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FIELD TOOL / 014

Pitch · Degrees · Percent · Geometry

Transparent formula
Roof geometry · Roofing

Roof Pitch Calculator

CALC / 014

Convert measured rise and run, X:12, degrees or percent into one roof slope. Add an optional horizontal run for geometric roof-plane length.

Transparent formulaGeometry only
01 / Slope measurement

Describe your roof slope

Measure vertical rise and horizontal run using matching units. Rise may be zero; run must be positive. Each method keeps its own draft; a blank method does not inherit the other method's result.

Starting 6 in rise / 12 in run is a hypothetical arithmetic example, not a recommended roof pitch. Other methods and project run start blank. Numeric ratio ≤ 1,000,000 and length ≤ 1,000,000,000 m are software guards, not construction limits.

Optional / Project geometry

Enter the horizontal run from low point/eave reference to high point/ridge reference for this roof plane. This is separate from the measurement sample. No building span is halved and no centered gable is assumed. It changes geometric rise/length, never pitch.

No black boxes

One slope.
Visible geometry.

01
Selected input methodratio = Rise ÷ Horizontal run

Rise/Run: divide matching length units. X:12: divide rise per 12 by 12. Angle: tan(degrees × π ÷ 180). Percent: divide by 100.

6 ÷ 12 = 0.5 canonical rise/run ratio. Each method keeps its own draft; raw values are never reinterpreted on a switch.

Zero rise is valid; horizontal run must be positive. Angle must be at least zero and less than 90°.

02
Equivalent representationsPitch X = ratio × 12Angle = atan(ratio) × 180 ÷ πPercent = ratio × 100Factor = √(1 + ratio²)

Ratio 0.5 → X 6, angle 26.5651°, percent 50.0000%, factor 1.118034.

Every output comes from the full-precision canonical ratio, not a rounded displayed pitch. Percent slope and degrees are different representations.

03
Optional project horizontal runProject rise = run × ratioGeometric length = run × factorEquivalent: √(run² + rise²)

Enter the horizontal low-to-high run for the plane being modeled. Project run stays separate from the Rise & Run measurement sample.

Project geometry never changes pitch. No automatic half-span, centered gable, overhang, cut layout or structural sizing is assumed.

Keep measuring

Running length is a separate measurement.

Sum measured runs with Linear Feet. Rafter cut planning and structural sizing remain separate future intents.

01Linear Feet Calculator
01
Geometry field notes

What is roof pitch?

Roof pitch is commonly expressed as vertical rise per 12 units of horizontal run. 6:12 means six units of rise for twelve units of horizontal run. The underlying ratio is dimensionless; matching physical units other than inches can describe the same slope.

02
Geometry field notes

Use the Roof Pitch Calculator

Choose measured Rise & Run, X:12 Pitch, Angle or Percent Slope. Each method retains its own draft. The starting 6 in / 12 in values are a hypothetical arithmetic example; other methods and the optional project run start blank. No roof pitch is recommended.

03
Geometry field notes

Measured rise and horizontal run

Measure vertical rise and horizontal run, not distance along the sloping plane. Divide rise by run in matching units. Rise can be zero; run must be positive. Imperial inches and Metric centimeters convert physically, preserving the same ratio.

04
Geometry field notes

Convert pitch to degrees

Divide X by 12, then use the arctangent of that ratio to find degrees. Keep the normalized X:12 notation; 6:12 is not reduced to 1:2 as the primary roof pitch. Decimal X values such as 4.5:12 remain valid.

05
Geometry field notes

Convert degrees to roof pitch

Take the tangent of the entered angle in degrees, then multiply that ratio by 12. Zero degrees is valid and slopes above 45° are allowed. An angle of 90° does not describe a finite pitch ratio in this model. Extreme values also face a documented software guard, not a design limit.

06
Geometry field notes

Percent roof slope is not degrees

Percent slope is rise ÷ horizontal run × 100. A ratio of 0.5 gives 50% slope and about 26.565°, not 50°. Values above 100% represent slopes steeper than 45° and are mathematically valid within the software guard.

07
Geometry field notes

Understand slope factor

Slope factor is geometric roof-plane length ÷ horizontal run, equal to √(1 + ratio²). At zero slope it is one. It describes this right-triangle geometry; alone it does not calculate roof area, material waste or a finished rafter cut length.

08
Geometry field notes

Optional roof-plane geometry

Enter a separate project horizontal run in feet or meters. Multiply it by ratio for vertical rise and by slope factor for geometric roof-plane length. This run goes from the low-point/eave reference to the high-point/ridge reference of the plane being modeled. No full building span is automatically divided by two and no centered symmetric gable is assumed.

09
Geometry field notes

Roof Pitch and Rafter are separate intents

Geometric roof-plane length does not include overhang, ridge thickness, birdsmouth, plumb cuts, seat cuts, heel height, fascia details or structural sizing. Future Rafter tools remain separate. This page does not design trusses, calculate roof area or roofing quantities, evaluate snow/wind loads or determine code compliance.

10
Hypothetical arithmetic only

Worked geometry examples

Rise/Run: 6 in ÷ 12 in = 0.5. Pitch = 6:12; angle ≈ 26.565°; percent = 50%; factor ≈ 1.1180. These are sample measurements, not a roof recommendation.

Angle: tan(30°) ≈ 0.577350. Pitch ≈ 6.928:12; percent ≈ 57.735%. Outputs use the full ratio, not a rounded 6.93 pitch.

Project: at 6:12 and an entered 10 ft horizontal run, vertical rise is 5 ft and geometric roof-plane length is ≈ 11.18 ft. This is geometric roof-plane length only, not a finished rafter cut length.

Geometry calculator only. Verify roof-system, manufacturer and local-code requirements separately. No pitch, material compatibility or drainage recommendation is provided.

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Common questions

Roof Pitch calculator FAQ

What does 6:12 roof pitch mean?

Six units of vertical rise for twelve units of horizontal run. Its slope ratio is 0.5; it is an arithmetic example, not a recommended roof specification.

How do I calculate roof pitch from rise and run?

Divide vertical rise by positive horizontal run in the same units, then multiply by twelve for the normalized X:12 rise. Zero rise is mathematically valid.

How do I convert roof pitch to degrees?

Divide X by twelve and take atan(ratio), expressed in degrees. Every representation uses the unrounded ratio.

How do I convert degrees to X:12 pitch?

Take tan(angle in degrees) and multiply the ratio by twelve. The input angle must be nonnegative and less than 90°, within the finite software guard.

Is percent slope the same as degrees?

No. Percent is ratio times one hundred, while degrees come from atan(ratio). For example, 50% slope is approximately 26.565°, not 50°.

What is roof slope factor?

The geometric slope-length to horizontal-run ratio: √(1 + ratio²). A ratio of 0.5 gives about 1.1180. It is not automatically a roof-area or material takeoff.

Can the calculator determine roof-plane length?

Yes, with an explicit project horizontal run and valid slope. The result is geometric roof-plane length; project run never changes pitch.

Is roof-plane length the same as rafter length?

It is not a finished rafter cut length. Overhang, ridge thickness, birdsmouth, plumb/seat cuts, heel height, fascia and structural sizing are excluded.

Does BuiltTally recommend a minimum roof pitch?

No. Geometry calculator only. Verify roof-system, manufacturer and applicable local-code/project requirements separately. A calculated pitch is not a safety, buildability or compliance approval.