Roof Pitch Calculator
Convert roof pitch between ratio, degrees, and percentage. Calculate the pitch multiplier for material estimation, determine rafter length, and find the actual roof surface area from your building footprint dimensions.
Pitch Measurements
Common Roof Pitches
Pitch Analysis
Derived Roof Values
How to Calculate Roof Pitch
Roof pitch describes the steepness of a roof and can be expressed three ways: as a ratio (rise:run), as an angle in degrees, or as a percentage slope.
Pitch Ratio to Degrees
Pitch Ratio to Percentage
Pitch Multiplier (for material estimation)
Common Pitch Multipliers
Use this table to quickly find the pitch multiplier for common roof pitches. Multiply your building footprint by the multiplier to get the actual roof surface area.
| Pitch | Angle | Multiplier | Slope % | Category |
|---|---|---|---|---|
| 2:12 | 9.46° | 1.014 | 16.7% | Low Slope |
| 4:12 | 18.43° | 1.054 | 33.3% | Conventional |
| 6:12 | 26.57° | 1.118 | 50.0% | Conventional |
| 8:12 | 33.69° | 1.202 | 66.7% | Steep |
| 10:12 | 39.81° | 1.302 | 83.3% | Steep |
| 12:12 | 45.00° | 1.414 | 100.0% | Very Steep |
Example Pitch Calculation
Calculating roof area for a 6:12 pitch, 40′ × 30′ building
- Step 1: Rise = 6 in per 12 in run → Ratio = 6/12 = 0.5
- Step 2: Pitch angle = arctan(0.5) × (180/π) = 26.57°
- Step 3: Pitch multiplier = √(1 + 0.5²) = 1.118
- Step 4: Building footprint = 40 × 30 = 1,200 sq ft
- Step 5: Actual roof area = 1,200 × 1.118 = 1,342 sq ft
- Step 6: Slope percentage = 0.5 × 100 = 50%
Common Mistakes in Roof Pitch Measurement
Measuring pitch from the attic ceiling
Pitch is measured from the roof sheathing, not the ceiling joists. Ceiling joists may have additional framing that changes the effective slope. Always measure directly on the rafters.
Confusing pitch with slope percentage
A 6:12 pitch equals a 50% slope, not 6%. The pitch ratio is rise over 12 inches of run; the percentage is rise divided by run times 100. Mixing these up leads to ordering the wrong materials.
Using the wrong multiplier for complex roofs
The pitch multiplier only works for simple gable roofs. Hip roofs, gambrels, and roofs with dormers have more complex geometry. Measure each roof plane separately and sum the areas.
Frequently Asked Questions
What is roof pitch?
Roof pitch is the steepness of a roof, expressed as a ratio of vertical rise to horizontal run. For example, a 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. Pitch can also be expressed in degrees or as a percentage.
How do you convert roof pitch to degrees?
To convert roof pitch to degrees, use the arctangent function: degrees = arctan(rise / run) x (180 / pi). For a 6:12 pitch, arctan(6/12) = 0.4636 radians, which equals 26.57 degrees.
What is a roof pitch multiplier?
The roof pitch multiplier (or correction factor) converts a flat building footprint into the actual sloped roof area. It is calculated as the square root of (1 + (rise/run) squared). A 6:12 pitch has a multiplier of 1.118, meaning the roof surface is 11.8% larger than the footprint.