Roof pitch calculator

You need a number for roof pitch before anyone climbs a ladder, and the roof pitch calculator gives you one. Call (855) 812-6217 during business hours with the result and your ZIP code, and we match the job with licensed roofers who work near you. Quotes cost nothing and you hire only if you want to.

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Enter rise and run and this roof pitch calculator gives the pitch, the angle and the slope factor. Luis measured 6 inches of rise over 12 of run: a 6/12 pitch, 26.6 degrees.

Rise and run

Hold a level flat against the roof or a rafter. Mark 12 inches along it, then measure straight up from that mark to the roof. That height is the rise.

Your pitch and angle

Pitch is written as rise over 12, like 6/12. The angle is the same slope in degrees. Omni Calculator notes that a 30 degree roof is roughly a 7/12 pitch.

How the roof pitch calculator works

The angle is the arctangent of rise divided by run. The slope factor is the length of the sloped line divided by the run. Roofers multiply the flat footprint by that factor to get the real roof area.

The pitch-to-degrees rule matches the Omni pitch calculator.

Roof pitch chart

Pitch, angle and slope factor
Pitch	Degrees	Slope factor
3/12	14.0	1.031
4/12	18.4	1.054
5/12	22.6	1.083
6/12	26.6	1.118
7/12	30.3	1.158
8/12	33.7	1.202
9/12	36.9	1.250
10/12	39.8	1.302
12/12	45.0	1.414

Why steep roofs cost more

A steeper roof has more surface over the same house. At 12/12 the roof is 41% bigger than the footprint. Crews also move slower, use more safety gear, and stage shingles on roof jacks.

Very low roofs bring their own costs. ENERGY STAR treats 2:12 and flatter as low slope, and those roofs need a membrane rather than shingles. See the ENERGY STAR cool roof page for that cutoff.

Can you walk on it

Up to about 4/12 most people can stand on a dry roof. Past 7/12, even roofers tie off. OSHA requires fall protection at six feet of height on construction jobs, per the OSHA fall protection page.

Measure from inside the attic when you can. A rafter gives the same rise and run as the roof.

Worked examples

Luis: 6 inches over 12 gives 6/12, 26.6 degrees, slope factor 1.118.
A porch roof with 3 inches over 12: 3/12, 14.0 degrees, factor 1.031.
A steep Victorian with 12 over 12: 12/12, 45.0 degrees, factor 1.414.

Take the factor to the roofing calculator or the roof size calculator.

Sources

Last checked October 2026

What to do now

Run the calculator with your own footprint, slope and material, and write down low, likely and high.
Call (855) 812-6217 with your ZIP code and the likely number, or send the job below. The Roof Cost Guide team answers during business hours and matches it with licensed roofers near you.
Compare three written quotes line by line against your band before you sign anything.

Talk to a local roofer

Call (855) 812-6217 Call (855) 812-6217

Outside business hours, send the quote form and a roofer calls you back.

Three local quotes, one request

Send the roof pitch calculator job with your ZIP code, roof size and the material you want. Up to three licensed roofers near you quote the same job, and we send your details to them and no one else. Quotes cost nothing and you hire only if you want to.