Roofing guide

How to Calculate Roof Pitch

To calculate roof pitch, measure how many inches the roof rises over a 12-inch horizontal run. If the roof rises 6 inches over 12 inches, the pitch is 6/12.

Quick answer

Roof pitch = rise / 12-inch run

Example: 6 inches of rise over 12 inches of run = 6/12 pitch.

Want the roof area too? Use the roof pitch calculator →Need the multiplier chart? Open the pitch chart →

What roof pitch means

Roof pitch is the steepness of a roof. In roofing, pitch is usually written as rise over a 12-inch run. A 4/12 roof rises 4 inches for every 12 inches across. A 9/12 roof rises 9 inches for every 12 inches across.

That pitch number matters because it changes the actual roof surface area. A steeper roof has more surface than the flat footprint below it, so pitch affects roofing squares, shingle bundles, underlayment, and other material estimates.

Roof pitch formula

The basic roof pitch formula is simple:

Roof pitch = vertical rise / horizontal run

For standard roofing estimates, set the horizontal run to 12 inches. Then measure the vertical rise. If the rise is 7 inches over a 12-inch run, the pitch is 7/12.

How to calculate roof pitch step by step

Find a safe measuring location. The attic, a gable edge, or an exposed rafter is usually easier and safer than standing on the roof.
Hold a level horizontally. Keep the level flat so your run measurement is horizontal, not angled with the roof.
Measure 12 inches of run. Mark the 12-inch point on the level or use a level that already has ruler markings.
Measure the rise. From the 12-inch mark, measure straight up to the roof line, rafter, or sheathing.
Write the pitch as rise/12. If the rise is 5 inches, the roof pitch is 5/12. If the rise is 8 inches, the roof pitch is 8/12.

Example: calculating a 6/12 roof pitch

Say you hold a level under a rafter and measure a 12-inch horizontal run. From the 12-inch mark, the vertical rise to the rafter is 6 inches.

Run: 12 inches

Rise: 6 inches

Pitch: 6/12

A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance.

How pitch changes roof area

Pitch is not just a label for steepness. It changes how much roof surface you need to cover. If you start with footprint area, you need a pitch multiplier to estimate actual roof area.

Actual roof area = footprint area x pitch multiplier

For example, a 2,000 sq ft footprint with an 8/12 pitch uses a multiplier of about 1.202. The estimated roof area is 2,000 x 1.202 = 2,404 sq ft before waste.

Common roof pitch multipliers

Use this table to see how common roof pitches affect roof area. The example column starts with a 2,000 sq ft footprint.

Pitch	Multiplier	Extra Area %	Example (2,000 sq ft)
4/12	1.054	+5.4%	2,108 sq ft
5/12	1.083	+8.3%	2,166 sq ft
6/12	1.118	+11.8%	2,236 sq ft
7/12	1.158	+15.8%	2,316 sq ft
8/12	1.202	+20.2%	2,404 sq ft
9/12	1.250	+25.0%	2,500 sq ft
10/12	1.302	+30.2%	2,604 sq ft
11/12	1.357	+35.7%	2,714 sq ft
12/12	1.414	+41.4%	2,828 sq ft

Low pitch

A low-slope roof may only add a small amount of surface area, but it still changes the estimate.

Medium pitch

Common pitches like 5/12, 6/12, and 7/12 can add enough area to change roofing squares and bundles.

Steep pitch

Steeper roofs can add a meaningful amount of surface area before waste, accessories, and cut complexity.

Roof pitch vs roof slope

Many people use roof pitch and roof slope to mean the same thing. In everyday roofing estimates, both usually describe rise over run, such as 6/12. If you are reading engineering documents, the terms can be more specific, but for material estimates the practical question is the same: how much does the roof rise over 12 inches of run?

Should you calculate pitch by hand or use a calculator?

Calculate pitch by hand when you need to identify the roof pitch from a rafter, attic, or gable edge. Use a roof pitch calculator when you already have pitch and footprint area and want the next numbers: pitch multiplier, actual roof area, extra area, and roofing squares.

Calculate roof area from pitch →

FAQ

How do I calculate roof pitch?+

Measure the vertical rise over a 12-inch horizontal run. If the roof rises 6 inches over 12 inches, the pitch is 6/12.

What does a 6/12 roof pitch mean?+

A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run.

Can I calculate roof pitch from inside the attic?+

Yes. Measuring from an attic rafter is often safer than measuring from the outside roof surface. Hold the level horizontally against the rafter, measure 12 inches of run, then measure the rise.

Does roof pitch affect shingle estimates?+

Yes. Pitch changes actual roof area. Once you convert footprint area into roof area, you can estimate roofing squares, shingle bundles, and waste more accurately.

Is roof pitch the same as roof angle?+

Not exactly. Pitch is usually written as rise over 12, such as 6/12. Angle is measured in degrees. Roofing estimates usually use pitch because it connects directly to area multipliers.