Roof Pitch to Slope Converter

Why convert pitch to slope? Roofers talk in pitch (4/12, 6/12), but building codes, material spec sheets, and engineering reports often use degrees or percent slope. A 4/12 roof is the same thing as an 18.4° slope and a 33.3% slope — this converter does the math so you don't have to, and it works for any rise and run you measure.

Enter the rise and run of your roof in inches, then hit Convert. With the run set to 12 you're using standard pitch notation — 4 rise over 12 run is a 4/12 roof. Controls are sized for comfortable use on a phone.

— /12

Roof pitch ratio — inches of rise per 12 inches of run

Slope in degrees

— °

The roof's angle measured from horizontal (arctangent of rise over run)

Slope in percent

— %

Rise divided by run, times 100 — what engineers and codes call grade

Rise / run ratio

—

The raw ratio behind your pitch, used in rafter tables

Pitch category

—

How roofers classify this slope

How Pitch, Degrees, and Percent Fit Together

Three ways to describe the same triangle. The rise is the vertical leg, the run is the horizontal leg, and the slope is the angle where the roof meets the horizontal.

Degrees = atan(rise ÷ run) × 180 ÷ π
Percent slope = rise ÷ run × 100
Pitch = rise / 12 (inches of rise per 12 inches of run)

Pitch	Degrees	Percent	What it means
1/12	4.8°	8.3%	Nearly flat. Needs a specialized low-slope system — shingles won't work.
2/12	9.5°	16.7%	Minimum slope for asphalt shingles with a proper underlayment.
3/12	14.0°	25.0%	Low but workable. Common on older Oklahoma additions and porches.
4/12	18.4°	33.3%	Very common Tulsa subdivision pitch. Easy to walk, low waste.
5/12	22.6°	41.7%	Slightly steeper — better water shedding, still easy to work.
6/12	26.6°	50.0%	The classic Oklahoma pitch. Great balance of performance and cost.
7/12	30.3°	58.3%	Getting steep. More cut waste on hips and valleys; crews slow down.
8/12	33.7°	66.7%	Steep. Fall protection becomes necessary; expect higher labor costs.
9/12	36.9°	75.0%	Very steep. Roof jacks and harnesses required.
10/12	39.8°	83.3%	Steep-slope territory. Specialized crews and equipment required.
12/12	45.0°	100.0%	A true 45° — the rise equals the run. Specialized steep-slope work.

Why Your Roof's Slope Matters

Once you know your slope in degrees and percent, you can read almost any roofing document — from manufacturer warranties to city code requirements:

Use case	What slope changes
Shingle warranty	Most manufacturers require 2/12 minimum (16.7%) for any coverage, and 4/12 (33.3%) for standard warranty terms on steep slopes.
Code compliance	Building codes specify underlayment and flashing requirements by slope — low-slope roofs need different materials entirely.
Insurance claims	Adjusters describe damage and replacement specs in slope terms. A 6/12 roof (26.6°, 50%) is the most common Oklahoma profile.
Cost & safety	Steeper slopes generate more cut waste and need fall protection. A 10/12 roof (39.8°, 83.3%) can cost 15–30% more to replace than a 4/12.

Need an Expert Read on Your Roof?

Proof Construction LLC gives Tulsa-metro homeowners free, no-obligation roof evaluations. We'll measure your actual pitch, convert it to the slope your paperwork needs, and give you a straight line-item estimate — no sales games.

CALL (918) 734-4444

Licensed & insured • OK License CIB #80004070 • BBB A+ Accredited • Owens Corning Preferred Contractor

Roof Pitch to Slope FAQ

What is the difference between roof pitch, slope degrees, and percent slope?

They are three ways of describing the same angle. Roof pitch is inches of rise per 12 inches of run, written like 4/12. Slope degrees is the actual angle from horizontal — a 4/12 roof sits at 18.4°. Percent slope is the rise divided by the run times 100 — a 4/12 roof is a 33.3% slope. Use this converter to move between all three: degrees = atan(pitch / 12), and percent = pitch / 12 × 100.

How do I convert 4/12 roof pitch to degrees?

Divide the rise by the run (4 ÷ 12 = 0.333), take the arctangent of that ratio, and convert radians to degrees: atan(0.333) × 180 / π = 18.4°. A 4/12 roof is therefore an 18.4-degree slope, which equals a 33.3% slope. This is one of the most common pitches on Tulsa homes.

What is a 6/12 roof pitch in degrees and percent?

A 6/12 roof pitch is 26.6 degrees and a 50% slope. It's the classic Oklahoma pitch: steep enough to shed rain and hail quickly, and safe for a crew to walk without special equipment. It also gives an attic enough height to be usable as storage or living space.

How many degrees is a 12/12 roof pitch?

A 12/12 roof pitch is exactly 45 degrees and a 100% slope — the rise equals the run, so the roof forms a true 45° angle. Pitches at or above 12/12 require specialized steep-slope crews and fall-protection equipment. If you need work done on a steep roof, call Proof Construction LLC at (918) 734-4444.

What roof slope is too low for asphalt shingles?

Standard asphalt shingles need at least a 2/12 pitch (9.5° or 16.7% slope), and most manufacturers recommend 4/12 or steeper for best performance. Anything below 2/12 is low-slope and requires a modified bitumen, TPO, or other specialized low-slope system — shingles on a flat roof will wick water and fail early. Not sure what your roof needs? Proof Construction LLC will measure your pitch and recommend the right system for free — call (918) 734-4444. Explore all roofing solutions from Proof Construction. Measure your roof with the square footage calculator. Count shingles with the shingle count calculator.

Roof Pitch to Slope Converter