Enter the total organic matter (lbs-BOD5/gal), the design flow (gal/day), and the area (ft^2) into the Organic Loading Rate Calculator. The calculator will evaluate the Organic Loading Rate. 

Organic Loading Rate Formula

The following formula is used to calculate the Organic Loading Rate. 



  • OLR is the Organic Loading Rate (lbs-BOD5/ft^2/day)
  • OM is the total organic matter (lbs-BOD5/gal) 
  • DF is the design flow (gal/day) 
  • A is the area (ft^2) 

To calculate the organic loading rate, multiply the organic matter by the design flow, then divide by the area.

How to Calculate Organic Loading Rate?

The following steps outline how to calculate the Organic Loading Rate.

  1. First, determine the total organic matter (lbs-BOD5/gal).
  2. Next, determine the design flow (gal/day). 
  3. Next, determine the area (ft^2). 
  4. Next, gather the formula from above = OLR = OM*DF/A.
  5. Finally, calculate the Organic Loading Rate.
  6. After inserting the variables and calculating the result, check your answer with the calculator above. 

Example Problem:

Use the following variables as an example problem to test your knowledge.

total organic matter (lbs-BOD5/gal) = 500

design flow (gal/day) = 3000

area (ft^2) = 20

OLR = OM*DF/A =  ?