How many bundles of shingles are in a square?

Three bundles make a square, which covers 100 sq ft of roof. That is the common packaging for 3-tab and architectural shingles, but a few products pack differently, so check the wrapper before you order. The calculator counts 33.3 sq ft per bundle and rounds up.

How do I calculate roof area from the footprint?

Multiply the footprint (length × width of the building, plus the overhang on each side) by the pitch factor, √(1 + (rise ÷ 12)²). For 1,344 sq ft of footprint at 6/12 the pitch factor is 1.118, so the roof is 1,503 sq ft, or 15 squares. The pitch factor table on this page lists 3/12 to 12/12. For a roof of several sections, work out each one and add the bundles, or add the extra ridge length for a dormer or addition.

What is my roof pitch?

Pitch is the rise in inches for every 12 in of run: a 6/12 roof rises 6 in over 12 in across. Hold a level 12 in out from the roof and measure straight down to the roof, or measure from the attic along a rafter. The slope calculator turns an angle, a percent grade or a rise and run into x/12.

How much waste should I allow for shingles?

About 10% for a plain gable roof and 15% for a hip roof or one with many valleys, dormers or short runs, since every cut at a hip, valley or rake leaves offcuts. Both are presets here and you can enter your own. The extra also covers a few damaged shingles and leaves a few spares for later repairs.

How much ridge cap and starter strip do I need?

Ridge cap covers the ridge and every hip: a gable roof has one ridge as long as the roof, a hip roof has a shorter ridge plus four hips. The example gable roof is 42 ft of ridge, so 3 bundles at about 20 ft each. Starter goes along the eaves (84 ft here, 1 bundles at about 100 ft), and some makers also want it along the rakes. Products differ, so check the wrapper.

How many rolls of underlayment do I need?

Divide the roof area by the roll's coverage: about 400 sq ft for a roll of 15 lb felt, 200 sq ft for 30 lb and 1,000 sq ft for most synthetics. The example roof is 1,503 sq ft, so 4 rolls of 15 lb felt. Ice-and-water membrane along the eaves and valleys is bought separately and not counted here.

How many roofing nails do I need?

This is an estimate from the shingle maker's instructions: GAF lists 256 nails per square at the standard 4 nails per shingle and 384 per square where 6 per shingle are required, as in high-wind areas. The example roof, with waste, comes to about 4,232 nails at 4 per shingle. Buy a little extra, since nails are cheap and misfires happen, and use the length and type your shingle's instructions call for.

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

At the same pitch and footprint the area is the same. A hip roof needs more waste, since the hips cut every course on a diagonal, and more ridge cap, because it has four hips as well as a ridge. That is why this calculator offers 15% for hip roofs and counts the hip length.

Do I need a permit or a professional?

Most places require a permit for a full re-roof, and steep or high roofs call for fall protection or a pro. This calculator only counts materials; check local code, including the number of nails and any ice barrier rules for your climate.

Roofing Shingles Calculator: How Many Bundles Do I Need?

A 40 × 30 ft house with a 12 in overhang and a 6/12 gable roof has 1,344 sq ft of footprint, which is 1,503 sq ft of actual roof (footprint × pitch factor 1.118), or 15 squares. With 10% waste it needs 50 bundles of shingles (16.5 squares), 4 rolls of 15 lb felt, 1 bundles of starter strip and 3 bundles of ridge cap. Shingles are commonly packed 3 bundles to the square; check the wrapper.

Figures based on the sources listed belowUpdated 2026-10-03How we calculate

Building length

Building width

Waste

Simple gable roof (10%)Hip roof or many valleys (15%)Custom

Roof pitch (rise per 12 in of run, x/12)

A 6 means the roof rises 6 in for every 12 in across. Use the slope calculator if you only have an angle or a percent. Steep roofs above 12/12 need extra care and safety gear.

Roof shapeSets the ridge, hip, eave and rake lengths for the ridge cap and starter strip. Both shapes have the same area at the same pitch.

Overhang (in)

How far the roof sticks out past the walls, added on every side. Use 0 if the length and width you entered already include it.

Extra ridge or hip length (dormers, additions)

Ridge or hip cap for any part of the roof the length and width do not cover. Leave 0 for a plain gable or hip roof.

Starter strip alongStarter always goes along the eaves; some shingle makers also call for it along the rakes (gable ends). Check the instructions for your shingle.

UnderlaymentRolls are counted on the roof area with no waste, using the coverage printed on the roll. Ice-and-water membrane at the eaves and valleys is not counted.

Nails per shingleManufacturers call for 4 nails per shingle in a standard application and 6 where wind or steep-slope rules require it. Check your shingle and local code.

