Operator math, worked
How to calculate flow rate from volume and time
Flow rate is how much water moves in a set time. Divide the amount by the time. Gallons divided by minutes gives gallons per minute; gallons divided by days gives gallons per day.
Last reviewed 2026-08-04
The formula
flow = amount / time
The steps
Write the amount and the time
Note how many gallons moved and how long it took.
Divide amount by time
Divide the gallons by the time. The unit of the answer matches the time unit you used.
Match the unit they ask for
If they want GPM, use minutes; if they want GPD, use days.
Worked example
A tank fills with 6,000 gallons in 30 minutes. What is the flow in GPM?
- 6,000 / 30 = 200
Answer: 200 GPM
Common questions
- How do I get gallons per minute?
- Divide the gallons by the number of minutes it took.
- What decides the answer's unit?
- The time unit you divide by. Minutes give GPM; days give GPD.
- Is this the same as flow conversions?
- It is the first step. Once you have the flow, you can convert between GPM, GPD, and MGD.