Calculators / Pounds Formula
Pounds Formula calculator
The pounds formula turns a flow and a concentration into a load in pounds per day. You will use it on BOD loading, solids wasting, chlorine feed and most other loading questions on the Class I and II exams.
lbs/day = Flow (MGD) × Concentration (mg/L) × 8.34 lbs/gal
Worked example
A plant receives 2.5 MGD with an influent BOD of 200 mg/L. How many pounds of BOD per day enter the plant?
- 2.5 MGD × 200 mg/L × 8.34 = 4,170 lbs/day
Answer: 4,170 lbs/day
Common mistakes
- Using gpd instead of MGD. Divide gpd by 1,000,000 first.
- Dropping the 8.34. It converts million gallons of water to million pounds.
Check your exam's reference sheet for its exact constants. Some use 3.14 instead of 3.1416, which changes answers in the last digit.