Roof Replacement Calculator — Squares, Bundles & Cost
Estimate a full re-roof. Enter your roof footprint and pitch, pick a material, and the calculator converts to roof area, squares, and bundles, then totals the installed cost — including tear-off, permit, and contingency — with a downloadable estimate PDF.
| Section | Footprint | Roof ft² | Squares |
|---|---|---|---|
| Run the calculator to see your takeoff | |||
How to use the roof replacement calculator
Four quick steps turn your ground footprint and pitch into roof area, squares, and bundles, then a full installed cost — with tear-off, permit, and contingency — and a downloadable estimate.
Pick material & pitch
Choose 3-tab, architectural, or metal, and your roof pitch. The price per square auto-fills — edit to your quote.
Enter the footprint
Add each roof section’s ground length × width. The pitch multiplier converts it to actual roof area — no climbing.
Set tear-off & cost
Choose how many old layers to strip and the rate, then a waste factor, permit, and contingency.
Read results & save a PDF
Get squares, bundles, and the project total, plus a section-by-section takeoff — then download an estimate.
How a roof estimate is calculated
The trick is turning a flat footprint into sloped roof area with a pitch multiplier, then converting to squares, bundles, and cost. Here is the exact math the calculator runs.
Worked example — 40×30 main + 24×24 garage, 6/12 pitch, architectural, 1-layer tear-off, 10% waste
Footprint: 1,200 + 576 = 1,776 ft² · Pitch: ×1.12
Roof area: 1,776 × 1.12 ≈ 1,986 ft² → +10% = 21.8 squares (66 bundles)
Install: 21.8 × $550 ≈ $12,013 · Tear-off: 19.9 sq × $90 ≈ $1,787
Contingency: ($13,800 + $300 permit) × 10% ≈ $1,410
Project total ≈ $15,510 — about 21.8 squares of architectural shingles.
Roofing estimating charts
Handy lookups for pitch multipliers, material prices, squares and cost by footprint, and how the cost stacks. Prices are national-average ballparks — editable, and no substitute for a local quote.
| Pitch (rise / 12) | Multiplier | Adds |
|---|---|---|
| Flat / low | ×1.00 | — |
| 3 / 12 | ×1.03 | +3% |
| 4 / 12 | ×1.05 | +5% |
| 5 / 12 | ×1.08 | +8% |
| 6 / 12 | ×1.12 | +12% |
| 8 / 12 | ×1.20 | +20% |
| 10 / 12 | ×1.30 | +30% |
| 12 / 12 | ×1.41 | +41% |
Multiplier = √(1 + (rise ÷ 12)²). It converts a flat ground footprint to actual sloped roof area.
| Material | Price / square | Notes |
|---|---|---|
| 3-tab asphalt | ~$400 | Basic, shortest life |
| Architectural | ~$550 | Dimensional — most common |
| Metal (standing seam) | ~$1,000 | Premium, long life |
Installed (material + labor) per 100 ft² square. National-average defaults — override with your own quote.
| Footprint | Roof area | Squares | Install @ $550/sq |
|---|---|---|---|
| 1,000 ft² | 1,118 ft² | 12.3 sq | ~$6,765 |
| 1,500 ft² | 1,677 ft² | 18.4 sq | ~$10,145 |
| 2,000 ft² | 2,236 ft² | 24.6 sq | ~$13,530 |
| 2,500 ft² | 2,795 ft² | 30.7 sq | ~$16,910 |
| 3,000 ft² | 3,354 ft² | 36.9 sq | ~$20,290 |
Install cost only — tear-off, permit, and contingency are extra. Steeper pitch or a different material shifts these figures.
| Component | How it’s figured |
|---|---|
| Shingles / install | Squares (with waste) × price per square |
| Tear-off | Squares (net) × layers × rate per square |
| Permit | One-time lump sum |
| Contingency | % of install + tear-off + permit |
| Bundles | ~3 per square, rounded up |
Install uses squares with waste; tear-off uses net squares, since you strip the actual roof, not extra material.
Everything the calculator works out
One footprint and pitch gives you both a materials takeoff and a full cost estimate — everything needed to plan and price a re-roof.
Key figures every roof estimate depends on
Built for planning a re-roof
From a homeowner’s budget to a contractor’s quick quote, the same calculator turns a footprint into squares and dollars.
