Roofing Calculators
Roof Pitch Calculator
Enter your roof's rise and run to calculate pitch ratio, angle in degrees, slope percentage, pitch multiplier, and rafter length. Real-time SVG diagram updates as you type.
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Pitch Diagram
Pitch Ratio
4.00 : 12
rise per 12 units of run
Angle
18.43°
degrees from horizontal
Slope
33.33%
rise ÷ run × 100
Rafter Length
316.23 mm
per unit of run entered
Pitch Multiplier
1.0541
Pitch Category
Low
Area Increase
+5.41%
Calculation Breakdown
Common Australian Roof Pitches
Standard roof pitch values with multipliers and typical applications in Australian construction.
| Pitch | Degrees | Multiplier | Common Use |
|---|
Roof Area Calculator
Calculate true sloped roof area from building dimensions and roof pitch. Results in square feet, square metres, and roofing squares.
Calculate Roof Area →Pitch to Degrees Converter
Quickly convert between pitch ratios, degrees, and slope percentages with our simple conversion tool.
Convert Pitch to Degrees →All Roofing Calculators
Browse our full suite of free roofing calculators for every roof type and measurement need.
View All Calculators →Frequently Asked Questions
Common questions about roof pitch calculation
What is roof pitch?
Roof pitch is the ratio of the vertical rise to the horizontal run of a roof. In Australia, it's commonly expressed as degrees (e.g. 22.5°) or as a ratio like X:12, meaning the roof rises X units for every 12 units of horizontal run.
How do I measure my roof pitch?
Place a spirit level horizontally against a rafter in your attic. Measure 300mm along the level from the rafter, then measure the vertical distance from the end of the level down to the rafter. Divide the vertical distance by 300 to get the rise per unit of run, then enter both values into the calculator.
What is a common roof pitch in Australia?
Most Australian roofs have a pitch between 15° and 25°. The minimum pitch for metal roofing is typically 5° (1:12), while concrete and terracotta tiles require at least 20°. Heritage homes in the Barossa Valley often feature steeper pitches of 30°–45°.
What is a pitch multiplier?
The pitch multiplier (also called the slope factor) converts a flat footprint area to the true sloped roof area. For example, a 6:12 pitch has a multiplier of 1.1180, meaning the sloped area is 11.8% larger than the flat footprint. Multiply your footprint area by this factor to get the actual roof area.
How does roof pitch affect cost?
Steeper roofs cost more because they require more roofing material (larger sloped area), additional safety equipment for installers, and more labour time. A 45° roof has about 41% more surface area than a flat roof of the same footprint, significantly increasing material and installation costs.
What roof pitch do I need for solar panels?
In South Australia (latitude ~35° south), the optimal roof pitch for solar panels is 30°–35° facing north. Panels can still perform well on pitches between 10° and 40°. If your roof pitch differs significantly, tilt frames can be used to adjust the panel angle for maximum energy generation.
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