Shingle Calculator
Estimate asphalt shingle bundles and underlayment from roof dimensions and pitch. Includes waste and cost.
Shingle bundles needed
36
- Roof area with waste
- 1,180.64 sq ft
- Roofing squares
- 11.8
- Bundles (3 per square)
- 36
- Underlayment rolls (400 sq ft)
- 3
- Estimated shingle cost
- $1,260.00
Assumes three bundles per 100 sq ft square and a 10% waste allowance. Starter strips, ridge caps, nails and ice-and-water shield are extra.
Roofing is ordered in squares, and one square is 100 square feet of finished roof. Asphalt shingles typically come three bundles to a square, but the roof area is larger than the building footprint because of the pitch.
This calculator applies a pitch multiplier to the footprint, adds a waste allowance, and converts the result into squares, bundles and underlayment rolls. It does not include starter strips, ridge caps, nails, flashing or tear-off.
How the shingle calculator works
Pitch multiplier = √(1 + (pitch ÷ 12)²). Roof area = building length × width × multiplier × (1 + waste). Squares = roof area ÷ 100. Bundles = squares × 3, rounded up. Underlayment rolls = roof area ÷ 400, rounded up.
Worked example
A 40 × 24 ft building with a 6:12 roof has a footprint of 960 sq ft. The multiplier is 1.118, so the roof area is 1,073 sq ft. With 10% waste that is 1,181 sq ft, or 11.8 squares — 36 bundles and 3 rolls of underlayment.
Roofing squares explained
A square is 100 sq ft of roof surface, not floor area. A 2,000 sq ft house with a 6:12 roof can easily have 2,400 sq ft of roof. That is why material estimates must start from the sloped area or the footprint multiplied by pitch.
Shingle bundles are bulky but light enough for one person to carry. Order all bundles at once from the same lot so the color matches, and keep two or three spare bundles for future repairs.
Shingle types and typical life
| Type | Wind rating | Typical life | Notes |
|---|---|---|---|
| 3-tab | 60–80 mph | 20–25 years | Lightest; fewest design options |
| Architectural | 110–130 mph | 25–30 years | Dimensional look; most common |
| Luxury / designer | 130+ mph | 30–50 years | Heavy; premium price |
| Impact-resistant | Class 3 or 4 | 25–30 years | May qualify for insurance discounts |
What the estimate leaves out
- Starter strip along the eaves and rake.
- Hip and ridge cap shingles.
- Roofing nails, drip edge, valley flashing and pipe boots.
- Ice-and-water shield in cold climates and under valleys.
- Tear-off, disposal, decking repair and labor.
Frequently asked questions
How many bundles of shingles are in a square?
Three bundles per square for standard asphalt shingles. A square covers 100 sq ft of roof, so one bundle covers about 33 sq ft.
How many bundles of shingles for 1,000 square feet?
About 30 bundles for 1,000 sq ft of roof, before waste. With 10% waste, order 33 bundles.
How much shingle waste should I allow?
Ten percent is typical for a simple gable roof. Use 15% for hip roofs, valleys, dormers and complex layouts, and keep a couple of spare bundles.
How many nails per shingle?
Four nails per shingle is common; six in high-wind areas or when the manufacturer requires it. Nails must be placed in the nail line and driven flush, not overdriven.
Can I install new shingles over old ones?
Sometimes, if the old roof is sound and local code allows it. A second layer adds weight and hides decking problems, so tear-off is usually the better choice.
How long do asphalt shingles last?
Three-tab shingles typically last 20–25 years; architectural shingles 25–30 years. Attic ventilation, sun exposure and installation quality matter as much as the product rating.
Assumptions and accuracy
- Dimensions are converted to feet before the calculation; 1 ft = 12 in = 0.3048 m.
- Waste allowances are estimates. Add more for irregular shapes, many cuts and uneven subgrade.
- Bag yields, coverage rates and material densities vary by product. Check the label or ask your supplier.
- Local building codes and site conditions always take precedence over a general-purpose calculator.
- Read our full methodology