Grading & Drainage Calculators
Getting water to move away from a house is the whole job, and it comes down to two things: shape the ground so it slopes away, and drain whatever the slope can't shed. These are the calculators LevelCalc is named for — leveling, grading, and drainage — from setting the slope at the foundation to ordering the dirt, gravel, pipe, and wall block to do it.
The single rule that matters most: the ground must fall at least 6 inches in the first 10 feet away from the foundation (a 5% slope, per IRC R401.3). Too little fall is the most common cause of wet basements and foundation damage.
Start here: the all-in-one planner
Describe the problem once and the planner returns the slope you need, the fill dirt to order, and a sized French drain with gravel, pipe, and a cost range — instead of stitching three separate calculators together.
All Grading & Drainage Tools
How a Grading & Drainage Project Comes Together
- Set the slope. Establish at least 6" of fall over the first 10 ft at the foundation, then ~2% across the rest of the yard. Use the Slope Calculator to convert between percent, ratio, and inches per foot.
- Move the dirt. Build the new grade as a wedge of fill and figure the volume — including compaction — with the Fill Dirt & Excavation Calculator and Topsoil Calculator.
- Drain the rest. Where slope alone won't clear the water, size a French drain and its outlet pipe.
- Hold the grade. On a slope change, a retaining wall keeps the new grade in place, and pavers or a gravel driveway finish the surface.
Slope Reference
- At the foundation: 6" fall in the first 10 ft (5%) — IRC R401.3 minimum
- Across a lawn: 2% minimum (1/4" per foot) for positive drainage
- Hard surfaces (patios, drives): 1–2% away from the house
- French drain pipe: at least 1% (1/8" per foot) toward the outlet
- Maximum mowable turf: about 3:1 (33%) before terracing or walls
Disclaimer
These calculators provide estimates only. Actual quantities, slopes, and costs vary with site conditions, soil, compaction, access, and local code. Always verify the grade at the foundation with a level and confirm requirements with your building department before starting work. See our Terms of Use.