Rise over run, in every form.
Roofers say 6/12. Racking specs and some manufacturer sheets ask for degrees. The squares math wants a multiplier. Put in the rise and the run and get all of them at once.
Redline keeps the pitch and the photos on the job, so the quote and the crew's job notes start from the same roof.
Try Redline freeHow the math works
Pitch is how many inches the roof climbs for every 12 inches it runs level. Measured over a different run, it scales: 12 inches of rise over a 24 inch level is still 6/12, and so is 4.5 over 9.
The angle is the arctangent of rise over run, turned into degrees. The slope percentage is just rise divided by run. The pitch factor is how long the slope is for each unit of level run: the square root of (rise squared plus run squared), divided by the run. Multiply a flat footprint by it and you have the sloped roof surface, which is what the last line shows per 100 sq ft.
Common pitches
| Pitch | Angle | Slope | Pitch factor | Roof per 100 sq ft of footprint |
|---|---|---|---|---|
| 3/12 | 14.0° | 25% | 1.031 | 103.1 sq ft |
| 4/12 | 18.4° | 33.3% | 1.054 | 105.4 sq ft |
| 5/12 | 22.6° | 41.7% | 1.083 | 108.3 sq ft |
| 6/12 | 26.6° | 50% | 1.118 | 111.8 sq ft |
| 7/12 | 30.3° | 58.3% | 1.158 | 115.8 sq ft |
| 8/12 | 33.7° | 66.7% | 1.202 | 120.2 sq ft |
| 9/12 | 36.9° | 75% | 1.250 | 125.0 sq ft |
| 10/12 | 39.8° | 83.3% | 1.302 | 130.2 sq ft |
| 12/12 | 45.0° | 100% | 1.414 | 141.4 sq ft |
Geometry only. The calculator shows the factor to two places; the table carries three so you can check your own math.
What to watch for
- Keep the level level. A bubble that's a little off at 12 inches turns into a wrong pitch across the whole roof. Measure twice, in two spots.
- Mixed roofs. The main roof, the porch and the dormers often differ. Measure and record each one.
- Geometry, not a rulebook. This tool doesn't say whether a pitch is walkable, which underlayment or shingle it needs, or what your code requires. That's the manufacturer's install instructions and your local code.
- The factor works on the footprint you give it. Add the overhang to the footprint first, or use the roofing squares calculator, which does it for you.
Questions contractors ask
Is 6/12 the same as 6 in 12?
Yes. Both mean 6 inches of rise for every 12 inches of run. You'll also see it written 6:12.
How do I get the pitch from an angle?
Pitch equals the tangent of the angle times 12. A 30 degree roof is about 6.9 in 12, so between a 6 and a 7.
Can I measure it from the attic?
Yes. Hold the level against the underside of a rafter, mark 12 inches along the level, and measure straight up to the rafter. The roof surface has the same pitch as the rafter under it.
Where does the pitch go in Redline?
On the job and in the quote. Snap the level shot into Quick-Sort from the ladder and file it to the job later. Then tell the chat "quote the Parks: 22 squares at 9/12, steep charge on the back, one layer off" and it drafts the lines at your prices for you to check. Quotes work on every plan; invoicing the job later is on Solo.
Where pitch comes up
Keep reading
- Roofing squares calculatorFootprint, overhang and pitch into squares and bundles to order.
- Gutter calculatorEave length and your rules into gutter feet, downspouts, elbows and hangers.
- Roofing estimate appSquares, layers and edge footage in, an itemized roof quote with a deposit out.
- Quick-SortA drop box for the field. Capture now, and Redline suggests where it belongs.