Estimating a roofing job is one of those things that looks straightforward until you actually do it. There are a lot of moving parts: roof area, pitch factor, material takeoff, labor pricing, tear-off scope, waste factors, and permits. Miss any one of these and you’re either eating the cost or losing the bid.
I’ve been in the trades for over 20 years. While roofing isn’t my primary trade, I’ve estimated and managed enough roof replacements to know what trips people up. In this guide, I’ll walk you through the complete process of estimating a roofing job, from measuring the roof to delivering a final number. If you want to speed this up, our roofing calculator handles the math, but understanding the process is what separates a contractor who makes money from one who just stays busy.
Step 1: Measure the Roof Area
You can’t estimate what you haven’t measured. There are three ways to get roof measurements:
Method A: Measure from the Ground (Free)
This works for simple roof shapes. Here’s how:
- Measure the building footprint at ground level (length x width of the house)
- Count the pitch by holding a level against the rake (gable end) and measuring the rise over a 12-inch run
- Apply the pitch factor (see table below) to convert flat area to actual roof area
- Add overhangs (typically 1-2 feet on each side)
Roof pitch factor multipliers:
| Pitch | Factor | What It Means |
|---|---|---|
| 3/12 | 1.031 | Nearly flat |
| 4/12 | 1.054 | Low slope |
| 5/12 | 1.083 | Moderate |
| 6/12 | 1.118 | Standard residential |
| 7/12 | 1.158 | Moderate steep |
| 8/12 | 1.202 | Steep |
| 9/12 | 1.250 | Very steep |
| 10/12 | 1.302 | Very steep |
| 12/12 | 1.414 | 45 degrees |
Example: House footprint is 30 ft x 50 ft with 1-foot overhangs on all sides. Pitch is 6/12.
- Adjusted footprint: 32 x 52 = 1,664 sq ft
- Apply pitch factor: 1,664 x 1.118 = 1,861 sq ft of actual roof area
- Convert to squares: 1,861 / 100 = 18.6 squares
Our roof pitch calculator handles the pitch factor math for you.
Method B: Aerial Measurement Services ($15-$50)
Services like EagleView and Hover use satellite imagery to generate detailed roof reports. You get:
- Total roof area
- Each plane measured separately
- Pitch for each section
- Ridge, hip, valley, eave, and rake measurements
- Waste factor recommendations
For complex roofs (multiple planes, dormers, additions), aerial measurements are worth every penny. The accuracy saves you more than the $15-$50 cost.
Method C: Get on the Roof (Free but Physical)
For the most accurate measurements, get up there with a tape measure. Measure each plane as a rectangle or triangle, calculate the area of each, and add them up. This is the old-school method and it’s still the most reliable for roofs where satellite imagery isn’t clear.
Safety note: If the pitch is 8/12 or steeper, don’t walk it without proper safety equipment. Use a harness, roof jacks, or scaffolding. Or just use aerial measurements.
Step 2: Complete Material Takeoff
Once you have the roof area in squares, you need to figure out exactly what materials the job requires. For a detailed quantity guide covering every item from shingles to pipe boots, see the roofing material list. Here’s the full list for a standard asphalt shingle roof replacement:
Shingles
- 3-tab shingles: 3 bundles per square
- Architectural shingles: 3-4 bundles per square (check manufacturer specs)
- Add waste factor: 10% for simple roofs, 15% for complex roofs (hips, valleys, dormers)
Example: 20 squares with 15% waste = 23 squares of shingles = 69-92 bundles depending on type
Underlayment
- Felt (15# or 30#): 1 roll covers ~4 squares (400 sq ft)
- Synthetic underlayment: 1 roll covers 10 squares (1,000 sq ft)
- Ice and water shield: Required in cold climates along eaves (usually 3 feet up from edge). 1 roll covers about 2 squares.
For a 20-square roof: 5 rolls of felt OR 2 rolls of synthetic, plus 2-3 rolls of ice and water shield if required by code.