Price per bundle (optional)

Buy 50 bundles

1,502.64 sq ft + 10% waste = 1,652.90 sq ft

Squares to buy (100 sq ft each, with waste): 17 squares, the roof itself is 15.0 squares
Underlayment (15 lb felt rolls): 4 rolls
Starter strip (bundles of about 100 ft): 1 bundle (≈ 84 ft)
Ridge and hip cap (bundles of about 20 ft): 3 bundles (≈ 42 ft)
Roofing nails, 4 per shingle (estimate): 4,232 nails

Low

$1,400.00

Expected

$1,900.00

High

$2,750.00

Includes 150.26 sq ft waste

How this number is calculated

1,502.64 sq ft + 10% waste = 1,652.90 sq ft ÷ 33.33 sq ft per bundle = 50 bundles

Shopping list

Roofing nails (1-1/4 in, galvanized)
Roofing hatchet or shingle cutter
Coil roofing nailer
Roof harness and rope grab kit
Roofing cement sealant
Chalk line
Utility knife with hook blades
Step flashing

Show diagram

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Pitch factor table: 3/12 to 12/12

Pitch factor = √(1 + (rise ÷ 12)²), worked by this calculator. Multiply the footprint by it for the true roof area. The last column is the squares of roof for each 1,000 sq ft of footprint, before waste.
Pitch (rise in 12)	Angle	Pitch factor	Roof sq ft per 1,000 sq ft of footprint	Squares per 1,000 sq ft of footprint
3/12	14°	1.031	1,031	10.3
4/12	18.4°	1.054	1,054	10.5
5/12	22.6°	1.083	1,083	10.8
6/12	26.6°	1.118	1,118	11.2
7/12	30.3°	1.158	1,158	11.6
8/12	33.7°	1.202	1,202	12
9/12	36.9°	1.25	1,250	12.5
10/12	39.8°	1.302	1,302	13
11/12	42.5°	1.357	1,357	13.6
12/12	45°	1.414	1,414	14.1

Bundles of shingles by footprint and pitch

Gable roof, no overhang, 10% waste, 3 bundles per square, worked by this calculator. Add the overhang to each side first if you measured the walls, and use 15% waste for a hip roof.
Footprint	4/12 pitch	6/12 pitch	8/12 pitch	12/12 pitch
40 × 25 ft (1,000 sq ft)	35	37	40	47
50 × 30 ft (1,500 sq ft)	53	56	60	71
50 × 40 ft (2,000 sq ft)	70	74	80	94
50 × 50 ft (2,500 sq ft)	87	93	100	117

Roofing packaging and coverage used here

Planning figures; products and brands differ, so the wrapper or roll label rules.
Item	Figure used	Note
Shingles	3 bundles per square (100 sq ft)	Common packaging for 3-tab and architectural shingles
15 lb felt underlayment	About 400 sq ft per roll	Counted on roof area with no waste
30 lb felt underlayment	About 200 sq ft per roll	Counted on roof area with no waste
Synthetic underlayment	About 1,000 sq ft per roll	Check the roll: sizes vary
Starter strip	About 100 ft per bundle	Along the eaves, and the rakes if you pick that
Ridge and hip cap	About 20 ft per bundle	Products range, so check the wrapper
Roofing nails (estimate)	256 per square (4 per shingle), 384 (6 per shingle)	From GAF Timberline HD instructions

Methodology & assumptions

Enter the building's footprint (length × width, the plan view from above); the calculator adds the overhang on every side, then multiplies by the pitch factor, √(1 + (rise ÷ 12)²), to get the true area of the sloping surface. That holds for a gable or hip roof when every plane has the same pitch. Squares are the true area ÷ 100 sq ft. Bundles = true area × (1 + waste) ÷ 33.3 sq ft, rounded up, using 3 bundles per square, the usual packaging for 3-tab and architectural shingles; some products (such as some premium or oversize shingles) pack differently, so check the wrapper. The ridge runs along the longer side. A gable roof has a ridge as long as the roof, eaves of twice that, and four sloped rake edges; a hip roof has a ridge of length − width, four hips each (width ÷ 2) × √(2 + (rise ÷ 12)²) long, and eaves all the way around. Ridge cap uses about 20 ft per bundle and starter strip about 100 ft per bundle, conservative planning figures; real products range, so check the wrapper. Underlayment rolls divide the roof area (no waste) by the coverage printed on the roll: about 400 sq ft for 15 lb felt, 200 for 30 lb and 1,000 for synthetic. Nails are an estimate: 256 per square at 4 nails per shingle and 384 at 6, as published for GAF Timberline HD shingles, worked on the squares with waste; the shingle you buy may count differently. Valleys, dormers, ice-and-water membrane, drip edge, flashing and vents are not counted, apart from the extra ridge or hip length you enter. The metric toggle shows lengths in m and the roof area in m².

