How to use the roof replacement cost calculator
- Enter the roof size. Squares are best; the roofing calculator gives you squares including waste and can send them here.
- Enter the installed price per square from your quote. The default is only an example.
- Set the tear-off. Choose how many old layers come off and the price per square per layer.
- Add the fixed costs: permit, dumpster, and under Adjust assumptions any decking sheets and other items.
- Compare quotes under Add your prices to see each one per square against your budget.
How the budget is built
Roofing = squares × installed price per square
Tear-off = squares × tear-off price × layers
Decking = sheets × price per sheet
Budget = (roofing + tear-off + decking + permit + dumpster + other) × (1 + contingency)
Worked example
A 15-square roof, one layer off, example prices
- Roofing and tear-off: 15 × ($450 + $60) = $7,650.
- Permit $300 + dumpster $500 = $800, so the subtotal is $8,450.
- 10% contingency = $845, giving a budget of $9,295.
- All-in, that is $9,295 ÷ 15 = $619.67 per square.
What a complete roofing quote includes
| Item | Why it matters |
|---|---|
| Shingle brand and line | Lines differ in weight, wind rating and warranty |
| Underlayment and ice barrier | Synthetic vs felt; ice and water shield at eaves and valleys |
| Tear-off layers | Each layer adds labor and disposal |
| Decking price per sheet | Sets the cost of surprises in advance |
| Drip edge, flashing, vents | Often reused unless the quote says new |
| Permit and inspection | Who pulls it and who pays |
| Cleanup and disposal | Dumpster, magnet sweep for nails |
| Warranty | Manufacturer and workmanship, both in writing |
Common mistakes to avoid
- Using floor area. A 1,500 sq ft house can easily have 18 to 22 squares of roof once pitch and overhangs are included.
- Comparing totals only. Divide by squares and check the contents before choosing the cheapest.
- No decking allowance. Rot shows only after tear-off. Agree a per-sheet price before work starts.
- Forgetting gutters. Old gutters often come off during a reroof. Budget them with the gutter installation cost calculator.
Frequently asked questions
How is a roof replacement priced?
Roofers usually price per square, which is 100 square feet of roof surface. The installed price covers shingles, underlayment, labor and basic accessories. Tear-off of old layers, replacing rotten decking, permits and the dumpster are often listed separately.
How do I find how many squares my roof is?
Use the roofing calculator: enter the house footprint and the pitch, and it gives the roof surface in squares including waste. Floor area is always smaller than roof area because of the slope and the overhangs.
Should I tear off the old roof or overlay?
Tear-off lets the roofer inspect and repair the decking and usually gives a longer-lasting roof. Many codes allow at most two layers of shingles. An overlay costs less now but hides problems and adds weight. Ask your roofer and building department.
How much contingency should a roof budget have?
About 10% is common. Older homes, roofs that have leaked, or roofs with several layers can hide rotten decking, so 15% or a per-sheet decking price in the contract is wise.
How do I compare two roofing quotes?
Divide each total by the number of squares to get a price per square, then check both quotes include the same shingle line, underlayment type, ice and water shield, drip edge, ventilation, tear-off layers, decking price per sheet and warranty.
Does the price per square include waste?
Ask your roofer. Most quotes are based on measured roof squares and the roofer adds waste for cutting and hips. If you enter squares from our roofing calculator, they already include your chosen waste.