Roofing & Exterior calculator

Roof Pitch CalculatorPitch, Slope and Roof Angle

Calculate roof pitch, slope percentage and angle in degrees from vertical rise and horizontal run. Convert measured roof slope into common roofing formats.

Updated August 20, 2026

✓Instant estimateNo sign-up required

✓Clear formulaSee how the result is built

✓Editable inputsMatch your product

✓Practical roundingPlan real purchase units

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Project details

Enter your measurements and material details.

Planning estimate only. Verify product specifications and project requirements before ordering.

💡Tip:

Measure rise and horizontal run, not the length along the rafter.

How the Roof Pitch Calculator works

Roof pitch is the ratio of vertical rise to horizontal run. The calculator normalizes that ratio to 12 inches of run, converts it to percent slope and uses arctangent to find the angle in degrees.

Formula

Pitch on 12 = rise ÷ run × 12. Slope % = rise ÷ run × 100. Angle = arctan(rise ÷ run).

Measure before you buy

Use a level or reliable drawing to determine vertical rise over a known horizontal run. A common field measurement uses 12 inches of horizontal run, but any consistent pair of dimensions works.

Pitch is a ratio and does not directly give roof area.
Complex roofs can have multiple pitches.
Roof work involves fall hazards; measuring from plans or safe locations is preferable.

Common questions

What does a 6:12 roof pitch mean?

The roof rises 6 inches for every 12 inches of horizontal run.

What angle is a 6:12 pitch?

About 26.6 degrees.

Is pitch the same as slope percentage?

They describe the same relationship in different formats.

Can I enter centimeters?

Yes if rise and run use the same unit because the ratio is unitless.

Does this calculate rafter length?

No. It reports pitch, slope and angle.

Worked example: Roof Pitch Calculator

Using the example inputs shown in the calculator — Rise (in) = 6, Run (in) = 12 — the result is 6:12 pitch. This demonstrates the formula with a complete set of numbers rather than a hidden assumption.

The result breakdown also shows Slope: 50%; Angle: 26.57°. Replace the example values with field measurements and the exact product coverage, yield or package size you plan to buy.

Recalculate the roof pitch calculator whenever the measured dimensions or product specification changes. Keep the calculator result separate from any structural or code decision.