GAF Timberline HD (HDZ) shingles technical data sheet and application instructions: 3 bundles per square; 4 nails per shingle standard (256 per square), 6 nails per shingle where required for high wind or steep slopes (384 per square)
Asphalt Roofing Manufacturers Association (ARMA), Residential Asphalt Roofing Manual: roofing is measured and sold by the square (100 sq ft of roof)
ASTM D226, asphalt-saturated organic felt used in roofing: Type I (15 lb) and Type II (30 lb) felt; roll coverage comes from the manufacturer label of the roll you buy
Pitch factor √(1 + (rise ÷ 12)²): the slope length of a roof for each unit of horizontal run (the Pythagorean theorem)
Typical US retail prices for architectural shingles, per bundle, 2026 (estimate)

How to calculate roofing shingles

Measure the footprint and overhang. Measure the length and width of the building from above (the plan view) and how far the roof overhangs the walls.
Find the pitch. Measure the rise in inches over 12 in of run, for example 6/12. The slope calculator can turn an angle or percent into x/12.
Get the true roof area. Add the overhang on each side, multiply the footprint by the pitch factor √(1 + (rise ÷ 12)²) and take off skylights and chimneys.
Convert to squares and bundles. Add 10% waste for a gable roof or 15% for a hip roof, divide by 100 for squares and multiply by 3 bundles per square (check the wrapper), rounding up.
Add the trim materials. Count underlayment rolls on the roof area, starter along the eaves, ridge cap along the ridge and hips, and nails per the shingle instructions.

Worked examples

Project	Result
40 × 30 ft house, gable roof, 6/12 pitch, 12 in overhang, 10% waste	50 bundles (1,503 sq ft of roof, 17 squares to buy), 4 rolls of 15 lb felt, 3 bundles of ridge cap
50 × 30 ft house, hip roof, 8/12 pitch, 12 in overhang, 15% waste, 30 lb felt	69 bundles (2,000 sq ft of roof, 23 squares to buy), 10 rolls of 30 lb felt, 120 ft of ridge and hip cap in 7 bundles
28 × 16 ft garage, gable roof, 4/12 pitch, 12 in overhang, 10% waste, one 2 × 4 ft skylight, synthetic underlayment	19 bundles (561 sq ft of roof after the skylight, 7 squares to buy), 1 roll of synthetic underlayment, 2 bundles of ridge cap

Frequently asked questions

How many bundles of shingles are in a square?: Three bundles make a square, which covers 100 sq ft of roof. That is the common packaging for 3-tab and architectural shingles, but a few products pack differently, so check the wrapper before you order. The calculator counts 33.3 sq ft per bundle and rounds up.
How do I calculate roof area from the footprint?: Multiply the footprint (length × width of the building, plus the overhang on each side) by the pitch factor, √(1 + (rise ÷ 12)²). For 1,344 sq ft of footprint at 6/12 the pitch factor is 1.118, so the roof is 1,503 sq ft, or 15 squares. The pitch factor table on this page lists 3/12 to 12/12. For a roof of several sections, work out each one and add the bundles, or add the extra ridge length for a dormer or addition.
What is my roof pitch?: Pitch is the rise in inches for every 12 in of run: a 6/12 roof rises 6 in over 12 in across. Hold a level 12 in out from the roof and measure straight down to the roof, or measure from the attic along a rafter. The slope calculator turns an angle, a percent grade or a rise and run into x/12.
How much waste should I allow for shingles?: About 10% for a plain gable roof and 15% for a hip roof or one with many valleys, dormers or short runs, since every cut at a hip, valley or rake leaves offcuts. Both are presets here and you can enter your own. The extra also covers a few damaged shingles and leaves a few spares for later repairs.
How much ridge cap and starter strip do I need?: Ridge cap covers the ridge and every hip: a gable roof has one ridge as long as the roof, a hip roof has a shorter ridge plus four hips. The example gable roof is 42 ft of ridge, so 3 bundles at about 20 ft each. Starter goes along the eaves (84 ft here, 1 bundles at about 100 ft), and some makers also want it along the rakes. Products differ, so check the wrapper.
How many rolls of underlayment do I need?: Divide the roof area by the roll's coverage: about 400 sq ft for a roll of 15 lb felt, 200 sq ft for 30 lb and 1,000 sq ft for most synthetics. The example roof is 1,503 sq ft, so 4 rolls of 15 lb felt. Ice-and-water membrane along the eaves and valleys is bought separately and not counted here.
How many roofing nails do I need?: This is an estimate from the shingle maker's instructions: GAF lists 256 nails per square at the standard 4 nails per shingle and 384 per square where 6 per shingle are required, as in high-wind areas. The example roof, with waste, comes to about 4,232 nails at 4 per shingle. Buy a little extra, since nails are cheap and misfires happen, and use the length and type your shingle's instructions call for.
Does a hip roof need more shingles than a gable roof?: At the same pitch and footprint the area is the same. A hip roof needs more waste, since the hips cut every course on a diagonal, and more ridge cap, because it has four hips as well as a ridge. That is why this calculator offers 15% for hip roofs and counts the hip length.
Do I need a permit or a professional?: Most places require a permit for a full re-roof, and steep or high roofs call for fall protection or a pro. This calculator only counts materials; check local code, including the number of nails and any ice barrier rules for your climate.

Handy tools

Slope Calculator: Turn a rise and run, an angle or a percent grade into the x/12 pitch the field above takes.
Feet and Inches Calculator: Add up building sides measured in feet, inches and fractions, and get decimal feet for the length and width.