Grade percent is rise ÷ run × 100
Drainage plans speak in grade percent: a 2% grade drops 2 feet per 100 feet of run — the standard slope for yard drainage away from a foundation. The calculator converts any rise and run into percent, degrees and the ratio form (1:N) that site plans draw.
Where grade matters at home
Soil should fall 6 inches over the first 10 feet from a foundation (5%); sidewalks and patios slope 1–2%; accessible ramps max at 8.33% (1:12). Enter any two of rise, run or percent and the math checks whether your yard, drive or ramp meets the target.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- USDA Natural Resources Conservation Service — soil texture, bulk density and seeding rate guidance.
- US Geological Survey — mineral commodity data and aggregate density references.
- National Stone, Sand & Gravel Association — aggregate grading and product specification references.
Figures, formulas and reference tables last verified: 19 September 2026.