How to use it
There are four boxes for the same slope. Type in any one and the other three show the conversion. To find how much a surface rises or falls over a distance, put that distance in Over a run.
- In per ft is inches of rise for each foot of run:
1/4,0.25or1/4". Written as6/12it is read as a roof pitch, six inches per foot. - Percent is rise ÷ run × 100:
2or2%. - Degrees is the angle from level:
1.2. - Ratio is rise to run:
1:48, or just48for one in forty-eight.
Worked example
A quarter inch per foot is 2.083%, 1.193° and 1:48. Over a 20' run it falls 5".
The math
- Percent = inches per foot ÷ 12 × 100.
- Ratio = 1 : (12 ÷ inches per foot).
- Degrees = arctangent of rise ÷ run. Percent and degrees are not the same thing: a 100% grade is 45°, not 90°.
- Rise = run × slope.
Common slopes
| Inches per foot | Percent | Degrees | Ratio |
|---|---|---|---|
| 1/8" per ft | 1.042% | 0.597° | 1:96 |
| 1/4" per ft | 2.083% | 1.193° | 1:48 |
| 3/8" per ft | 3.125% | 1.79° | 1:32 |
| 1/2" per ft | 4.167% | 2.386° | 1:24 |
| 3/4" per ft | 6.25% | 3.576° | 1:16 |
| 1" per ft | 8.333% | 4.764° | 1:12 |
| 2" per ft | 16.667% | 9.462° | 1:6 |
| 3" per ft | 25% | 14.036° | 1:4 |
| 4" per ft | 33.333% | 18.435° | 1:3 |
| 6" per ft | 50% | 26.565° | 1:2 |
| 12" per ft | 100% | 45° | 1:1 |
Questions
What is 1/4 inch per foot as a percent?
A quarter inch per foot is 2.083%. Divide the inches per foot by 12 and multiply by 100. It is also 1:48 and 1.193°.
How do I convert percent slope to inches per foot?
Multiply the percent by 12 and divide by 100. A 2% slope is 0.24 inches per foot, which is about 1/4" on a tape measure.
How do I convert percent slope to degrees?
Divide the percent by 100 and take the arctangent. A 10% slope is 5.711°, and a 100% slope is 45°.
How much fall is there over a given distance?
Multiply the run by the slope. At 1/4 inch per foot, a 20 foot run falls 5". Put the distance in the Over a run box and the calculator shows it in feet and inches.
Is roof pitch the same as inches per foot?
Yes. A 6/12 roof rises 6 inches for every 12 inches of run, which is 6 inches per foot. For rafter lengths, use the roof pitch calculator.
More calculators
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- Stair calculatorEnter the floor-to-floor rise to get risers, treads, total run and stringer length.
- Circle & arc calculatorEnter a diameter for circumference and area. Add an angle for arc length and chord.
- Square footage & volume calculatorEnter length and width for area. Add a height for volume, cubic yards and wall area.
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- Concrete calculatorPick slab, footing, wall or round column, type the size in feet and inches, and get cubic yards and bags.
- Gravel, sand, soil & mulch calculatorPick the material, type the length, width and depth, and get cubic yards and approximate tons.
- Drawing scale calculatorEnter a scale and a length to convert it, or a drawn length and its real size to find the scale.
Reference finders
- DSA forms & publications finderType a topic or a number, or paste a plan check comment, and see which DSA documents to open.
- OSHPD / HCAI CAN, PIN & forms finderType a topic or a number, or paste a plan review comment, and see which HCAI documents to open.