave overhang and the roof pitch, and works out the roof area, squares and bundles. It also estimates underlayment, ice and water shield, drip edge, starter strip and ridge cap so you can price the whole order.
How to use the roofing calculator
- Measure the length and width of the house at the walls, in feet.
- Add the overhang on each side (usually 12 inches).
- Find the pitch: the inches the roof rises over 12 inches of run.
- Multiply the footprint by the pitch multiplier to get the roof area.
- Add 10 to 15% for waste, divide by 100 for squares, and multiply by 3 for bundles.
Roof area = (length + 2 × overhang) × (width + 2 × overhang) × √(1 + (pitch ÷ 12)²). Squares = area × (1 + waste) ÷ 100. Bundles = squares × 3.
Roof pitch multipliers
Multiply the flat footprint (with overhangs) by this number to get the actual roof surface.
| Pitch | Multiplier | Angle |
|---|---|---|
| 3/12 | 1.031 | 14.0° |
| 4/12 | 1.054 | 18.4° |
| 5/12 | 1.083 | 22.6° |
| 6/12 | 1.118 | 26.6° |
| 7/12 | 1.158 | 30.3° |
| 8/12 | 1.202 | 33.7° |
| 9/12 | 1.250 | 36.9° |
| 10/12 | 1.302 | 39.8° |
| 12/12 | 1.414 | 45.0° |
Tips before you buy
- Count each separate roof section (garage, porch, dormers) and add them together.
- Use 10% waste for a simple gable roof and 15% or more for hip roofs with valleys.
- Starter strip and hip-and-ridge shingles are separate products; don't cut field shingles unless the manufacturer allows it.
- Check your local code: many cold-climate areas require ice and water shield at least 24 inches inside the warm wall.
Frequently asked questions
How do you calculate roofing squares?
Find the roof area in square feet, add 10 to 15% for waste, then divide by 100. A 2,000 square foot roof with 10% waste is 22 squares.
How many bundles of shingles do I need?
Most asphalt shingles come three bundles to a square. A 22-square roof needs 66 bundles, plus starter strip and ridge cap bundles.
How many squares is a roof on a 2,000 sq ft house?
For a one-story 2,000 square foot house with a 6/12 pitch and 12 inch overhangs, the roof is roughly 2,400 to 2,500 square feet, or about 27 squares with waste. A two-story house of the same floor area has about half the roof.
How do I find my roof pitch?
Hold a level horizontally against the roof or a rafter, measure 12 inches along it, then measure straight up to the roof surface. That rise in inches is the pitch, such as 6/12.
How many shingles are in a bundle?
A bundle of 3-tab shingles usually holds 26 shingles. Architectural shingles vary by brand, but three bundles still cover about one square.