Slope and Grade Calculator
Convert a rise and run into slope percentage, ratio, angle and the required pipe fall.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Slope is rise divided by horizontal run. This calculator converts the measurement to percent, angle, vertical-to-horizontal ratio and inches of fall per foot. It does not determine whether a surface is safe, drains correctly or meets accessibility or building requirements.
Worked example
calculated with the default values below
Rise 2 in · Run 10 ft Slope 1.67 % · Angle 0.95 ° · Slope ratio 1:60.0 (vertical:horizontal) · Fall per foot 0.200 in/ft
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
G = R÷(12r)×100; θ = atan2(R, 12r)×180÷π; q = R÷r; ratio = 1:(100÷G)
- R
- Rise (in)
- r
- Horizontal run (ft)
- G
- Slope grade (%)
- θ
- Slope angle (°)
- q
- Rise per foot (in/ft)
- ratio
- Slope ratio (vertical:horizontal)
Slope (%) = rise ÷ horizontal run × 100; angle = arctan(rise/run). This is geometric conversion only, not a safety or code-compliance assessment.
Frequently asked questions
Does this calculator check accessibility compliance?
No. It converts slope measurements only. Accessibility requirements can include limits for running and cross slope, landings, width, rise and surfaces. Check the applicable standards and consult a qualified professional. See the [U.S. Access Board](https://www.access-board.gov/ada/).