Drainage Calculator by Acreage

Our drainage calculator was developed in partnership with the University of Minnesota Extension to assist you in the preliminary design and understanding of your drainage needs. We encourage you to contact your local design professional or contractor for more specific design guidance and criteria.

These calculations are based on the Manning’s Roughness ASAE EP 260.3 Plastic Tubing Drainage Chart and should be used for estimating purposes only. Consult a Water Table Management Professional for design criteria information.

? = Definition

Enter the Acres to be drained:
Enter the Grade (%): ?

(see below)

Acres Drained
Drainage Coefficient (in: /24 hours) ?
  1/8" 1/4" 3/8" 1/2" 3/4" 1"
Q, flow (cu ft/sec) ?
  Single Wall
Velocity (ft/sec) ?
Calculated Pipe Size (Inches) ?
Actual Pipe Size
Velocity (ft/sec) ?
Calculated Pipe Size (Inches) ?
Dual-wall Mains

Calculate by Pipe Size

Additional Information

NRCS Engineering Field Manual (Chapter 14) suggests the following general range of drainage coefficients:

  Drainage Coefficient (inches to be removed in 24 hours)
Soil Type Field Crops Truck Crops
Mineral 3/8″ to 1/2″ 1/2″ to 3/4″
Organic 1/2″ to 3/4″ 3/4″ to 1-1/2″

(The Minnesota Drainage Guide suggests the lower end of the range.)

Your local NRCS office or state extension service can provide specific recommendations for the soils and crops in your particular area.