Roof Shingle Calculator
Ordering shingles starts with knowing how many bundles your roof needs. This free roof shingle calculator takes your roof's footprint, its pitch, and your waste allowance, then figures out the true sloped roof area, converts it to roofing squares, and rounds up to the whole bundles you'll actually order — including optional ridge cap bundles.
Enter your numbers
Measure the flat footprint of the building (or one roof plane's footprint), not the slope — the calculator adjusts for pitch below.
Both types use the standard 3 bundles per roofing square for estimating.
Your results
| Slope factor | – |
| Actual roof area | – |
| Roofing squares (100 sq ft) | – |
| Bundles with waste included | – |
| Ridge cap bundles | – |
| Total bundles to buy | – |
Bundles are rounded up — you can't buy a partial bundle. Coverage per bundle varies slightly by brand; check the packaging.
How to use this calculator
Measure your roof's length and width at ground level (the flat footprint), in feet. Set the pitch using the slider — a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run, which is a common residential pitch.
Pick your shingle type (3-tab or architectural) — both use 3 bundles per roofing square for estimating — then set a waste allowance. Use 10% for a simple roof, 15% for a roof with hips or dormers, and up to 20% for a complex roof with lots of valleys and skylights.
If you're capping the ridge (and hips), enter the ridge length in feet to get the extra ridge cap bundles. These are separate bundles that cover about 35 linear feet each.
How it works
Roof pitch makes the real surface area bigger than the footprint you measure on the ground. The calculator corrects for this with the slope factor:
slope factor = √(1 + (pitch ÷ 12)²)
For a 6/12 pitch that's √(1 + 0.5²) = √1.25 ≈ 1.118. The actual roof area is length × width × slope factor, and roofing squares are area ÷ 100 (one square = 100 sq ft).
Shingle bundles are sold by coverage: a standard bundle covers about ⅓ of a square, so it takes 3 bundles per square. Waste is added before rounding: bundles = ceil(squares × 3 × (1 + waste%)). Ridge cap bundles are ceil(ridge feet ÷ 35), since a ridge bundle covers roughly 35 linear feet. Bundle coverage varies slightly by brand, so always confirm the square footage per bundle on the packaging before ordering.
Frequently asked questions
How many bundles of shingles are in a square?
A roofing square covers 100 square feet, and as a standard rule of thumb it takes 3 bundles of shingles to cover one square — for both 3-tab and architectural shingles. Some manufacturers package things slightly differently, so check the coverage printed on the bundle wrapper.
How much extra should I order for waste?
Order 10% extra for a simple gable roof, 15% for a moderately complex roof, and up to 20% for a roof with many hips, valleys, dormers, or skylights. Waste comes from cutting shingles to fit around valleys, rakes, and roof penetrations — complex roofs generate far more offcuts.
What's the difference between 3-tab and architectural shingles for coverage?
For estimating, there is none: both 3-tab and architectural (dimensional) shingles take about 3 bundles per roofing square. Architectural shingles are thicker, heavier, and typically last longer, but coverage per bundle is essentially the same across most brands.
How do I calculate ridge cap shingles?
Measure the total linear feet of ridge (plus hips if you're capping those too) and divide by about 35 feet of coverage per bundle, then round up. Ridge caps are sold in separate bundles from field shingles — enter your ridge length above and the calculator adds them automatically.
Does this include starter strips or underlayment?
No. This calculator estimates field shingle bundles and ridge cap bundles only. A real roofing job also needs starter strips along the eaves and rakes, underlayment (felt or synthetic), drip edge, flashing, and nails — plan for those separately with your supplier or roofer.