Roofing Calculator

Bundles = roof area (the footprint × the pitch’s slope factor) plus 10% ÷ 33.3 sq ft a bundle: a 40 × 28 ft gable roof at 6 in 12 is 1,252.2 sq ft of roof, or 42 bundles of shingles.

Your measurements

Example

Use the unit shown for each box, or type another one: 12 ft 6 in, 150 in, 3.8 m and 600 mm all work, as do the marks on a tape measure.

Roof section 1

Roof shape Footprint length (ft) Footprint width (ft) On a shed roof, the width is the direction the slope runs. Pitch rise, in 12 Overhang past the walls, each side Leave at zero if your length and width already include the overhang.

Measure from Roofing material Sets the coverage and the unit you buy. For metal panels, use the metal roofing calculator. Extra for cuts (%) A simple gable roof wastes the least. Hips, valleys, dormers and many short runs mean more cut shingles, so choose a higher figure. Your shingle supplier can confirm it.

Details Package sizes, prices and materials

Coverage per bundle or tile (sq ft) Filled in from the material above. Change it to the coverage on your product’s label. Your price per bundle or tile ($) Underlayment coverage per roll (sq ft) Total eaves Total rakes Ridges and hips Usable drip-edge length per piece Ridge-cap coverage per bundle Starter-strip coverage per bundle Nails per square Nails per box Decking area to replace (sq ft) Coverage per decking sheet (sq ft) Attic floor area (sq ft) Vent area from your design (sq in) Open area per vent (sq in)

Example: replace these measurements

Your material list

42 shingle bundles+ 5 more items on the list

1,252.2 sq ft measured

Your measured layout

Top view of a gable section: two slopes meet at the ridge line. Length and width include the overhang. Shown section only; not to scale.

Your shopping list

42 shingle bundles
2 underlayment rolls
2 starter-strip bundles
15 drip-edge pieces
2 ridge-cap packs
3,700 roofing nails

Already have some? See what it covers

How many shingle bundles you have

Check a roofer’s number

Squares on the quote

Type the squares a quote lists to compare them with your roof.

Quantities and package details

Sloped roof area: 1,252.2 sq ft
With your cut allowance: 1,377.42 sq ft
Roofing squares: 13.77
Section 1: gable, 6 in 12: 1,120 sq ft footprint × 1.118 = 1,252.2 sq ft (12.52 squares)
Eaves: 80 ft, from the shapes
Rakes: 62.61 ft, from the shapes
Ridges and hips: 40 ft, from the shapes
Underlayment rolls: 2
Starter-strip bundles: 2
Drip-edge pieces: 15
Ridge-cap packs: 2
Roofing nails: 3,700
Replacement sheathing sheets: Enter the area only if decking is replaced
Attic vent area: 538 sq in for a 1,120 sq ft attic: half at the eaves, half at the ridge
Vents to buy: Enter the open area printed on your vent

The calculation

Section 1 (gable): 40 × 28 ft footprint = 1,120 sq ft × 1.118 = 1,252.2 sq ft
1,252.2 × (1 + 10/100) ÷ 33.3333 = 41.32 shingle bundles before rounding.
Underlayment: 1,377.42 sq ft ÷ 1,000 sq ft a roll (GAF FeltBuster, 10 squares a roll) = 1.38, rounded up.
Starter strip along the eaves and rakes: 142.61 ft ÷ 120 ft a bundle (GAF Pro-Start) = 1.19, rounded up.
Drip edge: 142.61 ft ÷ 9.83 ft a piece (10-ft pieces lapped 2 in, as the residential code requires) = 14.5, rounded up.
Ridge cap over the ridges and hips: 40 ft ÷ 25 ft a bundle (GAF Seal-A-Ridge) = 1.6, rounded up.
Nails: 13.77 squares × 264 a square (66 shingles a square, 4 nails each, the maker’s standard pattern; 6 in high-wind areas), rounded up to the next hundred.
Vents: 1,120 sq ft of attic ÷ 300 = 3.73 sq ft (538 sq in) of open vent area when intake and exhaust are balanced; ÷ 150 = 1,076 sq in otherwise (International Residential Code R806.2).

