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Pounds Formula Calculator
The pounds formula (lbs/day = mg/L x MGD x 8.34) is the single most tested calculation in water and wastewater. Get comfortable with it and a whole block of exam questions opens up.
Worked example
Inputs: Flow = 2.0 MGD, Dose or concentration = 8 mg/L.
- lb/day = (flow, MGD) × (concentration, mg/L) × 8.34 lb/gal
- = 2 × 8 × 8.34
- = 133.44 lb/day
The 8.34 is the weight of one gallon of water. Leaving it out is the single most common mistake on this calculation.
When operators use this
Operators use it to convert a target dose in mg/L into an actual chemical feed rate in pounds per day for chlorine, alum, polymer, and lime.
Frequently asked questions
What is the pounds formula?
Pounds per day equals concentration in mg/L times flow in MGD times 8.34, the weight in pounds of one gallon of water.
Where does 8.34 come from?
One gallon of water weighs about 8.34 pounds, so the factor converts a concentration and a daily volume into a daily weight.
Is this free to use?
Yes, completely. No signup and no ads.