Roofing calculator
How many squares is this roof?
You can measure a footprint from the ground. Add the pitch and this works out the real roof area, the number of squares, and the bundles of shingles to order.
Length and width are the outline of the roof seen from above. Nothing you enter is saved or sent.
Most architectural and three-tab shingles come three bundles to the square; some heavier lines take four or more. Check the wrapper. This estimates field shingles only: starter, ridge caps, underlayment and flashing are extra.
How it works
A roofing square is 100 square feet of roof surface. A sloped roof has more surface than the floor area beneath it, and the steeper the pitch, the bigger the difference. Multiply the footprint by a pitch multiplier to get the true area, divide by 100 for squares, then add waste.
Pitch multipliers
| Pitch | Multiplier | Angle |
|---|---|---|
| 3/12 | 1.031 | 14° |
| 4/12 | 1.054 | 18.4° |
| 5/12 | 1.083 | 22.6° |
| 6/12 | 1.118 | 26.6° |
| 8/12 | 1.202 | 33.7° |
| 10/12 | 1.302 | 39.8° |
| 12/12 | 1.414 | 45° |
The multiplier is the square root of 1 + (rise ÷ 12)². For a gable or a hip roof of the same pitch the total surface is the same; what changes is the waste from all the angled cuts.
Finding the pitch
Hold a level flat against the roof or a rafter, mark 12 inches along it, and measure straight down from that mark to the roof. That drop in inches is the rise: 6 inches means 6/12.
From squares to a quote
Shingles are only one line. A roofing price also carries tear-off and disposal, underlayment, drip edge, flashing, vents, ridge caps, nails, and labour that climbs steeply with the pitch. Get the squares right first, then build the rest of the estimate on top.
The quantity is sorted. Now price the job.
ScopeBid: Estimate & Invoice is an offline estimate and invoice app for independent service professionals, on iPhone and iPad. Its listing says Profit Guard shows gross margin and markup side by side before a quote is sent, and each quote goes out as a PDF.
Get ScopeBid on the App StoreYour first three quotes are free with full PDFs. ScopeBid Pro is an optional auto-renewing subscription for unlimited quoting and the wider job-costing and invoicing workflow. Check the App Store for current terms.
Honest Little Apps publishes both ScopeBid and this page. This is a separate browser tool and does not sync with the app. App details checked November 10, 2026.
On a computer? Open it on your iPhone
