Slope calculator

Calculate grades and verify ADA ramp compliance

Try it now

Live calculator

Live preview

Loading calculator...

The Slope Calculator converts between slope expressions (percentage, ratio, degrees) and verifies compliance with ADA accessibility requirements for ramps and walking surfaces.

Understanding slope is essential for accessible design, drainage planning, and grading work. This calculator instantly converts any slope input to all common formats and flags potential code violations.

Enter slope as rise over run, percentage, or degrees, and see equivalent values in all formats. The tool highlights ADA limits for ramps (1:12 max), cross slopes (1:48 max), and walking surfaces.

Features

Everything you need

Convert between %, ratio, and degrees
ADA ramp compliance checking
Cross slope verification
Drainage grade recommendations
Rise/run calculations
Parking lot grade guidelines
Bidirectional conversions

How it works

Simple workflow

1
Enter slope in any format (%, ratio, or degrees)
2
View equivalent values in all formats
3
Check ADA compliance indicators
4
Calculate rise or run for given distances
5
Review grade recommendations by application

Use cases

Built for real-world scenarios

ADA ramp design

Verify ramp slopes meet 1:12 maximum and calculate required ramp length for elevation changes.

Site grading

Convert surveyor grades to percentages and verify drainage away from buildings.

Parking lot design

Check that parking surface slopes meet both drainage and accessibility requirements.

Accessible routes

Verify walkway grades and cross slopes comply with ADA standards.

FAQ

Frequently asked questions

The maximum ADA ramp slope is 1:12 (8.33% or about 4.8 degrees). This means 1 inch of rise for every 12 inches of horizontal run. Slopes up to 1:10 are allowed for existing buildings with space constraints.

Divide 100 by the percentage. For example, 8.33% = 100/8.33 = 1:12. Conversely, divide 100 by the ratio denominator: 1:12 = 100/12 = 8.33%.

ADA limits cross slope to 1:48 (2.08%) maximum for accessible routes. This ensures wheelchairs don't drift sideways. Parking access aisles have the same 2% maximum cross slope.

Minimum drainage slope is typically 1-2% (1/8" to 1/4" per foot). Surface drainage should slope away from buildings at minimum 5% for the first 10 feet. Flat roofs need minimum 1/4" per foot slope.

Have a suggestion?

We're always looking to improve our calculators. If you have ideas for new features, improvements, or found something that could work better, we'd love to hear from you.

Related tools