Quick answer
Roof Pitch Calculator: direct answer
Roof Pitch Calculator helps you convert rise and run into roof pitch, angle, slope percentage, rafter length, and pitch multiplier. It is best for pitch conversion, slope, and roof area planning and returns pitch ratio, roof angle in degrees, slope percentage for material planning.
Use this calculator when you know rise and run, pitch ratio such as 6:12, angle in degrees when converting from angle. The estimate uses this rule: pitch = rise / run x 12; angle = arctan(rise / run).
Inputs
- Rise and run
- Pitch ratio such as 6:12
- Angle in degrees when converting from angle
- Consistent measurement units
Outputs
- Pitch ratio
- Roof angle in degrees
- Slope percentage
- Pitch multiplier
- Rafter length
Formula
How this estimate works
pitch = rise / run x 12; angle = arctan(rise / run)
In plain terms, compare rise to horizontal run, convert that ratio into pitch, degrees, slope percent, and multiplier, then use the result for roof planning.
A roof with 6 in rise over 12 in run is a 6:12 pitch, about 26.57 degrees, with a 1.118 pitch multiplier.
Use cases
When to use this calculator
Turn rise and run into pitch ratio, degrees, slope percentage, and multiplier from one measurement.
Use the pitch multiplier before estimating shingles, underlayment, or sloped roof surface area.
Compare roof details when one source uses 6:12 pitch and another uses angle or slope percentage.
Worked example
Convert a 6 in rise over 12 in run
A 6:12 pitch is a common roof slope. The calculator converts it into degrees, slope percentage, pitch multiplier, and rafter length for quick planning.
- Enter 6 for rise and 12 for run.
- Use the angle when comparing roof slope descriptions across plans or product instructions.
- Use the pitch multiplier with a roof area calculator when estimating surface area from a flat footprint.
Planning reference
Common roof pitch reference
These pitch examples help check whether the calculator result is in the expected range before using the pitch multiplier on a roof area estimate.
How roof pitch is calculated
Roof pitch in the United States is usually expressed as inches of rise for every 12 inches of run. Divide rise by run, then multiply by 12. The same ratio can be converted to degrees with arctangent.
Why pitch multiplier matters
A roof's surface area is larger than its flat footprint. The pitch multiplier estimates the extra surface area caused by slope and is useful when estimating roofing materials.
Measurement tips for a better estimate
- Measure vertical rise and horizontal run, not the sloped rafter length.
- A common field method is to measure rise over a 12 inch horizontal run.
- For complex roofs, check each roof plane because pitch can change from section to section.
Common estimating mistakes
- Measuring along the rafter instead of measuring vertical rise and horizontal run.
- Mixing inches and feet in the same pitch calculation.
- Using roof pitch alone for material quantity without also estimating roof area and waste.
Ordering checks
Check these before using the result
- Use measured rise and horizontal run, not the sloped rafter length.
- Measure each roof plane separately if an addition, porch, dormer, or garage roof has a different pitch.
- After pitch is known, move to roof area or roofing material calculators for quantities.
Assumptions used
- Pitch is shown as inches of rise per 12 inches of horizontal run.
- Rafter length uses the same units entered for rise and run.
- Pitch multiplier estimates sloped surface area from flat footprint area.
Before you order materials
- Measure horizontal run, not the sloped rafter distance.
- Use the multiplier with actual roof footprint measurements.
- Check roofing manufacturer requirements for low-slope roofs.
Frequently asked questions
What does 6:12 pitch mean?
It means the roof rises 6 inches for every 12 inches of horizontal run.
Is pitch the same as degrees?
No. Pitch is a rise-over-run ratio, while degrees describe the angle. This calculator shows both.
Can I use this for material estimates?
Use the pitch multiplier as a planning estimate, then confirm roof area and waste before ordering materials.
How does pitch affect roof area?
Steeper pitch increases roof surface area. Convert pitch into a multiplier, apply it to the flat footprint, then add waste for cuts and layout.