You can indeed figure this out using hydraulics formulas.
However, a simpler solution. Run the water into a 5 gallon bucket, and time how long it takes to fill the bucket in seconds.
Use this formula:
Gallons per minute = 300 / TimeToFillBucket
880.57 US gallons per minute
how do i calculate the volumn of backwash in a pool
Find the diameter of the pipe and the pressure and its all simple math after that
1 US gallon = 0.133680556 feet^3
0.00763884 gallons per minute.
Divide it by 60 to get 33.333 gallons per minute.
4.483 US gallons per minute.
The flow would be 2.5 with a meter with 12 inch diameter. This is with a flush at 5.0 FPS.
Use this formula: gallons per minute x 3.785 = liters per minute
96 gallons per minute = about 363.4 liters per minute.
2½-5½ gallons per minute
If there are x number of gallons per second, multiply that number by 60=gallons per minute.