Roof Shingles Calculator
How to Use the Roof Shingles Calculator Enter your house footprint length and width (not the roof area — the floor plan dimensions), select the roof pitch, choose your roof style, select shingle type and waste factor, and optionally include labour. The calculator converts your footprint to actual roof area, then gives you roofing squares, […]
How to Use the Roof Shingles Calculator
Enter your house footprint length and width (not the roof area — the floor plan dimensions), select the roof pitch, choose your roof style, select shingle type and waste factor, and optionally include labour. The calculator converts your footprint to actual roof area, then gives you roofing squares, bundle count, underlayment rolls, ridge cap, and total cost.
1 roofing square = 100 square feet of roof area. Standard asphalt shingles come 3 bundles per square. Always order at least 15% extra — shortages require a second delivery with minimum charges, and batch colour variations make matching difficult.
Understanding Roof Pitch
Roof pitch describes the steepness of a roof as the number of inches of vertical rise per 12 inches of horizontal run. A 6/12 pitch — the most common residential roof — rises 6 inches for every 12 inches of horizontal run. Steeper pitches require more material (there is more actual roof surface per square foot of floor plan) and more labour because the work is harder and slower. A 12/12 pitch is a 45-degree angle and has 41% more surface area than a flat surface of the same footprint. The calculator applies the correct slope multiplier automatically.
Shingle Types and Lifespans
Three-tab asphalt shingles are the entry-level option with a flat appearance and 20–25 year rated lifespan. They are increasingly uncommon as architectural shingles are now available at nearly the same price. Architectural (dimensional) shingles are the current standard — they have a layered, three-dimensional appearance, 30-year warranties, and significantly better wind and impact resistance. Premium impact-resistant shingles (Class 4) carry a 50-year warranty and can reduce homeowners insurance premiums by 20–30% in hail-prone states. Metal roofing (standing seam or metal shingles) has the highest upfront cost but a 50+ year lifespan and near-zero maintenance — the lowest lifetime cost of any roofing option.
FAQs
How many bundles of shingles do I need for a 1,500 sq ft roof?
A 1,500 square foot roof area = 15 roofing squares. At 3 bundles per square (standard architectural shingles), that is 45 bundles for the exact area. Adding 15% waste gives 52 bundles to purchase. Your actual roof area depends on pitch — a 1,500 sq ft house footprint has a larger actual roof area on a steep roof than on a low-pitch roof. Use the calculator above with your house dimensions and pitch for an accurate count.
Should I tear off the old shingles or re-shingle over them?
Most roofing professionals recommend tearing off the old shingles even though it is more expensive. Re-shingling over existing shingles (a “re-roof”) limits you to one additional layer in most jurisdictions, adds weight to the structure, hides damage to the decking that should be addressed, and voids the warranty on most shingle products. Tear-off typically costs $1.50–$2.50 per square foot but allows inspection and replacement of any rotted decking and ensures the new roof installs on a clean, flat surface.