Planning a re-roof and wants realistic squares and an all-in number before calling contractors.
- Measure the footprint from the ground
- Set the pitch and material
- See squares, bundles & total
Building a quick squares-and-cost estimate for a client with real prices and tear-off.
- Enter your price per square
- Set tear-off layers & rate
- Hand the PDF estimate to the client
Rolling a roof into a larger renovation budget with material and tear-off broken out.
- Model each roof section
- Compare materials by square
- Read install vs extras
7 tips for a realistic roof estimate
A re-roof budget rides on two things: the right roof area and the right add-ons. These habits keep both honest — and it’s a ballpark, not a bid.
Roof replacement calculator FAQ
The measuring, squares, and cost questions people ask most before a re-roof.
Measure the footprint from the ground, then multiply by a pitch factor to get the actual sloped roof area — no climbing.
The pitch factor is √(1 + (rise ÷ 12)²). A 6/12 roof is about 1.12, so a 1,776 ft² footprint becomes roughly 1,986 ft² of roof. Divide by 100 for squares and add ~10% waste.
Add each section — main, garage, porch, dormers — separately. A roofer will measure the actual planes for the final quote.
A roofing square is 100 square feet of roof area. It’s the standard unit roofers use to quote materials and labor.
To convert, divide your total roof area by 100 — a 2,000 ft² roof is 20 squares.
Shingles, underlayment, and installed pricing are all figured per square, so squares (not square feet) are what you order and price.
Most asphalt shingles come three bundles to the square — about 33 ft² per bundle. So a 20-square roof needs roughly 60 bundles.
Some heavier architectural or designer shingles run four or five bundles per square, so check the wrapper.
The calculator uses the common 3-per-square figure, applies your waste factor first, and rounds up so you don’t come up short at the ridge.
Steeper roofs have more surface area than their flat footprint, so pitch directly increases the material you need.
The multiplier is √(1 + (rise/12)²). A 3/12 adds about 3% (×1.03), a 6/12 about 12% (×1.12), and a steep 12/12 about 41% (×1.41). The calculator applies this to your footprint automatically.
Pitch also affects labor — steep roofs are slower and less safe, so contractors often charge more per square.
It scales with roof size, material, and tear-off, so the calculator totals installed price per square plus tear-off, permit, and contingency.
Rough installed figures per square: about $400 for 3-tab, $550 for architectural, and $1,000 for standing-seam metal. A typical ~20-square architectural re-roof with tear-off, permit, and 10% contingency lands in the mid-five figures.
These are national averages that vary widely by region, pitch, and complexity — always get written quotes.
Tear-off is stripping and disposing of the existing roofing down to the deck before the new roof goes on. It’s priced per square, per existing layer — often $75 to $150 a square per layer.
A single layer over a 20-square roof at $90 a square is about $1,800; a double layer doubles that. Removing the old roof lets the crew inspect and repair the decking.
The calculator charges tear-off on the net roof area (no waste) times the number of layers.
A 10% waste factor suits a simple gable roof. Bump it to 15% or more for cut-up roofs with lots of hips, valleys, and dormers, where angle cuts create more offcuts.
Waste covers cuts at hips and valleys, starter and ridge courses, and the odd damaged shingle. Because shingles come in fixed bundles, rounding up protects you from being one bundle short.
Complex roofs also take more labor, so material isn’t the only cost that rises.
Sometimes — an overlay (roof-over) skips the tear-off cost by laying new shingles over one existing layer. Set tear-off layers to 0 in the calculator to price it.
But most codes allow only two total layers, so you can’t overlay a roof that already has two. An overlay also adds weight, hides rotten decking or flashing problems, and typically shortens the new roof’s life.
A full tear-off costs more up front but is usually the better long-term choice. Confirm what your local code allows and what your roofer recommends.
Budget Estimate — Not a Quote: Roof area is estimated from your ground footprint and a pitch multiplier, and the default prices are national-average installed figures that vary widely by material, roof complexity, pitch, height, access, region, and hidden conditions such as rotten decking. This calculator produces a planning-stage takeoff and budget only — it is not a contractor quote, and it does not account for underlayment, flashing, ventilation, decking repair, structural work, or code upgrades beyond the layers and contingency you enter. Measure carefully, confirm what your local code allows, and get written, itemized quotes from licensed roofers before making any decision. For planning purposes only.