Flow Rate Calculator
Calculate flow rate from pipe parameters and convert between common flow units.
Flow Rate Formulas
Flow from Velocity
Q (GPM) = V × A × 448.831
Where:
V = Velocity (ft/s)
A = Pipe cross-sectional area (ft²)
A = π × (D/24)² for diameter D in inches
Where:
V = Velocity (ft/s)
A = Pipe cross-sectional area (ft²)
A = π × (D/24)² for diameter D in inches
Common Unit Conversions
- 1 GPM = 3.785 LPM (liters per minute)
- 1 GPM = 0.134 CFM (cubic feet per minute)
- 1 GPM = 0.227 m³/hr (cubic meters per hour)
- 1 GPM = 60 GPH (gallons per hour)
- 1 LPM = 0.0167 L/s (liters per second)
Velocity Guidelines
Water velocity affects noise, pipe erosion, and system longevity:
- Recommended: 4-6 ft/s for most residential applications
- Maximum: 8 ft/s for copper/plastic, 5-6 ft/s for steel/iron
- Minimum: 2 ft/s to prevent sediment buildup