How Many Bundles of Shingles Do I Need?

Bundles = roof squares × 3, plus 10–15% for waste, rounded up. A roofing square is 100 sq ft of roof surface, and most 3-tab and architectural shingles take three bundles per square, so one bundle covers about 33⅓ sq ft. A 2,000 sq ft roof is 20 squares: 60 bundles before waste, or 66 bundles with 10% waste.

Two things trip people up. First, use the roof's sloped surface area, not the house's floor area. Second, starter strip and ridge cap are usually separate products, counted by length. Some heavy designer shingles also come four or five bundles to the square, so check the wrapper of the product you are buying.

Shingle bundle coverage

Always read the wrapper. It prints the coverage per bundle or bundles per square for that exact product. That beats any rule of thumb, including this one.

How to calculate how many bundles of shingles you need

Step 1: Get the roof area

The most accurate number comes from measuring each roof plane (length × width) and adding them up, or from a roof measurement report. If you'd rather not climb on the roof, which is the safer choice, estimate from the ground:

1. Measure the house footprint including overhangs. A long tape or a laser measure both work from the ground. Measure the walls, then add the eave and rake overhang on each side. Example: 40 × 28 ft walls with 1 ft overhangs → 42 × 30 ft = 1,260 sq ft.
2. Multiply by the pitch factor from the table below to convert that flat area into sloped roof surface.

Add separate areas for porches, garage roofs and dormers.

Step 2: Adjust for roof pitch

Pitch is the rise in inches per 12 inches of horizontal run. A 6/12 roof rises 6 in for every 12 in. You can usually read it from the attic: hold a level horizontally against a rafter, measure 12 in along the level, and measure straight up to the underside of the rafter. Or use an angle-finder app from a ladder at the gable end.

The factor is plain geometry: √(12² + rise²) ÷ 12. For example: 1,260 sq ft × 1.118 (6/12) = 1,409 sq ft of roof.

Very low slopes have their own rules. Many asphalt shingle manufacturers require special underlayment below 4/12 and don't allow shingles at all below 2/12. Check the product's installation instructions.

Step 3: Convert to squares

Squares = roof area ÷ 100. In the example: 1,409 ÷ 100 = 14.09 squares.

Step 4: Add waste

Waste covers the shingles you cut off at rakes, hips, valleys and around vents, plus a few damaged pieces.

Example (simple gable): 14.09 × 1.10 = 15.5 squares.

Step 5: Multiply by bundles per square and round up

15.5 × 3 = 46.5 → 47 bundles of field shingles.

Many roofers also keep one or two spare bundles from the same production lot for future repairs. Color can vary between lots, so a spare from the original order will match better later.

How many bundles of shingles per roof size?

At 3 bundles per square, rounded up:

For a 4-bundle product, multiply the squares-with-waste by 4 instead of 3.

Starter strip and ridge cap

These are counted from edge lengths, not area, so don't fold them into the waste percentage.

• Starter strip runs along every eave, and on many roofs up the rakes (gable edges) as well. Add up those lengths and divide by the linear feet per bundle printed on the starter product.
• Hip and ridge cap covers every ridge and hip. Add up those lengths and divide by the cap product's linear feet per bundle. Coverage varies widely between products, so don't guess. A hip roof needs far more cap than a gable roof of the same size.

Example (the 42 × 30 ft gable above): eaves = 2 × 42 = 84 ft; rakes = 4 × about 16.8 ft (half the 30 ft span × 1.118) = about 67 ft; ridge = 42 ft. Buy starter for about 151 linear ft (84 ft if you only run it along the eaves) and ridge cap for 42 linear ft.

Some installers cut 3-tab shingles into starter and cap pieces instead of buying dedicated products. Architectural shingles usually can't be used that way. Follow the shingle maker's instructions, which can also affect the warranty.

What else goes on the order

Shingles are only part of a re-roof. Each of these is counted separately, and their coverage is printed on the product:

• Underlayment (synthetic or felt), by roll coverage
• Ice and water shield along eaves and in valleys, where your code or the climate calls for it
• Drip edge, by linear feet of eaves and rakes
• Roofing nails: the count per shingle is set by the manufacturer, and more are required in high-wind areas
• Vents, pipe boots and flashing
• Tear-off and disposal: if you're removing old layers, plan for dumpster size and weight
• Gutters: a re-roof is a good time to replace tired gutters, since the drip edge and fascia are exposed anyway. Price them with the gutter installation cost calculator, and if you're keeping guards, see how to clean gutters with guards.

Check your local building department before you start. Many places require a permit for a re-roof and limit how many shingle layers a roof can carry.

Common mistakes

• Using the home's square footage. Living area ignores overhangs, garages and pitch, and counts upper floors that don't add roof.
• Forgetting the pitch factor, which can put you several squares short on a steep roof.
• Assuming every shingle is 3 bundles per square. Designer lines are often 4 or 5.
• Adding starter and cap into the waste instead of counting them by length.
• Skimping on waste for a hip roof. Every course is cut at each hip.
• Ordering exactly to the number with no spare from the same lot.

Roof work is dangerous. Falls from roofs are a leading cause of serious construction injuries. If you aren't experienced with ladders and fall protection, measure from the ground or attic and let a roofer verify the takeoff.