BYTETOOLS

Roof Pitch Calculator

Convert roof pitch between rise/run ratio, degrees and slope percent, and get the rafter length from the Pythagorean theorem in feet or metres.

6:12
Pitch (x:12)
26.57°
Angle
50%
Slope
13.4164
Rafter length (ft)

Details

  • Rise over a 12 ft run6 ft
  • Rafter length √(rise² + run²)13.4164 ft
  • Angle = atan(rise ÷ run)26.5651°

Rafter length is the sloped distance from wall plate to ridge for this rise and run. It excludes overhang/eave allowance and the ridge-board deduction — add those per your framing plan.

What is the Roof Pitch Calculator?

The ByteTools Roof Pitch Calculator converts between the four ways a roof slope is expressed: the carpenter's x:12 pitch (rise per 12 units of run), the angle in degrees, the slope as a percentage, and a raw rise-over-run measurement.

  • Converts between x:12 pitch, degrees, percent and rise/run
  • Rafter length via the Pythagorean theorem
  • Feet, inches, metres or centimetres
  • Shows the derived rise for your run
  • Flags impossible angles (90° and above)
  • 100% private — works offline on site

How to use the Roof Pitch Calculator

  1. 1

    Choose what you know: rise & run, pitch (x:12), angle in degrees, or slope percent.

  2. 2

    Pick the length unit for the rise, run and rafter.

  3. 3

    Enter your value, plus the horizontal run of the roof.

  4. 4

    Read the pitch, angle, slope percentage and rafter length.

  5. 5

    Click Copy to grab all the results.

About the Roof Pitch Calculator

The ByteTools Roof Pitch Calculator converts between the four ways a roof slope is expressed: the carpenter's x:12 pitch (rise per 12 units of run), the angle in degrees, the slope as a percentage, and a raw rise-over-run measurement. Enter whichever one you know, and the other three are derived instantly using the arctangent relationship.

Give it your horizontal run and it also computes the rafter length from the Pythagorean theorem — the sloped distance from wall plate to ridge. A 6:12 pitch over a 12 ft run, for example, works out to a 26.57° angle, a 50% slope and a 13.42 ft rafter. Results are estimates for planning: they exclude overhangs and ridge deductions, so confirm final cuts against your framing plan and local building code.

The maths runs entirely in your browser — nothing is uploaded, so it is private, instant and works offline on site.

Frequently asked questions

What does a 6:12 roof pitch mean?

It means the roof rises 6 inches for every 12 inches of horizontal run. That equals a 26.57° angle or a 50% slope. The x:12 convention is standard in US carpentry because rafters are laid out with a framing square marked in twelfths.

How do you convert roof pitch to degrees?

Divide the rise by the run, then take the arctangent: angle = atan(rise ÷ run). For a 6:12 pitch that is atan(6 ÷ 12) = atan(0.5) ≈ 26.57°. The calculator does this both ways, so you can start from degrees and get the pitch back.

How is rafter length calculated?

From the Pythagorean theorem: rafter = √(rise² + run²). With a 12 ft run and 6 ft rise the rafter is √(144 + 36) ≈ 13.42 ft. Remember this is the plate-to-ridge line only — add the eave overhang and subtract half the ridge board thickness when cutting.

What is a good pitch for a roof?

Most residential roofs fall between 4:12 and 9:12. Shallower than about 3:12 usually requires membrane or metal roofing rather than shingles, while pitches above 9:12 shed snow well but are harder and more dangerous to work on. Always check the roofing manufacturer's minimum-slope rating and your local building code.

Is roof slope percent the same as degrees?

No. Slope percent is rise divided by run times 100, so a 45° roof is a 100% slope, not 45%. A 50% slope is only about 26.57°. The calculator shows both so the two scales never get mixed up.

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