Driveway Slope Calculator
Calculate driveway slope as a percent grade and in degrees from rise and run, to check it against typical drainage and vehicle-clearance limits.
How this calculator works
Driveway slope compares how much a surface rises over a given horizontal distance. This calculator takes the rise and run you enter and converts that ratio into two familiar numbers: a percent grade, which is what most drainage and driveway codes reference, and an angle in degrees, which is easier to picture as steepness.
Both numbers come from the same rise-and-run inputs, just expressed differently. Percent grade is a straight ratio, while the angle uses the arctangent function to convert that ratio into degrees from level ground.
Formula: Slope percent = (rise in feet ÷ run in feet) × 100. Angle = arctangent(rise ÷ run).
Worked example
A driveway rises 6 inches over a 20 ft run:
- Rise: 6 in = 0.5 ft
- Run: 20 ft
- Slope percent: 0.5 ÷ 20 × 100 = 2.5%
- Angle: arctangent(0.5 ÷ 20) ≈ 1.43°
Notes
Most local codes want driveway slope under roughly 15-20% for everyday passenger vehicles to keep them from bottoming out or losing traction. A slope over roughly 4-5% typically needs a transition, or apron, where the driveway meets the street, so the change in angle doesn’t scrape the underside of the car.
A slope near 1-2% is generally considered ideal for drainage — enough to carry rainwater away from the house or garage without making the driveway feel steep to walk or park on. Slopes outside these ranges aren’t automatically a problem, but they’re more likely to trigger a closer look from an inspector or require extra grading work.
How to use
Enter the rise (the vertical height difference) and the run (the horizontal distance it occurs over), in the same units. The calculator returns the slope as both a percent grade and an angle in degrees, which you can then compare against the general ranges above or your local code.
This is a planning estimate. Local codes set exact maximum driveway slope and apron transitions — confirm with your municipality before grading.
Frequently asked questions
What is the difference between slope percent and degrees?
Slope percent compares rise to run directly — a 2.5% slope means the surface climbs 2.5 ft for every 100 ft traveled. Degrees measure the actual angle from level ground, found with the arctangent of rise over run. Percent grade is what most codes and drainage specs reference, while degrees are more familiar for visualizing steepness.
How do I measure rise and run on an existing driveway?
Run is the horizontal distance from the street to the point you're checking, measured in feet. Rise is the vertical height difference between the two ends over that same distance, which you can find with a level and tape measure or a laser level. Keep both measurements in the same units before dividing.
Why does a steep slope need a transition apron?
Where a driveway meets the street, a sudden change in angle can drag the lowest part of a vehicle — bumper, exhaust, or undercarriage — against the pavement. A transition apron eases that angle change gradually instead of all at once. Steeper driveways need a longer or more gradual apron to avoid scraping.
Is a flatter driveway always better?
Not quite — a driveway that's too flat can pool water instead of draining it toward the street. A small amount of slope is what carries rainwater away from the garage or house. The goal is enough grade for drainage without exceeding what vehicles and local code can handle.
Estimates only. Verify quantities with your supplier before purchasing.