Calculators / Hardscape
Slope calculator
Measure how much one end is higher, and how far apart the points are. You'll get the slope every way it's written, and whether it meets code for what you're building.
Updated · How we check our numbers
Your slope
2.5% grade
3 in of rise over 10 ft is 1.4°, 1:40, or 0.3 in per foot. As a roof pitch, that's 0.3 in 12.
- Grade
- 2.5%
- Angle
- 1.4°
- Ratio
- 1:40
- Per foot
- 0.3 in
Estimate for planning only, not professional advice. Check the manufacturer’s instructions, your local code and a licensed professional before you buy, build or install. Use at your own risk. Terms.
run = 10 ft × 12 = 120 in
grade = 3 ÷ 120 × 100 = 2.5%
angle = arctan(3 ÷ 120) = 1.4°
pitch = 3 ÷ 120 × 12 = 0.3 in 12
What it meets
model codes- Wheelchair rampno steeper than 1:12 (8.3%), ADA 405.2Meets it
- Soil away from the houseat least 6 in over the first 10 ft (5%), IRC R401.3Too flat
- Patio or walk next to the houseat least 2% away from the house, IRC R401.3Meets it
- Drain pipe, 2½ in or smallerat least ¼ in per ft (2.1%), IPC 704.1Meets it
- Drain pipe, 3 to 6 inat least ⅛ in per ft (1%), IPC 704.1Meets it
- Asphalt shingle roofat least 2 in 12 (16.7%), IRC R905.2.2Too flat
Run a string level (or a straight board and a level) from the high point, measure down to the low point for the rise, and along the string for the run.
These are the model codes. Your town may adopt a different edition or add its own limits, like a steepest driveway grade.
How we work it out
Slope is rise divided by run. Everything else is that number written another way.
grade % = rise ÷ run × 100
angle = arctan(rise ÷ run)
pitch = rise ÷ run × 12, written as "x in 12"
Measure both in the same unit. The run is the level distance, not the length along the slope. Then we check it against the model codes: 6 in of fall over the first 10 ft from a house and 2% on paving next to it (IRC R401.3), a ramp no steeper than 1:12 (ADA 405.2), drain pipe at ¼ or ⅛ in per foot (IPC 704.1) and asphalt shingles at 2 in 12 or steeper (IRC R905.2.2).
Where the numbers come from
Guides
Built on a slope
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