Roofing Calculator
Find a roof's area and squares from the house's footprint and pitch, with shingle bundles, underlayment rolls and the cost.
Change the values and press Calculate to work out your own figures.
From the footprint
Enter the building's length and width, the overhang and the pitch.
Show the working
- roof area = footprint × √(1 + (pitch ÷ 12)²)
- squares = roof area ÷ 100
From the footprint area
Enter the building's base area and the pitch.
Show the working
- roof area = footprint × √(1 + (pitch ÷ 12)²)
- squares = roof area ÷ 100
How to use it
Enter the building's length and width, the overhang and the pitch. Enter the building's base area and the pitch.
Lengths can be decimals, fractions or tape entries such as 12' 6 1/2" (in feet or inches). Prices are optional.
Key facts
roof area = footprint × √(1 + (pitch ÷ 12)²) squares = roof area ÷ 100; bundles = squares × 3
Waste
Simple gable roofs need about 10% extra; hips, valleys and dormers 15% or more.
Questions
How many squares is a 1,500 sq ft house at 6/12?
16.77 squares (1,677 sq ft) before waste and overhangs.
How many bundles in a square?
3 bundles of standard shingles.
Formulas
roof area = footprint × √(1 + (pitch ÷ 12)²) squares = roof area ÷ 100; bundles = squares × 3
Sources
Limitations
- Material densities are typical values (the midpoint of the commonly published range); real loads vary with moisture, grading and compaction, so check with your supplier or type in their density.
- Tank results are the geometric volume; real tanks have wall thickness and fittings.