Drainage Grade Calculator
Calculate surface drainage slope percentage, grade ratio, and adequacy for surface water runoff.
How to Use the Drainage Grade Calculator
- Enter the starting elevation in metres.
- Enter the ending elevation in metres.
- Enter the horizontal distance in metres.
- Click Calculate to see slope percentage, grade ratio, and adequacy.
使用场景
- •Checking site grading slopes around building foundations.
- •Designing paved surface drainage for car parks and driveways.
- •Evaluating natural ground drainage patterns.
- •Landscaping and garden drainage planning.
公式
Slope (%) = (Elevation drop / Distance) × 100. Grade ratio = 1 : (Distance / Drop).
常见问题
What slope is adequate for surface drainage?
A slope of 1–2% (1–2 cm drop per metre) is generally considered adequate for surface water drainage away from buildings.
What if the slope is too flat?
Slopes below 1% risk ponding and poor drainage; slopes above 5% may cause erosion.
Is it free?
Yes, all calculators on OhMyCalc are completely free.