How to use this calculator
Select the conversion mode matching your known measurement. Enter the slope percentage, inches per foot, angle, ratio, rise and run, or elevations. Then choose the horizontal run and its unit. The result updates while typing when automatic calculation is enabled.
Use the direction control to describe upward or downward movement. A fall reduces the ending elevation. A rise increases it. Direction changes the interpretation, but not the magnitude of a positive slope.
Understanding percent slope
Percent slope compares vertical change with horizontal run. A two percent slope means two units of vertical change per one hundred equal horizontal units. It does not mean two degrees. The equivalent angle is calculated using the arctangent function.
Inches per foot expresses the same relationship across twelve horizontal inches. Multiply the decimal grade by twelve. Thus, two percent becomes 0.24 inches per foot.
Decimal and fractional inches
Engineering work often uses decimal measurements. Construction work often uses fractions. Choose the preferred fraction precision. The calculator displays the nearest supported fraction and the rounding difference. Internal calculations retain full precision before display rounding.
Rise over a custom distance
Enter the complete horizontal run to calculate cumulative rise or fall. A two percent slope across twenty-five feet changes elevation by six inches. The station table breaks that run into repeatable field layout intervals.
Elevation calculations
Optional starting elevation produces an ending elevation. The dedicated elevation mode can instead derive percent slope from known start and end elevations. Always use compatible units and a nonzero horizontal distance.
Common mistakes
- Do not treat percent slope as an angle.
- Use horizontal run, not sloped surface length.
- Keep rise and run units consistent.
- Confirm whether the project rises or falls.
- Round only after the full calculation.
Practical applications
This tool supports drainage layouts, patios, driveways, gutters, roofs, landscaping, roads, ramps, sewer lines, deck drainage, and general grading work. Application presets are starting examples only. Project drawings and governing requirements remain authoritative.