Roof Pitch Calculator

Enter the rise and run or the angle of a roof to get its pitch, slope and rafter multiplier. Add the footprint to estimate roof area and squares of shingles.

I know the
Roof pitch
–
Angle–
Slope–
Multiplier–
Type–
Roof area–
Squares (with waste)–

Roof pitch formulas

Pitch = rise ÷ run × 12 (written x/12)
Angle = arctan(rise ÷ run)
Multiplier = √(1 + (pitch ÷ 12)²)
Roof area = footprint × multiplier · Squares = area ÷ 100

Worked example

A roof that rises 6 inches over 12 inches is a 6/12 pitch, an angle of 26.57° and a 50% slope. Its multiplier is √(1 + 0.5²) = 1.118. A 1,500 ft² footprint therefore has about 1,677 ft² of roof, or 18.4 squares with 10% waste.

Roof pitch chart

PitchAngleMultiplier
1/124.76°1.003
2/129.46°1.014
3/1214.04°1.031
4/1218.43°1.054
5/1222.62°1.083
6/1226.57°1.118
7/1230.26°1.158
8/1233.69°1.202
9/1236.87°1.250
10/1239.81°1.302
12/1245.00°1.414
14/1249.40°1.537
16/1253.13°1.667
18/1256.31°1.803

Area estimates assume a simple roof. Dormers, hips and valleys add material, so ask your supplier or roofer to confirm quantities. For the angle of any slope, try the slope calculator or the trigonometry calculator.

Last reviewed October 2026.

Frequently asked questions

What is roof pitch?

Roof pitch is how steep a roof is, written as the inches it rises for every 12 inches of horizontal run. A 6/12 pitch rises 6 inches per foot. The same slope can also be given as an angle (26.6° for 6/12) or a percentage (50%).

How do I measure my roof pitch?

Hold a level horizontally against the roof or a rafter, mark 12 inches along it, and measure straight up from that mark to the roof surface. That measurement is the rise per 12. You can also measure the full rise and run of a rafter and enter both.

What is the roof pitch multiplier?

The multiplier (or slope factor) converts flat footprint area into actual roof surface area. It equals √(1 + (pitch ÷ 12)²). For a 6/12 roof it is 1.118, so a 1,500 ft² footprint has about 1,677 ft² of roof.

What is a roofing square?

Roofing materials are sold by the square, which covers 100 square feet of roof. A 2,000 ft² roof is 20 squares. Add about 10–15% for waste, hips, valleys and starter rows.

What pitch is considered steep?

Pitches under about 4/12 are low slope and may need special underlayment or materials. 4/12 to 9/12 is typical for houses. Above about 9/12 is steep and usually needs extra safety equipment to work on.