Roofing Calculator
Roof area and shingle count from the ground. Enter the footprint of one roof plane, pick the pitch to scale it up the slope, and set the number of planes (2 for a gable, 4 for a hip). A square is 100 ft²; architectural shingles come three bundles to a square. Hips and valleys waste more — use 15%.
Order 42 bundles — order ridge cap separately (≈ 1 bundle per 25–35 lf of ridge and hips).
- Area
- 1,252 ft²
- Waste / cuts 10%
- + 125 ft²
- Coverage to buy
- 1,377 ft²
- Metric
- 116.3 m²
- Bundles (33⅓ ft²)
- 42
- Squares (100 ft²)
- 14
- Approx. weight
- 2,940 lb
- Synthetic underlayment, 10-square roll
- 2 rolls
- Roofing nails, 1¼″ (1 lb ≈ 320)
- 13 lb
- Starter strip, 100 lf bundle
- 2 bundles
- Materials + delivery$30–$55 / bundle · Sep 2026
- $1,360 – $2,410
- Installed (with labor)typ. $5,536
- $3,864 – $8,671
- Architectural shingles, bundle42 bundles
- Synthetic underlayment, 10 sq roll2 rolls
- Roofing nails, 1¼″13 lb
- Starter strip2 bundles
Quantities follow the ticket. Links may earn us a commission at no cost to you; they never change a number.
What will this roofing job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
How to calculate shingles by hand
Roof area = Σ plane footprint × pitch factor · Squares = area ÷ 100 · Bundles = squares × 3, plus waste
Worked example
- One plane: 40 ft × 14 ft = 560 ft² footprint × 1.118 (6/12) = 626 ft².
- Two planes: 1,252 ft² = 12.5 squares.
- Waste 10%: 1,377 ft² → 42 bundles (14 squares).
- Also: 2 rolls of synthetic underlayment, 14 lb of nails, 2 bundles of starter, plus ridge cap for 40 ft of ridge.
- 1 square
- 100 ft² · 3 bundles (architectural)
- Bundle weight
- 65–80 lb
- Pitch factor 4/12 · 6/12 · 8/12
- 1.054 · 1.118 · 1.202
- Ridge cap
- ≈ 1 bundle per 30 lf
Questions crews ask
How many bundles of shingles do I need?
Roof area ÷ 100 gives squares; three bundles per square for architectural shingles, plus 10% for waste and starter. A 40 × 28 ft gable at 6/12 is about 1,250 ft² → 12.5 squares → 42 bundles with waste.
How do I measure a roof from the ground?
Measure the building footprint under each roof plane, multiply by the pitch factor (1.118 for 6/12), and add the planes. Add 1–2 ft of overhang per side. For hips and dormers, break the roof into rectangles and triangles.
What is a roofing square?
100 square feet of roof surface. Shingles are sold by the square in three bundles (architectural) or occasionally four (heavy designer shingles). A 20-square roof is 2,000 ft² and 60 bundles.
How much waste for shingles?
10% for a simple gable, 15% for a hip roof or one with valleys and dormers, 20% for complex roofs. Waste covers cuts at rakes, hips and valleys, starter course and the ridge if you cut your own caps.
How much underlayment and nails?
Synthetic underlayment comes in 10-square (1,000 ft²) rolls; felt in 4-square rolls. Nails: about 320 per pound of 1¼″ roofing nails, four per shingle — roughly 1 lb per square, more in high-wind zones with six nails per shingle.