Drip Edge
- Installed along eaves and rakes
- Measure total linear footage of eaves + rakes
- Standard pieces are 10 feet long
- Add 10% for overlap and waste
Typical 20-square roof: 200-250 linear feet = 22-28 pieces
Ridge Cap
- Shingle ridge cap: covers about 20-25 linear feet per bundle
- Vented ridge cap: buy by linear footage
- Measure total ridge length
Typical 20-square roof: 30-50 linear feet of ridge = 2-3 bundles of ridge cap shingles
Starter Shingles
- Installed along eaves and rakes before the first course
- 1 bundle covers about 100 linear feet
- Measure total eave + rake length
Roofing Nails
- 4-6 nails per shingle (high wind zones require 6)
- 1 box (5 lbs) covers roughly 2-3 squares
- For 20 squares: 7-10 boxes of 1-1/4” coil nails
Vents and Flashing
- Pipe boots: 1 per plumbing vent penetration ($5-$15 each)
- Ridge vent: by the linear foot ($3-$5/ft)
- Step flashing: for walls and chimneys (buy by the piece, $0.50-$2 each)
- Counter flashing: for chimneys ($50-$150 in materials per chimney)
- Valley flashing: metal valleys require W-valley metal ($1-$3/linear ft)
Material Cost Summary (20-Square Roof Example)
| Material | Quantity | Cost Each | Total |
|---|---|---|---|
| Architectural shingles | 69 bundles | $35-$45 | $2,415-$3,105 |
| Synthetic underlayment | 2 rolls | $100-$150 | $200-$300 |
| Ice and water shield | 3 rolls | $90-$130 | $270-$390 |
| Drip edge | 25 pieces | $5-$8 | $125-$200 |
| Ridge cap | 3 bundles | $35-$50 | $105-$150 |
| Starter shingles | 3 bundles | $25-$35 | $75-$105 |
| Nails | 8 boxes | $30-$40 | $240-$320 |
| Pipe boots | 4 | $10-$15 | $40-$60 |
| Ridge vent | 40 LF | $4 | $160 |
| Step flashing | 50 pcs | $1 | $50 |
| Total materials | $3,680-$4,840 |
For a full cost breakdown including all materials and labor, check our roof replacement cost guide.
Step 3: Price the Labor
Roofing labor is typically priced per square. Rates vary by region, complexity, and crew experience.
Labor Rates Per Square
| Task | Rate Per Square |
|---|---|
| Tear-off (1 layer) | $25-$50 |
| Tear-off (2 layers) | $50-$80 |
| Shingle installation | $50-$90 |
| Steep pitch adder (8/12+) | +25-40% |
| Two-story adder | +$10-$20/square |
Flashing and Detail Labor
| Task | Rate |
|---|---|
| Chimney flashing | $150-$300 each |
| Skylight flashing | $100-$250 each |
| Pipe boot installation | $25-$50 each |
| Drip edge installation | $1.50-$3/linear ft |
| Ridge vent installation | $3-$5/linear ft |
For a deep dive on labor pricing, read roofing labor cost per square.
Labor Example (20-Square Roof)
| Item | Calculation | Total |
|---|---|---|
| Tear-off (1 layer) | 20 sq x $40 | $800 |
| Install shingles | 20 sq x $70 | $1,400 |
| Chimney flashing | 1 x $250 | $250 |
| Drip edge | 220 LF x $2 | $440 |
| Ridge vent | 40 LF x $4 | $160 |
| Pipe boots | 4 x $35 | $140 |
| Total labor | $3,190 |
Step 4: Factor in Tear-Off and Disposal
Tear-off is a job within the job. Here’s what it involves:
Tear-Off Costs
- 1 layer of shingles: $25-$50 per square
- 2 layers: $50-$80 per square
- 3 layers: $75-$100+ per square
- Wood shakes or tile: $60-$120 per square (heavier, harder to remove)
Disposal Costs
| Disposal Method | Cost |
|---|---|
| Dumpster rental (20 yard) | $350-$500 |
| Dumpster rental (30 yard) | $450-$650 |
| Dump fees (if self-hauling) | $40-$80 per ton |
Rule of thumb: 1 layer of shingles on a 20-square roof generates about 3-4 tons of debris. A 20-yard dumpster handles most single-layer tear-offs up to 25 squares.
What Adds Weight and Volume
- Multiple layers multiply the debris
- Wood shake is heavier than asphalt
- Rotten decking adds dump fees (and new plywood adds material cost)
- Old flashing, vents, and ridge cap add up
Always include dumpster and disposal in your estimate. It’s a real cost that catches new estimators off guard.
Step 5: Account for Waste
Every roofing job generates waste. Shingles get cut at hips, valleys, rakes, and around penetrations. The more complex the roof, the more waste you produce.
| Roof Type | Waste Factor |
|---|---|
| Simple gable (2 planes) | 10% |
| Standard hip roof | 12-15% |
| Complex (dormers, valleys, multiple levels) | 15-20% |
| Very complex (turrets, steep pitch, many penetrations) | 20-25% |
Apply the waste factor to your shingle order, not your total material list. Underlayment, nails, and flashing don’t need the same waste factor.
Step 6: Don’t Forget Permits
Most jurisdictions require a building permit for a roof replacement. This isn’t optional, and it’s something newer contractors sometimes skip (which can create serious problems for the homeowner down the road).
| Permit Item | Cost |
|---|---|
| Roofing permit | $150-$500 |
| Plan review (if required) | $50-$200 |
| Inspection fees | Usually included in permit |
What Inspectors Look For
- Proper underlayment installation
- Nail pattern and placement
- Flashing at all penetrations and transitions
- Ice and water shield coverage (where required)
- Ventilation meets code
- Drip edge at eaves and rakes
Build the permit cost into your estimate. Some contractors pass it through to the homeowner, others include it in the bid. Either way, account for it.
