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Measurement & Conversion

Slope & Grade Calculator

This slope calculator converts rise and run into grade, angle, ratio and inches per foot; see our yard drainage guide for grading tips. Construction uses several ways to express slope: percent grade for driveways and drainage, a ratio like 1:12 for ramps, inches per foot for pipes and patios, and degrees for everything else. Enter a rise and run — or a target grade and a run — and get them all at once.

Results from this slope calculator are planning estimates; confirm quantities and prices with your supplier or contractor before you order.

Enter your project

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Results

Your results will appear here

Enter your measurements and press Calculate. Defaults show a typical example.

How to use the slope calculator

  1. Choose what you want to find.
  2. Enter the horizontal run (and the rise, if finding the slope).
  3. For drainage or a driveway, enter the target grade to see the drop over the run.

Formula

Grade = rise ÷ run; percent = grade × 100; angle = arctan(grade); ratio = 1 : (run ÷ rise); inches per foot = grade × 12.

Worked example

A 1 ft rise over 12 ft is an 8.33% grade, 4.76°, a 1:12 ratio and 1 in per foot. For a patio sloped at 2% over 10 ft, the drop is 0.2 ft — about 2⅜ in.

Tips for using the slope calculator

  • Grade soil away from the house at least 6 in over the first 10 ft where space allows.
  • Accessible ramps are limited to a 1:12 slope; driveways and walks have their own local limits.
  • Use a string line and level to measure rise over a known run on site.
Paving crew in high-visibility vests laying fresh asphalt with a paving machine

Slope Calculator FAQs

How much slope does a patio need?

Patios and walks are commonly sloped about 1–2% (⅛–¼ in per foot) away from the house so water drains. Follow your plans and local requirements.

What is the slope for a wheelchair ramp?

Under the ADA Standards the maximum running slope is 1:12 (8.33%). Local codes may add requirements.

What grade is too steep for a driveway?

Many municipalities cap driveway grades (often in the 10–15% range) and require transitions at the street. Check your local standards.

Estimate before you call a contractor

Run the numbers with our free calculators so you can compare bids with confidence.

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