Roof Pitch Calculator

Free roof pitch calculator: enter rise and run to get the pitch (x/12), the roof angle in degrees, the slope percentage, and the sloped length.

Free, no signup
Formula shown
Rounds up to whole units
Updated October 2026

Rise per 12 units of run

6/12pitch

Angle

26.57°

from horizontal

Slope

50%

rise ÷ run × 100

Slope factor (sloped ÷ horizontal): 1.118
Sloped length for 14 ft run: 15.65 ft

Geometry only. It does not add overhangs or select framing, sheathing, or roofing specifications.

Rise over run, drawn to your pitch

AnswerA rise of 6 in over a run of 12 in is a 6/12 pitch: 26.57° or a 50% slope, so a 14 ft horizontal run measures 15.65 ft along the slope.

How to use this roof pitch calculator

Choose one unit for rise and run. Inches is common: hold a level horizontally, mark 12 in, and measure straight up to the roof surface.
Enter the rise (vertical) and the run (horizontal) you measured.
Enter a horizontal run to convert, such as the horizontal distance from an outside wall to the ridge, to see how long that run is along the slope.
Read the pitch, angle, and slope. The diagram updates to match your ratio.

Roof pitch formula: angle, slope, and length

Pitch, angle, and slope percentage are three ways to describe one ratio: rise ÷ run. Because both numbers are in the same unit, the ratio has no unit. Pitch scales it to a run of 12. The angle is the arctangent of the ratio. The sloped length uses the Pythagorean theorem: for every unit of horizontal run, the surface is √(1 + ratio²) units long.

Default example. A rise of 6 in over a run of 12 in, converting a horizontal run of 14 ft. Change the inputs above and the result panel recalculates; this worked example always shows the default.

Default example arithmetic

Ratio         = rise ÷ run = 6 ÷ 12 = 0.5
Pitch         = 0.5 × 12 = 6 → 6/12
Angle         = arctan(0.5) = 26.5651°
Slope         = 0.5 × 100 = 50%
Slope factor  = √(1 + 0.5²) = 1.118
Sloped length = 14 ft × 1.118 = 15.6525 ft

The sloped length is measured along the roof surface for the horizontal distance you entered. It does not include an overhang or the thickness of any material.

Roof pitch chart: common pitches in degrees

Every pitch from 1/12 to 12/12, computed with the same formula as the calculator. The slope factor is the sloped length for each unit of horizontal run: multiply a horizontal distance or a plan area by it to get the length or area along the roof.

Roof pitch chart
Pitch	Angle	Slope	Slope factor	Sloped length per 10 ft run
1/12	4.76°	8.3%	1.0035	10.03 ft
2/12	9.46°	16.7%	1.0138	10.14 ft
3/12	14.04°	25%	1.0308	10.31 ft
4/12	18.43°	33.3%	1.0541	10.54 ft
5/12	22.62°	41.7%	1.0833	10.83 ft
6/12	26.57°	50%	1.118	11.18 ft
7/12	30.26°	58.3%	1.1577	11.58 ft
8/12	33.69°	66.7%	1.2019	12.02 ft
9/12	36.87°	75%	1.25	12.5 ft
10/12	39.81°	83.3%	1.3017	13.02 ft
11/12	42.51°	91.7%	1.3566	13.57 ft
12/12	45°	100%	1.4142	14.14 ft

Using your roof pitch for area and materials

This calculator measures geometry. It does not order materials or choose structural specifications. Use the results like this:

Roof surface area: multiply a plan (footprint) area by the slope factor (1.118 for the default 6/12) to get the sloped area, then use the coverage on your roofing product's label.
Product limits: roofing products state the slopes they can be installed on. Compare your pitch with the manufacturer's instructions.
Framing: rafter sizes, spacing, and connections depend on spans, loads, and local code. Get those from your plans, an engineer, or the building department.

Tips for measuring roof pitch

Measure rise and run on the roof surface or a rafter, not on a fascia or shingles that may not follow the true slope.
A longer level gives a more accurate reading. With a 24 in level, measure the rise at 24 in and divide both by 2.
Phone inclinometer apps give the angle directly. Convert the angle to pitch with 12 × tan(angle).
Work on roofs only with proper fall protection. Measuring from inside the attic, on a rafter, is often safer.

Roof pitch calculator FAQ

How do I calculate roof pitch?

Measure the vertical rise over a known horizontal run in the same unit, divide rise by run, and multiply by 12. For example, a rise of 6 inches over a run of 12 inches is a 6/12 pitch.

What does a 6/12 roof pitch mean?

The roof rises 6 units for every 12 units of horizontal run. That is a ratio of 0.5, a 50% slope, and an angle of 26.57°.

How do I convert roof pitch to degrees?

Divide the pitch number by 12 and take the arctangent. For 4/12, arctan(4 ÷ 12) = 18.43°. For 12/12, arctan(1) = 45°.

How do I convert degrees to roof pitch?

Multiply 12 by the tangent of the angle. A 30° roof is 12 × tan(30°) = 6.93, so about a 6.9/12 pitch.

What is the difference between pitch and slope percentage?

Both describe rise over run. Pitch states the rise per 12 units of run (6/12). Slope percentage states the rise per 100 units of run (50%). An angle states it in degrees (26.57°).

How do I find the sloped length of a roof from its horizontal run?

Multiply the horizontal run by the slope factor √(1 + (rise ÷ run)²). For a 6/12 pitch the factor is about 1.118, so a 14 ft horizontal run is about 15.65 ft along the slope, before any overhang.

Can I use this to choose rafter sizes or roofing materials?

No. It calculates geometry only. Rafter sizes, spacing, and connections depend on spans, loads, and code requirements. Roofing products state which slopes they can be used on in their installation instructions.

Can I measure rise and run in centimeters or meters?

Yes. Choose any unit, as long as rise and run use the same one. The pitch, angle, and slope are ratios, so they come out the same in any unit.

Calculators

Roofing Calculator — Roof area, roofing squares, and shingle bundles from a footprint and pitch, using the coverage on your shingle wrapper.
Deck Calculator — Decking board count from deck size, actual board width, gap, and board length, with the cutting assumptions shown.
Drywall Calculator — Drywall sheet count for walls and ceilings from room dimensions or total area, minus openings, by sheet size.

Guides

How to Measure an Irregular Area — Split odd shapes into rectangles, triangles, circles, and trapezoids, then average width and depth.

Sources

NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity — National Institute of Standards and Technology. Used for: 1 ft = 0.3048 m (exact); 1 in = 2.54 cm (exact). Checked 2026-10-03.