Roof pitch is the measure of a roof's steepness, expressed as the ratio of vertical rise to horizontal run over 12 inches. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. It can also be expressed as a decimal (0.5), percentage (50%), or degrees (26.6°).

How do I measure roof pitch from the ground?

Use a speed square or a smartphone app with an inclinometer. From the ground, look at the end of the house (gable end) and estimate the triangle formed by the roof. You can also calculate pitch by measuring rise and run from inside the attic: measure 12 inches along a rafter from the ridge and measure vertically down to the same horizontal level.

What is a normal roof pitch?

Most residential roofs have pitches between 4/12 and 9/12. A 4/12 pitch is considered low-slope, 6/12 is moderate and very common, and 9/12 or steeper is considered steep. Anything below 2/12 is generally considered a flat roof requiring special materials.

How do I convert roof pitch to degrees?

Use the formula: Degrees = arctan(Rise/Run). For a 6/12 pitch: arctan(6/12) = arctan(0.5) = 26.57°. This calculator handles the conversion automatically for any pitch you enter.

What roof pitch is too steep to walk on?

Most roofing professionals consider anything over 7/12 (30.26°) as steep enough to require special equipment and safety harnesses. At 9/12 and above, working without fall protection becomes very dangerous. Some contractors refuse to walk roofs steeper than 12/12 without scaffolding.

Roof Pitch Calculator

Enter rise and run (or any two values) to instantly convert roof pitch between x/12 ratio, degrees, percentage slope, and pitch multiplier.

Enter Any One Value

Pitch Rise (x:12)?

:12

Pitch Angle?

Slope Percent?

Pitch

6.00:12

Moderate Slope

Degrees26.57°

Percent (%)50.0%

Pitch Multiplier1.1180×

Rafter / Ft of Run1.1180 ft

Plumb Cut Angle26.6°

Seat Cut Angle63.4°

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Standard Pitch Reference

Pitch	Degrees	Percent	Multiplier	Rafter/ft
3:12	14.0°	25.0%	1.031	1.031 ft
4:12	18.4°	33.3%	1.054	1.054 ft
5:12	22.6°	41.7%	1.083	1.083 ft
6:12	26.6°	50.0%	1.118	1.118 ft
7:12	30.3°	58.3%	1.158	1.158 ft
8:12	33.7°	66.7%	1.202	1.202 ft
9:12	36.9°	75.0%	1.250	1.250 ft
10:12	39.8°	83.3%	1.302	1.302 ft
12:12	45.0°	100.0%	1.414	1.414 ft

How to Use This Calculator

Enter any two values and the calculator converts to all other formats automatically:

Rise — The vertical height your roof gains, typically measured in inches over a 12-inch horizontal run
Run — The horizontal distance, almost always 12 inches for standard pitch notation
Degrees — The angle of the roof slope from horizontal (0° = flat, 45° = 12/12 pitch)
Percent slope — Rise divided by run, expressed as a percentage (useful for drainage design)

The calculator also outputs the pitch multiplier — the factor you multiply your footprint area by to get actual roof area. Use this with the Roof Area Calculator.

The Formula

Pitch Ratio = Rise : 12 (e.g., 6:12)
Degrees = arctan(Rise / Run) × (180 / π)
Percent Slope = (Rise / Run) × 100
Pitch Multiplier = √(Run² + Rise²) / Run

For a 6/12 pitch:
Degrees = arctan(6/12) = 26.57°
Percent = (6/12) × 100 = 50%
Multiplier = √(144 + 36) / 12 = √180 / 12 = 1.118

Example: Converting a 7/12 Pitch

Example: 7/12 Roof Pitch Conversion

Input Pitch7/12

Rise7 inches per 12 inches run

Degreesarctan(7/12) = 30.26°

Percent Slope58.3%

Pitch Multiplier1.158

ClassificationSteep slope (requires safety harness)

A 7/12 pitch adds 15.8% more area compared to the footprint. A 30×40 ft house with this pitch has 1,200 × 1.158 = 1,390 sq ft of roof area.

Roof Pitch Quick Reference

Pitch	Degrees	% Slope	Multiplier	Category
1/12	4.8°	8.3%	1.003	Flat
2/12	9.5°	16.7%	1.014	Low slope
3/12	14.0°	25%	1.031	Low slope
4/12	18.4°	33.3%	1.054	Moderate
5/12	22.6°	41.7%	1.083	Moderate
6/12	26.6°	50%	1.118	Moderate
7/12	30.3°	58.3%	1.158	Steep
8/12	33.7°	66.7%	1.202	Steep
9/12	36.9°	75%	1.250	Steep
12/12	45.0°	100%	1.414	Very steep

Frequently Asked Questions

Roof pitch is the measure of a roof's steepness expressed as rise over 12 inches of run. A 6/12 pitch rises 6 inches for every 12 horizontal inches. It can also be expressed in degrees (26.6°) or as a percentage (50%).

Hold a level horizontally against a rafter. Mark 12 inches along the rafter from the wall. Measure vertically from the 12-inch mark down to the level. That vertical measurement is your rise. So if it's 5 inches, you have a 5/12 pitch.

Asphalt shingles require a minimum 2/12 pitch (with extra underlayment) or 4/12 for standard installation. Standing seam metal can be installed at 1/2:12 or flatter. Tile requires 2.5/12 minimum. Check your manufacturer's specifications for exact minimums.

Degrees = arctan(Rise/Run). For 6/12: arctan(0.5) = 26.57°. You can use a scientific calculator or this tool to do the conversion instantly.

Pitches up to 6/12 can typically be walked without special equipment on dry surfaces. At 7/12 and above, most professionals use safety harnesses. At 9/12 and steeper, scaffolding or roof jacks are strongly recommended.

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Sources & References

The formulas, code requirements, and reference data used in this calculator are sourced from the following authoritative organizations and publications. Local codes vary — always verify with your jurisdiction's building department.

International Residential Code (IRC) 2024 — Chapter 9: Roof Assemblies — ICC
NRCA Roofing Manual (Steep-Slope & Low-Slope) — National Roofing Contractors Association
Asphalt Shingle Installation Manual — ARMA (Asphalt Roofing Manufacturers Association)
IRC R905.2.2 — Slope Requirements for Asphalt Shingles — ICC
ASTM D3161 / D7158 — Wind Resistance of Roof Coverings — ASTM International

Disclaimer: Calculator results are estimates intended for planning and educational purposes only. They do not replace professional engineering analysis, building permit review, or contractor estimates. Always consult a licensed roofing contractor or structural engineer for final specifications.