Estimates for planning only. Always confirm measurements and order a little extra for waste and cuts.
How the roofing calculator works
Roofers and suppliers measure roofs in squares, where one square equals 100 square feet of roof surface. This calculator turns your roof's footprint and pitch into the squares and shingle bundles you'll need, so you can sanity-check a quote or plan a DIY job.
The formula
The math is straightforward once you have two numbers: your roof's footprint (the ground area it covers) and its pitch (how steep it is). A steeper roof has more surface area than its footprint, so we multiply by a pitch factor:
Roof area = footprint × pitch factor × (1 + waste %)
Squares = roof area ÷ 100 · Bundles = squares × 3
Roof pitch factors (multipliers)
Pitch is written as rise-over-run (inches of rise per 12 inches of run). The steeper the pitch, the larger the multiplier:
- Flat / low slope: 1.00
- 4/12: 1.054
- 6/12 (common): 1.118
- 8/12: 1.202
- 9/12: 1.250
- 12/12: 1.414
If you're not sure of your pitch, a 6/12 is the most common residential slope and a safe default for a rough estimate.
Pro tips
- Order 10% extra for a simple gable roof and up to 15% for complex roofs with lots of hips, valleys, and dormers.
- Shingles almost always come three bundles per square. Buy full bundles, not loose shingles.
- Don't forget ridge cap, starter strip, underlayment, drip edge, and nails, this tool sizes the field shingles only.
- Measure the actual roof including overhangs, not just the house footprint.
Frequently asked questions
How many bundles of shingles are in a square?
Three bundles cover one square (100 square feet) for standard architectural shingles. Some premium or designer shingles run four or five bundles per square, so check the wrapper.
How many squares is a 2,000 square foot roof?
It depends on the pitch. A 2,000 sq ft footprint at a common 6/12 pitch is about 22 to 24 squares once you add waste. Flatter roofs need fewer, steeper roofs need more.
Should I include roof overhangs in the measurement?
Yes. Measure the actual roof surface, eaves and overhangs included, not just the floor plan of the house. The overhangs are real roof area that needs shingles.
How much waste should I add?
10% is typical for a simple roof. Add up to 15% for roofs with many valleys, hips, dormers, or for architectural patterns that produce more offcuts.
Is this calculator an exact quote?
No. It's a solid planning estimate. Pitch, layers, tear-off, decking repairs, and accessories all affect the real number, so always get an on-site measurement before ordering.
