Roof Replacement Cost Calculator: Squares, Bundles & Price

How to measure without climbing on the roof

You don’t need to go up a ladder to get a good first estimate. Measure the footprint of the house at ground level, outside wall to outside wall, and note how far the eaves stick out past the walls. Most houses have 12–18 in overhangs; gable ends (rakes) are often shorter, so 12 in is a reasonable average if you are unsure.

Next, find the pitch. From inside the attic, hold a level horizontally against a rafter, measure 12 in along the level, then measure straight up to the underside of the rafter. That vertical distance in inches is the rise: 6 in means a 6/12 roof.

The calculator multiplies the plan area by a pitch factor of √(1 + (rise ÷ 12)²). That’s exact for any roof where every plane has the same slope, including both gable and hip roofs; the hips change the shape of the planes but not the total area. Dormers, porches with their own roofs and mixed pitches add area, so measure those separately or pick the “complex” style.

Worked example: a 50 × 30 ft ranch

These are the calculator’s default inputs: a 50 × 30 ft footprint, 12 in overhang, 6/12 pitch, simple gable, architectural shingles, one existing layer to remove, national average prices.

That works out to $400–$600 per square all-in. The same roof in 3-tab shingles comes to about $6,140–$10,230, and standing-seam metal about $18,420–$32,740. If the house had two layers of old shingles, removing the extra layer would add 18.6 squares × $100–$300, or $1,860–$5,581.

Why waste depends on the roof shape

Every cut at a hip, valley or rake edge produces an offcut, and starter strips and ridge caps are extra pieces on top of the field shingles. A plain gable roof has only two rakes and one ridge, so 10% waste is usually enough. Hip roofs add a cut along every hip, hence 15%. Roofs with several valleys, dormers or intersecting wings commonly need 20%. If your roofer quotes a specific waste figure, switch on “Set my own waste %” and enter it.

What moves the price

• Material. The installed ranges per square run from $300–$500 for 3-tab asphalt to $900–$1,600 for standing-seam metal and $700–$2,500 for tile. The comparison table shows all four for your roof.
• Old layers. Typical replacement prices, including the ones used here, already cover tearing off one existing layer. Each additional layer adds $100–$300 per square, and heavy materials like tile cost more to strip. With no old roof to remove (new deck or an overlay), the job often prices somewhat lower than the range shown, and many codes allow only one overlay.
• Pitch and height. Steep roofs (roughly 8/12 and up) and two- or three-story houses need extra safety gear and slow the crew down. Many contractors add a steep-slope charge that this estimate doesn’t include.
• Decking. Rotten or delaminated sheathing is replaced at an extra cost per sheet once the old roof is off. Ask for that unit price in writing before work starts.
• Location. Use the local cost level setting: national averages can be well off in high-cost metros and rural areas.

DIY or hire a roofer?

Re-roofing is one of the riskiest home projects to do yourself: falls are the main hazard, and the enhanced warranties shingle manufacturers offer generally require a certified installer. The material counts here (bundles and underlayment rolls) are still useful for checking a contractor’s quote line by line. If a bid lists far more squares than your estimate, ask how they measured.

What this estimate leaves out

Flashing around chimneys and walls, drip edge, ridge vents, ice-and-water shield in cold climates, gutters, skylights, dumpster fees and permits can all appear as separate items. If you are re-roofing, it’s also a good time to check attic insulation with the insulation calculator or plan new exterior work with the siding cost calculator.

How this calculator works

• Plan area = (length + 2 × overhang) × (width + 2 × overhang), with overhang converted from inches to feet.
• Pitch factor = √(1 + (rise ÷ 12)²). Roof area = plan area × pitch factor.
• Squares = roof area × (1 + waste%) ÷ 100. Bundles = squares × 3, rounded up. Underlayment rolls = area with waste ÷ 1,000, rounded up.
• Cost = squares × installed range × local factor + roof squares × (layers − 1, minimum 0) × tear-off range × local factor.

Assumptions and limitations

• Roof area is the footprint plus overhang on all four sides, multiplied by the pitch factor. This is exact for a simple gable or hip roof with one pitch; dormers and mixed pitches add area.
• Waste is 10% for gable roofs, 15% for hip roofs and 20% for complex roofs with many valleys, unless you set your own.
• Asphalt shingles come 3 bundles per square (100 sq ft). Synthetic underlayment covers 1,000 sq ft per roll, with the same waste allowance for laps.
• Installed prices are national 2026 contractor replacement ranges per square, applied to the squares including waste. Following the cost-guide convention, they include tearing off one existing layer.
• Each existing layer beyond the first is charged at the per-layer tear-off range on the actual roof area (without waste). With no existing layer, the job may price somewhat lower than shown.
• Excluded: decking/sheathing replacement, new flashing, gutters, skylights, ventilation upgrades, permits and steep-slope or multi-story surcharges.

These results are planning estimates, not quotes. Local prices, site conditions and building codes vary, so get written estimates from licensed contractors before you commit to a budget.

Frequently asked questions

Sources and data

• HomeGuide (2026) — average cost to tear off and replace roof
• HomeGuide (2026) — tile roof cost
• GAF — how many bundles of shingles are in a square 63a47862 f7e1
• Home Depot product listing — 5
• Angi — how to measure roof for shingles

Prices are US national ranges reviewed October 2026 (data version 2026.10). A few values are editorial estimates where no single published source exists; the Cost Index marks each one. Read our methodology and editorial policy.