A free roofing calculator that turns a footprint and pitch into roof area, squares and bundles of shingles.
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This free roofing calculator works out your roof's area from the house's footprint and the roof's pitch, in squares and bundles of shingles.
It takes rectangles, circles and triangles, so an L-shaped house is 2 rectangles added up.
I built it because a roof is bigger than the ground it covers, and the steeper it is, the bigger the gap.
Here's the formula, a worked example, and how to read a shingle label.
TL;DRKey takeaways
What is a roofing calculator?
A roofing calculator turns a house's footprint and its roof's pitch into the roof's real area.
It gives the area in squares, the unit roofing is sold in, and the bundles of shingles to buy.
How roof area works
A sloped roof is longer than its plan, by the pitch factor. A pitch of 6/12 rises 6 inches for every 12 inches across.
| Pitch | Pitch factor |
|---|---|
| 3/12 | 1.031 |
| 4/12 | 1.054 |
| 6/12 | 1.118 |
| 8/12 | 1.202 |
| 10/12 | 1.302 |
| 12/12 | 1.414 |
IKO's guide defines a square as 100 square feet of roof. It says most popular shingles take 3 bundles a square, but not all, so read the label.
A worked example
Here's the example the calculator loads: a 50 by 30 foot footprint at a 6/12 pitch, 10% extra, and bundles of 33.3 square feet.
1,500 × 1.118 = 1,677 square feet of roof. With 10% extra, that's 1,845. ÷ 100 = 18.4 squares, and ÷ 33.3 = 56 bundles.
Mistakes to avoid
These are the slips that come up most.
- Using the footprint without the pitch factor
- Leaving out the overhangs
- Assuming every shingle takes 3 bundles a square
Who is the roofing calculator for?
It's for anyone pricing a new roof or checking a quote, and these tools help around it.
- Siding calculator – for the walls below
- Square footage calculator – for any footprint
- Paint calculator – for the trim and walls
Know your squares, and every roofing quote is easier to compare.
Plan your money with your AI
Take your numbers further in
Roofing Calculator FAQs
Questions about the roofing calculator? Here's what to know.
A roofing calculator works out a roof's area from its footprint and pitch, in squares and bundles.
Multiply the footprint by the pitch factor, √(1 + (rise ÷ 12)²).
A square is 100 square feet of roof, as IKO's guide defines it.
Most popular shingles take 3 bundles a square, by IKO.
Some take more, so check the label.
The roof rises 6 inches for every 12 inches across.
20 squares, before any extra for cuts.
Yes, set your own share, and it's added before the squares and bundles.
Yes, it's free with no sign-up.
It runs in your browser, and your numbers stay on your device.
I did.
I'm Navid Moazzez, and I made the roofing calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
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