Estimating a roofing job accurately is the skill that separates profitable roofing companies from ones that are always scrambling. Underestimate and you eat the difference. Overestimate and you lose the job. Here's how to build an estimate you can stand behind.
The Basic Formula
Every roofing estimate starts with the same structure:
Total Job Cost = Materials + Labor + Overhead + Profit Margin
Each of those four components has sub-calculations. Get any one wrong and the whole estimate is off. Let's go through each one.
Step 1: Measure the Roof (in Squares)
A roofing square = 100 square feet of roof surface. A 2,000 sq ft house doesn't have a 20-square roof — the actual roof surface is larger because of slope.
Slope factor multipliers (multiply your footprint square footage):
- 4/12 pitch: 1.054
- 6/12 pitch: 1.118
- 8/12 pitch: 1.202
- 10/12 pitch: 1.302
- 12/12 pitch: 1.414
Example: 2,000 sq ft footprint on a 6/12 pitch = 2,000 × 1.118 = 2,236 sq ft = 22.36 squares.
You can get this measurement manually (measuring tape on the roof, or from the ground using a laser), or via satellite measurement tools like the Google Solar API, EagleView, or Hover — which give you facet-by-facet breakdowns automatically.
Step 2: Add Waste Factor
You never install exactly what you measure. Cutting around hips, valleys, dormers, and ridges creates scrap. Standard waste factors:
- Simple gable roof: 10%
- Hip roof: 12–15%
- Complex roof with multiple valleys, dormers, skylights: 15–20%
Apply the waste factor to your square count, then round up to the nearest whole square for ordering.
Example: 22.36 squares × 1.12 (12% waste) = 25.04 → order 26 squares.
Step 3: Calculate Material Costs
A complete roofing material list for a standard asphalt shingle job includes:
- Shingles: 3 bundles per square. Price varies by grade — typically $80–$160/square installed material cost.
- Underlayment (felt or synthetic): 1 roll covers ~4 squares. Synthetic runs $30–$60/roll.
- Ice & water shield: Required at eaves and valleys (and full coverage in cold climates). Price varies $50–$90/square.
- Starter strip: Linear feet of eaves + rakes. One box covers ~100 linear feet.
- Ridge cap: Linear feet of ridge. One bundle covers ~35 linear feet.
- Drip edge: Linear feet of eaves + rakes. Standard aluminum, ~$1.50/linear foot.
- Nails: ~1 box per 10 squares for hand nailing; less for nail guns with coil nails.
- Pipe boots, step flashing, valley metal: Count penetrations and valleys from your measurement.
- Dumpster/disposal: One layer tear-off on a 25-square house is typically 1.5–2 tons of material.
Pull current pricing from your supplier — costs vary by region and fluctuate with material markets.
Step 4: Calculate Labor
Labor is usually your most variable cost. Common methods:
- Per-square rate: A crew that works for $60/square on a 26-square job = $1,560 in labor. Simple, predictable.
- Hourly: A 3-person crew at $25/hour each, working 8 hours = $600/day. Two-day job = $1,200.
- Hybrid: Base per-square rate with modifiers for steep pitch, extra stories, or complexity.
Add pitch modifiers if the roof is steep:
- Up to 6/12: standard rate
- 7/12–9/12: +15–20%
- 10/12+: +25–40%
Also factor in story height: a two-story job takes longer to lift material and is harder to work on safely.
Step 5: Overhead Allocation
Overhead is everything it costs to run your business that isn't tied to a specific job: insurance, vehicles, phones, office rent, software, advertising. Most roofing companies allocate overhead as a percentage of job revenue — typically 15–25%.
If you don't know your overhead percentage, calculate it: add up all your monthly fixed costs and divide by your average monthly revenue. That's your overhead rate.
Step 6: Apply Your Profit Margin
Gross margin targets for roofing:
- Retail residential: 35–50% gross margin
- Insurance restoration: 30–45% (scope is fixed; margin comes from supplements and efficiency)
- Commercial: 25–40% (higher volume, tighter margin)
Gross margin = (Revenue − Direct Costs) ÷ Revenue. This is not the same as markup. A 40% gross margin = a 67% markup on your cost. Many contractors confuse these and underprice their work.
Putting It Together: Example Estimate
26-square hip roof, 6/12 pitch, single-story, one layer tear-off:
- Shingles (26 sq × $95/sq): $2,470
- Underlayment, ice & water, starter, ridge, drip edge: $650
- Flashing, pipe boots, accessories: $180
- Dumpster rental: $350
- Total materials: $3,650
- Labor (26 sq × $65/sq): $1,690
- Overhead (20%): $1,068
- Total costs: $6,408
- 40% gross margin applied (÷ 0.60): $10,680 quote price
That's your floor. Round to a clean number ($10,700 or $10,500) based on your local market. Check your pricing against what comparable jobs in your area are closing at — if you're consistently losing bids, you may be over market; if you're winning every bid, you may be leaving money on the table.
What to Watch Out For
- Don't forget the layers: Tear-off of a second layer costs more in labor and dumpster fees. Price it separately.
- Decking replacement: You don't know how much bad decking you'll find until the old roof is off. Consider a per-sheet allowance in the estimate, or write it as a line item at a set per-sheet rate.
- Permit fees: Include the permit cost in the estimate or specify that it's the homeowner's responsibility.
- Material price locks: Material prices change. If there's a gap between estimate and install, your costs may have moved. Build in a timeframe for your pricing to expire.
Track Actuals vs Estimates
The only way to know if your estimating is accurate is to compare your estimated cost to your actual cost on every job. Most roofing companies don't do this — and that's why they don't know why some jobs are profitable and others aren't. Job costing software that tracks materials ordered, labor hours, and crew pay against the original estimate makes this automatic. Over time, you'll see exactly where your estimates run high and where they run thin.
Further Reading
- Complete Guide to Roofing Estimates — From measurement to signed contract: the full estimating workflow
- Roofing Material Cost Guide — Full line-by-line material takeoff with current price ranges for every component
- Ketterly for Residential Roofing Companies — Estimating, proposals, and job tracking built for residential roofing operations