Find your roof’s surface area in square feet and roofing squares, corrected for pitch and waste, with the shingle bundles and underlayment you would need to order.
Roofers order by the square of sloped surface. Use the photograph to see where pitch, overhang and waste come from before you check a quote.
The courses, the eave overhang and the samples on the table each matter to the square count and the order.AI-generated illustration for explanation. Not a site inspection, measurement or eligibility record.
The three detail views below enlarge parts of the same photograph. Use them with the checks underneath.
01Shingle courses on the slope
Pitch makes the surface larger
A sloped roof is longer than the plan under it. At 6:12 the surface is about 12% larger than the footprint; at 12:12 it is about 41% larger.
02Eave, fascia and gutter
Include the overhang
The roof extends past the walls. Measure outside wall to outside wall, then add the overhang on each side, usually 12 to 24 inches.
03Shingle samples and bundles
Check bundles per square
Most shingles come three bundles to a square, but some premium products need four or five. Read the bundle label before ordering.
Before you compare roofing quotes, ask for these
Square count
Measured squares before waste, from a report or tape
Waste percentage
The allowance used for hips, valleys and cuts
Pitch
The rise per 12 inches, and any steep-slope surcharge
A roof is almost never flat, so its surface is larger than the footprint of the house under it. The calculator
takes the footprint (including eave overhang), multiplies by a pitch factor, then adds a waste allowance for cuts
and offcuts. The pitch factor is √(1 + (rise/12)²), which is simply the length of the
slope for every 12 inches of horizontal run.
The roof surface is longer than the floor plan under it. The steeper the pitch, the larger the multiplier.
Pitch
Angle
Grade
Multiplier
Notes
1:12
4.8°
8%
1.003
Not for shingles; low-slope membrane
2:12
9.5°
17%
1.014
Shingles generally not allowed below 2:12
3:12
14.0°
25%
1.031
Low slope, needs rated underlayment
4:12
18.4°
33%
1.054
Walkable, common on ranches
5:12
22.6°
42%
1.083
6:12
26.6°
50%
1.118
The most common residential pitch
7:12
30.3°
58%
1.158
8:12
33.7°
67%
1.202
Steeper, slower to work on
9:12
36.9°
75%
1.250
Steep-slope surcharge often starts here
10:12
39.8°
83%
1.302
11:12
42.5°
92%
1.357
12:12
45.0°
100%
1.414
45°, very steep
14:12
49.4°
117%
1.537
16:12
53.1°
133%
1.667
18:12
56.3°
150%
1.803
Mansard-style, specialist work
Roof pitch correction factors. Multiply the footprint by the multiplier to get roof surface area before waste. Grade is rise ÷ run as a percentage.
What a roofing square is
Roofers price and order in squares: one square is 100 square feet of roof surface. A 2,000 sq ft
one-story house with a 6:12 roof has about 22.4 squares of surface, and about 25.7 squares to order with 15% waste. Most
shingles come three bundles to a square, so that roof needs about 78 bundles. Some architectural and premium
shingles need four or five per square, so check the label before you order.
A plain gable roof can get by on 10%. Hips, valleys, dormers and chimneys push it toward 15% to 20%, and a cut-up
roof with many planes can reach 25%. Ordering a little over is cheaper than a second delivery, and leftover bundles
are useful for later repairs.
Measuring without climbing
Measure the house outline at ground level, or take the length and width from your plans.
Check the pitch from inside the attic: hold a level against a rafter, measure 12 inches along it, and read the vertical drop.
Add garage, porch and dormer roofs as extra area, or switch to the roof-planes method and measure each plane.
Cross-check against a satellite measurement report or the contractor’s written measurements, and ask them to explain any difference of more than a square or two.
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Questions
How do I calculate roof area from house square footage?
Divide the living area by the number of stories to get the footprint, then multiply by the pitch factor. For a 2,000 sq ft one-story house with a 6:12 roof the footprint is 2,000 sq ft, the multiplier is 1.118, and the roof surface is about 2,236 sq ft, or 22.4 squares, before waste.
How many squares is a 2,000 sq ft house roof?
A one-story, 2,000 sq ft house with a 6:12 roof is about 22.4 squares, or 25.7 squares to order with a 15% waste allowance. A two-story house of the same size has a smaller footprint and so a smaller roof.
How many bundles of shingles are in a square?
Most asphalt shingles come three bundles to a square. Some architectural and premium shingles are packed four or five to a square, so read the bundle label for the product you are buying.
How much waste should I add when ordering shingles?
About 10% for a simple gable roof, 15% for a typical roof, 20% or more for hips, valleys and dormers, and up to 25% for a heavily cut-up roof. Your installer will usually confirm the quantity.
How do I measure roof pitch?
Hold a level horizontal against a rafter or the underside of the roof deck, measure 12 inches along the level, and measure the vertical distance up to the rafter. That rise per 12 inches of run is the pitch, such as 6:12.
How do I convert roof pitch to degrees?
Divide the rise by 12 and take the arctangent. A 6:12 pitch is about 26.6 degrees, 4:12 about 18.4 degrees and 12:12 exactly 45 degrees. The pitch table on this page lists the angle, the grade and the area multiplier for every pitch from 1:12 to 18:12.
Is roof area the same as the size of my house?
No. The roof also covers eave overhangs and garages or porches, and the sloped surface is larger than the floor area under it. A steeper pitch means a bigger multiplier, so two houses of the same size can have noticeably different roof areas.
How to use this result
Measured area from a calculator is only as good as the inputs. Treat the quantities as an order check and ask your contractor for written measurements. Material costs here use the same installed rates as the roof calculator and exclude tear-off, decking repair, permits and regional labor.
Evidence trail
Sources used to check this tool
Roof area is geometry, and the quantities follow common shingle packaging. Cost rates come from the ReplaceCost roof model documented in the methodology.
These organizations do not endorse ReplaceCost. The written policy, program rules, contractor scope and applicable law control the real result. See the full methodology for the source hierarchy and update process.
Roof measurement
Measure the roof before you price it
Squares, pitch and waste decide how much material a roofer should be ordering.
Roofing squaresOne square is 100 sq ft of roof surface; contractors price by the square.
Pitch multiplierA steeper slope increases surface area for the same footprint.
Waste allowanceHips, valleys and dormers raise the quantity to order.
Bundles and underlaymentConvert squares to bundles, cap, starter and underlayment rolls.
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Planning summary: Start with the physical replacement estimator, then run the Claim gap tool with the replacement figure, item age, expected life and deductible from your declarations page. The result is a planning estimate — not a contractor quote or coverage decision.
