How Is Roof Pitch Measured?

Roof pitch is measured as the number of inches a roof rises vertically for every 12 inches it runs horizontally, expressed as a ratio like 5:12. It's typically measured using a level and tape measure in the attic along a rafter, or with a digital pitch gauge or app on the roof surface itself.

The rise over run method

This is the standard method. Place a level horizontally so it's perfectly flat, measure out exactly 12 inches along it, then measure the vertical distance from that 12 inch mark down (or up) to the roof surface or rafter. Whatever that vertical number is, that's your pitch, written as that number over 12.

Measuring from inside the attic

This is often the easiest and safest approach for homeowners since it avoids getting on the roof itself. You measure along an exposed rafter using the same rise over run method described above.

Measuring on the roof surface

Professionals sometimes measure directly on the roof using a digital pitch gauge or angle finder, especially when attic access is limited or the roof structure is complex with multiple pitches.

Why professionals still do it during inspections

Accurate pitch matters for material compatibility, code requirements and cost estimating, so it's not something to eyeball when it's time to make a decision. It's also common for a single roof to have more than one pitch across different sections, which a full inspection accounts for.