Not measured yet? Common sizes

A rough starting point, worked out with this calculator. Gable roof, footprint including the overhang, 10% extra, 3 bundles per square. A hip roof of the same footprint and pitch needs the same bundles. Use a row to load its size into the calculator, then change it to your measurements.

Shingle bundles by footprint and pitch
Footprint	4 in 12	6 in 12	8 in 12
40 × 25 ft (1,000 sq ft)	35	37	40
50 × 30 ft (1,500 sq ft)	53	56	60
50 × 40 ft (2,000 sq ft)	70	74	80
60 × 40 ft (2,400 sq ft)	84	89	96
70 × 40 ft (2,800 sq ft)	98	104	112

Common questions

How many bundles of shingles are in a square?

Three for the shingles used here. A roofing square is 100 square feet of roof, and GAF’s Timberline HDZ and Royal Sovereign both come three bundles to the square, so one bundle covers about 33 1/3 square feet. Cedar and tile are sold differently; choose them in the material list.

Source: GAF Royal Sovereign shingles: specifications. Listed on the Sources page.

How do I measure a roof without climbing on it?

Measure the house from the ground or take the sizes from plans. The footprint is the roof seen from above: measure the outside walls and enter the overhang in inches, which the calculator adds to every side. Take the pitch from plans or a roofer’s report. You never need sloped measurements.

Does a hip roof need more shingles than a gable roof?

Not for the same footprint and pitch: every plane has the same slope, so the sloped area is the same. A hip roof has more hips to cap and more cut shingles, so choose a higher cut allowance and more ridge caps.

What is the lowest slope for asphalt shingles?

GAF gives 2 in 12 as the absolute minimum. Low slopes also need the maker’s low-slope underlayment details, and a flat section needs a different roof covering altogether.

Source: GAF: Minimum slope for shingles. Listed on the Sources page.

How accurate is a roofing calculator?

This is an estimate. Check the sections, pitch, product coverage and cut allowance before ordering. The count is the footprint times the slope factor, plus your allowance, divided by the bundle coverage. Mistakes come from a missed section, a wrong footprint or a guessed pitch. The calculation panel shows every step so you can check it.

How to plan the quantity

Choose the shape of each roof section and measure its footprint flat, as seen from above. Either measure outside the walls and enter the overhang, or include the overhang in the length and width and leave the overhang at zero. Use the pitch of that section, not the height of the house. A second story does not double the roof footprint.

For the same footprint and pitch, a gable, hip or shed section has the same sloped area. The shape changes the edges: the list totals the eaves, rakes, ridges and hips from each shape for drip edge and ridge caps. Enter your own measured totals in the details to replace them. A gambrel has two slopes on each side, so it asks for the steeper lower pitch and how far the lower slope reaches.

The pitch factor turns the horizontal area into sloped roof area. Add your allowance for cuts, divide by the coverage per bundle, then round up to whole bundles. Starter strips, valley treatment and flashing need their own measured lengths.

Eaves are the lower horizontal edges. Rakes are the sloped outer edges. Enter their combined lengths when you want drip-edge pieces. Use the usable coverage after overlaps, not the full length printed on a piece.

Before you order

This is a roof-covering list. Rotten decking, tear-off, labor, disposal, permits, ventilation and flashing are separate quote items.
Split wings with a different pitch or direction into separate sections. Where two sections meet, the valley is not deducted from their edges; measure valleys, dormers and openings from a plan. Use existing plans or a professional measurement instead of climbing onto a roof.

Have prices moved?

Asphalt roofing products cost 3.9% more in August 2026 than a year earlier (Bureau of Labor Statistics producer price index, preliminary).

What owners paid: the typical roofing job cost $10,000 in the 2023 Census survey.

Plan the work as well as the order: How a roof replacement works: the steps and what to ask your roofer.

Before ordering, read the guide: How many bundles of shingles do I need? Squares, waste and accessories. Or choose another calculator.