Roofing Calculator
Enter your roof dimensions to get the number of squares, bundles of shingles, and a material cost estimate — with waste built in.
How to Calculate Roofing Materials
Roofing is measured in squares — one roofing square equals 100 square feet of roof surface. Shingles are sold in bundles, and most standard shingles take 3 bundles to cover one square.
Step-by-step
- Measure your roof footprint — length × width of your home's outline
- Multiply by pitch factor — a steeper roof has more surface area than its footprint. A 6/12 pitch has ~12% more area than flat.
- Multiply by number of slopes — a standard gable roof has 2 sides
- Add waste — 10–20% depending on valleys, hips, and cut lines
- Divide by 100 to get squares; multiply by 3 to get bundles
Pitch factor reference
| Pitch (rise/run) | Area multiplier | Description |
|---|---|---|
| 3/12 | 1.031 | Low slope |
| 4/12 | 1.054 | Gradual pitch |
| 5/12 | 1.083 | Common residential |
| 6/12 | 1.118 | Medium pitch |
| 7/12 | 1.158 | Moderate-steep |
| 8/12 | 1.202 | Steep |
| 10/12 | 1.302 | Very steep |
| 12/12 | 1.414 | 45° — 41% more area |
If you don't know your pitch, stand in the attic with a level and a tape measure: hold the level horizontal from the rafter, measure 12 inches along the level, then measure straight down to the rafter — that's your rise. A 6" drop over 12" = 6/12 pitch. You can also measure from the ground if you're comfortable reading a speed square on the rake edge.
Roofing Cost Estimates (2026)
Material costs only — labor is separate. Prices vary by region and supplier.
| Shingle type | Cost per square | Expected life |
|---|---|---|
| 3-tab asphalt | $85–$110 / square | 15–20 years |
| Architectural / dimensional | $110–$160 / square | 25–30 years |
| Premium architectural | $160–$220 / square | 30–50 years |
| Metal roofing (standing seam) | $400–$700 / square | 40–70 years |
Don't forget underlayment and accessories
| Item | Coverage / cost |
|---|---|
| Felt underlayment (15 lb) | ~$20–$35 per roll (4 squares) |
| Synthetic underlayment | ~$35–$65 per roll (10 squares) |
| Ice & water shield | ~$65–$100 per roll (2 squares) — eaves + valleys |
| Ridge cap shingles | ~$30–$60 per bundle (35 LF) |
| Roofing nails (1 3/4") | ~$20–$35 per 5 lb box (≈ 2 squares) |
Always order at least one extra square — shingle returns at most lumber yards are easy if the packages are unopened, and running short mid-job means a second delivery minimum charge plus the risk that the new batch is a different manufacturing lot (color variation is real and visible). On a re-roof, also budget for decking repairs — it's common to find rotted sheathing spots once the old shingles are stripped, especially around chimneys and valleys.
Frequently Asked Questions
How many bundles of shingles do I need for a 1,500 sq ft house?
A 1,500 sq ft house footprint with a 5/12 pitch gable roof has roughly 1,500 × 1.083 × 2 sides = 3,249 sq ft of actual roof area. Add 15% waste → 3,736 sq ft ÷ 100 = 37.4 squares. At 3 bundles per square, that's roughly 112 bundles of architectural shingles.
How many squares is my roof?
If you know your roof's footprint (length × width of the house), multiply by 1.1–1.3 depending on pitch, then divide by 100. A rough rule of thumb: your roof is typically about 10–40% larger than your home's square footage, depending on pitch and complexity.
What's the difference between 3-tab and architectural shingles?
3-tab shingles are flat and have a single-layer, uniform appearance — cheaper but typically last 15–20 years. Architectural (dimensional) shingles are thicker, have a layered look that mimics wood shake, and carry 25–50 year warranties. Most new roofs today use architectural shingles — the price difference per square is $20–$50 but the longevity uplift is significant.
How long does a roofing project take?
A standard residential re-roof (strip and replace, 20–30 squares) typically takes 1–2 days for an experienced crew. Complex roofs with multiple valleys, dormers, and high pitch add time. Factor in a day or two of buffer for weather.