FREE ROOFING CALCULATOR
Roofing calculator — squares, shingle bundles, and underlayment from the footprint.
Enter the footprint and pitch. Get roof surface area, squares, bundle counts, and underlayment rolls with waste applied — before you climb a ladder. Free, no signup.
Roof inputs
| Roof surface area | – |
| Area with waste | – |
| Roofing squares | – |
| Shingle bundles (3/square) | – |
| Synthetic underlayment rolls (~10 sq/roll) | – |
| #15 felt rolls (~4 sq/roll) | – |
Estimates only. Field-verify measurements, overhangs, and manufacturer coverage before ordering. Footprint excludes eave overhang — add it to length and width if you want it counted.
Footprint × pitch factor = real roof area
You cannot shingle the footprint — the slope adds surface. Each pitch has a multiplier: √(1 + (rise/12)²). At 6/12 that is 1.118; at 12/12 it is 1.414, over 40 percent more material than the ground plan suggests. Measuring the footprint from the ground and applying the factor is how most residential re-roof quotes get built without a drone or a ladder.
What the bundle count doesn't include
Ridge caps, starter strips, drip edge, ice-and-water shield in valleys and at eaves, flashing, and fasteners all ride on top of field-shingle counts. On a bid, carry them as separate line items so the customer sees the scope — and so a supplier price change on one component doesn't force you to re-figure the whole job.
Calculating quantities is step one. Pricing the whole job is the hard part.
FieldSquire turns a walkthrough — voice notes, photos, measurements — into an editable, line-item estimate with your own labor rates and markup, then sends a branded PDF for signature. Solo plan free for 14 days, no credit card.
Start the free Solo trialFrequently asked questions
How many shingle bundles do I need per square?
Three bundles of standard three-tab or architectural shingles cover one roofing square (100 sq ft). Heavier designer shingles can run four or five bundles per square — check the wrapper coverage before ordering.
How do I calculate roof area from the footprint?
Multiply the building footprint by the pitch factor. A 6/12 pitch has a factor of about 1.118, so a 1,500 sq ft footprint carries roughly 1,677 sq ft of roof surface. The calculator applies the factor for pitches from 2/12 to 12/12.
What waste factor should I use on a roof?
Use 10 percent on simple gable roofs and 15 percent or more on hips, valleys, and cut-up roofs. Waste covers ridge caps, starter courses, and cutting losses.
How many rolls of underlayment do I need?
Synthetic underlayment typically covers about 10 squares per roll; #15 felt covers about 4. The calculator returns both so you can quote either system.
Can this price the whole roofing job?
It returns quantities, not prices. To build a priced roofing bid with tear-off, disposal, flashing, and labor lines, try the FieldSquire roofing estimating app free for 14 days.