Operator math, worked
How to convert flow: GPM, GPD, and MGD
Flow shows up in three units on the exam: gallons per minute (GPM), gallons per day (GPD), and million gallons per day (MGD). Converting between them is just multiplying or dividing by 1,440 and 1,000,000.
Last reviewed 2026-08-04
The formula
GPD = GPM x 1,440 and MGD = GPD / 1,000,000
The steps
GPM to GPD
Multiply gallons per minute by 1,440, the number of minutes in a day.
GPD to MGD
Divide gallons per day by 1,000,000, because MGD is millions of gallons.
Worked example
A pump runs at 250 GPM. What is that in GPD and MGD?
- GPD: 250 x 1,440 = 360,000 GPD
- MGD: 360,000 / 1,000,000 = 0.36 MGD
Answer: 360,000 GPD, or 0.36 MGD
Common questions
- Why 1,440?
- There are 1,440 minutes in a day, so it turns per-minute into per-day.
- How do I go from MGD back to GPM?
- Multiply MGD by 1,000,000 for GPD, then divide by 1,440 for GPM.
- Which unit does the pounds formula use?
- MGD, million gallons per day.