Putting It All Together: Full Estimate Example
Job: 20-square roof, 6/12 pitch, single story, 1 layer tear-off, 1 chimney, 4 pipe vents, good access
| Category | Amount |
|---|---|
| Materials | |
| Shingles (23 sq with waste) | $3,000 |
| Underlayment + ice/water | $450 |
| Drip edge, ridge cap, starter | $350 |
| Nails, pipe boots, flashing | $400 |
| Ridge vent | $160 |
| Materials subtotal | $4,360 |
| Labor | |
| Tear-off | $800 |
| Installation | $1,400 |
| Flashing + detail work | $990 |
| Labor subtotal | $3,190 |
| Other | |
| Dumpster | $400 |
| Permit | $250 |
| Other subtotal | $650 |
| Job Cost | $8,200 |
| Overhead + Profit (25%) | $2,050 |
| Bid Price | $10,250 |
That’s a realistic bid for a straightforward 20-square re-roof in a mid-range market. Your local rates may be higher or lower.
If you’re not sure how to structure overhead and profit into a roofing estimate, read overhead and profit for contractors before you finalize your number. A lot of contractors build a bid that covers materials and labor and then forget the business costs sitting underneath it all.
Common Estimating Mistakes
Not walking the roof (or at least inspecting it closely). Satellite images don’t show soft decking, multiple layers, or the condition of existing flashing. Get up there or at least inspect from a ladder at multiple points.
Forgetting the pitch factor. A 6/12 roof has 12% more area than the footprint. An 8/12 roof has 20% more. Skip the pitch factor and you’re underestimating materials and labor on every job.
Underestimating tear-off. Two layers doesn’t mean double the time. It means 1.5-2x the time, plus a bigger dumpster, plus more dump fees. Price each layer.
Skipping the waste factor. On a complex hip roof with valleys, you can lose 15-20% of your shingles to cuts. That’s real money.
Not pricing flashing separately. Chimneys, skylights, and wall transitions are labor-intensive. Lump them into “per square” pricing and you’ll underbid every complex roof.
Ignoring permit costs. $200-$500 might seem small, but it adds up across multiple jobs if you’re absorbing it.
Pro Tips for Better Roofing Estimates
Use aerial measurements for complex roofs. The $15-$50 for a satellite report is the best money you’ll spend. The accuracy pays for itself.
Track your actual production rates. Industry averages are a starting point. After 5-10 jobs, you’ll know how fast your crew really works, and your estimates will get tighter.
Separate your line items. Break the estimate into tear-off, installation, materials, disposal, and permits. This makes change orders cleaner and helps the homeowner understand what they’re paying for.
Build in contingency. 5-10% for unknowns. Rotten decking is the most common surprise, and replacing a sheet of plywood mid-job shouldn’t blow up your profit.
Price the job, not just the roof. Consider access, dumpster placement, staging, material delivery logistics, and crew parking. These details affect your actual cost.
FAQs
How much does it cost to replace a roof?
A full roof replacement typically costs $8,000-$15,000 for a standard residential home (15-25 squares). Cost depends on roof size, pitch, material choice, tear-off scope, and local labor rates.
How do I calculate roof squares?
Measure the building footprint (length x width), add overhangs, multiply by the pitch factor, then divide by 100. Example: 1,500 sq ft footprint x 1.118 (6/12 pitch) = 1,677 sq ft / 100 = 16.8 squares. Use our roofing calculator for exact calculations.
How much waste should I add to a roofing estimate?
10% for simple gable roofs, 15% for standard hip roofs, and 20% for complex roofs with valleys, dormers, and many penetrations. Apply the waste factor to shingle quantities.
Do I need a permit for a roof replacement?
In most jurisdictions, yes. Permits typically cost $150-$500 and include inspections during and after the job. Skipping permits can create problems for the homeowner when they sell the house.
How long does a roof replacement take?
A 3-person crew can tear off and install a standard 20-square roof in 2-3 days under good conditions. Steep pitch, multiple layers, or complex rooflines can extend that to 4-5 days.
For the general estimating framework that applies to roofing and every other trade, see our guide on how to estimate construction jobs. If you want to see how all the line items come together in a full construction bid, the construction cost estimator handles the math across trades. And if your markup math needs tightening, the Contractor Markup Calculator helps you convert between markup and margin so your bids hit your profit targets.
Ready to build roofing estimates faster? Try EstimationPro free to turn measurements into complete, professional estimates with materials, labor, overhead, and markup calculated in minutes.
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