Grade describes how steep a driveway, path, road, ramp or drain is. Driveways should usually stay below 12–15%, accessible walks below 5%, and drains and gutters need at least 1–2% fall. Surveyors and civil plans express grade as a percentage; landscapers often use a ratio like 1:20.
How to use the Elevation Grade Calculator
- Elevation change
- Horizontal distance
- Every result field is editable: type into Grade and Elevation change plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the elevation change (rise or fall) and the horizontal distance. Type a grade into the result to find the elevation change it needs.
Tips for an accurate estimate
- Measure angles with a digital angle finder or sliding bevel, not by eye.
- Make a test cut in scrap before cutting expensive stock.
- Small angle errors add up over many joints – check the first assembly before cutting the rest.
- Keep a written list of the dimensions and angles you set on the saw or machine.
Common mistakes to avoid
- Reading the saw scale as the angle from the edge rather than from square.
- Rounding intermediate results too early.
- Mixing degrees and percent grade.
Inputs explained
| Field | What to enter |
|---|---|
| Elevation change | Units: ft, m, in, yd, cm |
| Horizontal distance | Units: ft, m, in, yd, cm |
What each result means
- Grade = [Elevation change]÷[Horizontal distance]×100
- Angle = deg(atan([Elevation change]÷[Horizontal distance]))
- Ratio 1 : = [Horizontal distance]÷[Elevation change]
- Fall per foot = [Elevation change]÷[Horizontal distance]×12
- Slope length = sqrt([Elevation change]^2 + [Horizontal distance]^2)
Example values
How the main result changes when Elevation change changes and everything else stays at the example values above:
| Elevation change (ft) | Grade (%) |
|---|---|
| 1 | 2 |
| 1.5 | 3 |
| 2 | 4 |
| 2.5 | 5 |
| 3 | 6 |
| 4 | 8 |
Formula
Grade = rise ÷ run × 100%Angle = atan(rise ÷ run)Ratio = 1 : run ÷ rise; slope length = √(rise² + run²)Worked example
Inputs — Elevation change: 2 ft; Horizontal distance: 50 ft.
Results — Grade = 4 %; Angle = 2.291 °; Ratio 1 : = 25; Fall per foot = 0.48 in/ft; Slope length = 50.04 ft.
Frequently asked questions
What is a 2% grade?
A fall of 2 ft over 100 ft, or about ¼ in per foot – a common minimum for drainage.
How steep can a driveway be?
Up to about 12–15% for most cars; steeper drives need special design for traction and scraping.
Is grade the same as angle?
No: 100% grade is 45°; 10% grade is 5.7°.
What formula does the Elevation Grade Calculator use?
Grade = rise ÷ run × 100%.