Roofing Calculator
Roof area, shingle squares and bundles from a footprint and pitch.
Roof Preview
6/12 pitchThese are example numbers. Tap any field below and enter your own measurements — every result updates instantly as you type.
Enter the footprint the roof covers — the building length and width, including eave overhangs — then set the pitch.
Extra for starter course, ridge cap and hip/valley cuts — 10–15% is typical.
Optional — material or installed cost per roofing square.
Estimate
Live Material Cost
Tools for this job
SponsoredGear we'd reach for on this job. As an Amazon Associate, BuildCalc earns from qualifying purchases — at no extra cost to you.
Estimates assume every roof plane shares one pitch. Order one extra bundle, and confirm against a supplier take-off before buying.
How the roofing calculator works
BuildCalc's roofing calculator turns two measurements — the footprint the roof covers and its pitch — into a full material take-off. It multiplies the footprint area by the pitch multiplier to get the true sloped area, then converts that into roofing squares, shingle bundles and underlayment rolls.
Roofing is sold by the square — 100 square feet — with three bundles of shingles to a square. A waste factor of 10 to 15 percent covers the starter course, ridge cap and cut-off at hips and valleys, and is folded into every total. Because all sloped planes of one pitch scale the same way, the same calculation works for gable, hip and shed roofs alike.
Guides
- How many bundles of shingles for 1,000 sq ft? — math, a table by shingle type, and what else to buy with them.
- How to figure roof pitch — rise-over-12, converting to degrees, and the pitch multiplier for material take-offs.
Roofing calculator FAQ
How many bundles of shingles do I need?+
Most shingles — three-tab and standard architectural — come three bundles to a roofing square, and a square covers 100 square feet of roof. Find your roof area, divide by 100 for the square count, then multiply by three for bundles. BuildCalc does this for you and rounds up to whole bundles with your waste factor included.
What is a roofing square?+
A roofing square is 100 square feet of roof surface. Shingles, underlayment and labor are all quoted by the square, so it is the unit every roofing estimate is built on.
How does roof pitch change the amount of material?+
A steeper roof has more surface area than the footprint it sits on. BuildCalc multiplies the footprint area by the pitch multiplier — the square root of the pitch squared plus 144, divided by 12. A 6/12 roof has a multiplier of about 1.118, so it needs roughly 12 percent more material than a flat area of the same footprint.
Does this work for a hip or shed roof?+
Yes. For any roof whose planes share one pitch — gable, hip or shed — the total sloped area equals the horizontal footprint area times the pitch multiplier. Enter the footprint the roof covers and the calculator handles all three.
How much waste should I add for a roofing job?+
A waste factor of 10 to 15 percent is standard. It covers the starter course, ridge cap, and cut-off at hips and valleys. Simple gable roofs lean toward 10 percent; complex roofs with several hips and valleys lean toward 15 percent or more.
How do I measure my roof footprint?+
Measure the length and width of the building at the eaves, including any overhang past the walls. That outline is the footprint the roof covers. You do not need to climb on the roof — the calculator converts the flat footprint to true sloped area using the pitch.