Roof Shingle Calculator
Estimate the squares and bundles of shingles for a roof — from the footprint and the pitch.
Last reviewed 2026-06-06
Roofing is priced and sold in “squares” (100 sq ft) and bundles, but you usually start from the building’s footprint. Because a sloped roof has more surface than the ground it covers, you apply a pitch factor — and then add waste for cuts, hips and valleys.
Enter the footprint and choose the pitch; we estimate the roof area, the number of squares, and the bundles of shingles to order.
How to use the Roof Shingle Calculator
- Measure the footprint (length × width of the area the roof covers).
- Choose the pitch — steeper roofs have more surface area.
- Pick a waste allowance (more for hips, valleys and lots of cuts).
- Read the bundles to buy; for a precise order, measure each roof plane.
Frequently asked questions
How many bundles of shingles do I need?
Work out the roof area (footprint × a pitch factor), divide by 100 to get squares, add about 10–15% waste, then multiply by roughly 3 bundles per square. This calculator does it for you.
What is a “square” in roofing?
A square is 100 square feet of roof surface. Shingles, underlayment and labour are all quoted per square. Most architectural shingles need about three bundles to cover one square.
How does roof pitch affect the amount?
A steeper roof has more surface area than its ground footprint. We multiply the footprint by a pitch factor (about 1.06 for low slopes up to ~1.25 for steep ones) to estimate the true roof area.
How much extra should I buy?
Add 10% for a simple gable roof, and 15% or more for roofs with hips, valleys, dormers and lots of cut-in work, where offcuts add up. Keep a spare bundle for future repairs.