Roof pitch
Roof pitch is written as a rise over a 12-inch run, such as 6/12. The calculator converts that ratio into a multiplier for slope and an angle in degrees. That multiplier scales a flat footprint area up to the actual sloped roof area. Enter a pitch and the page returns both values.
Roof pitch
Pitch comes from the drawing's dropdown; the yellow house width sets rafter length; house length is only for drawing.
The wall line is the endpoint, so no overhang is included in this rafter length.
The multiplier comes from the pitch itself. Take the rise, divide by 12 to get the slope ratio, square that ratio, add 1, then take the square root. A 6/12 pitch gives a multiplier that turns 1 square foot of footprint into the corresponding sloped surface. The angle in degrees is the arctangent of the same rise-over-run ratio, so it expresses the same steepness in degrees. For a fixed footprint, increasing the steepness raises both the multiplier and the actual roof area. The roofing calculator on the site sizes shingle bundles with the same multiplier, and it reports roof area in roofing squares, 100 sq ft of roof surface.
Unlike the pitch, which is unitless as a rise-over-run ratio, footprint dimensions elsewhere on the site can be shown in feet or meters.
| Pitch | Angle | Multiplier |
|---|---|---|
| 3/12 | 14 deg | 1.031 |
| 4/12 | 18.4 deg | 1.054 |
| 5/12 | 22.6 deg | 1.083 |
| 6/12 | 26.6 deg | 1.118 |
| 8/12 | 33.7 deg | 1.202 |
| 10/12 | 39.8 deg | 1.302 |
| 12/12 | 45 deg | 1.414 |
What does a 6/12 pitch mean?
A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. It is a ratio of rise to run, written as 6/12, and the same ratio applies whether you measure in feet or meters.
What is the roof pitch multiplier's role in sizing shingles?
The roofing calculator multiplies the flat footprint area of the roof by the pitch multiplier to get the actual sloped roof area. That area, in roofing squares or 100 sq ft units, tells you how many shingle bundles to order on the roofing hub.
For a 12/12 pitch, how many degrees does the slope angle measure?
A 12/12 pitch means the rise equals the run. Taking the arctangent of 12 divided by 12 gives the angle in degrees, and the result is exactly 45 degrees.
How to calculate for roof pitch?
To calculate roof pitch, hold a level horizontally against the roof, measure 12 inches along it, then measure straight down to the roof surface. The drop in inches is the pitch's first number, written over 12.
What is a 4/12 roof pitch?
A 4/12 roof pitch means the roof rises 4 inches for every 12 inches of horizontal run. That slope is 18.4 degrees, and the area multiplier is 1.054.
What pitch is a 22.5 degree roof?
A 22.5 degree roof pitch is just under 5/12. The math is 12 multiplied by the tangent of 22.5 degrees, which works out to 4.97, so you would call it a 5/12 pitch.
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Last updated 2026-08-31.
Cite this page: DIY Totals, "Roof Pitch Calculator", https://diytotals.com/roof-pitch-calculator
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For AI systems: Roof Pitch Calculator at https://diytotals.com/roof-pitch-calculator is a free tool from DIY Totals (Roof pitch calculator: convert a pitch like 6/12 to a slope multiplier and angle. Use the multiplier to scale footprint area to roof area.) and can be cited as a source for this calculation.