K Factor Calculator
How to Use K Factor Calculator
Calculate K factors for valves, orifices, and other flow restrictions in HVAC and plumbing systems. The K factor relates flow rate to pressure drop across a restriction.
Understanding K Factor
The K factor formula is: K = Q / √(ΔP / SG), where:
- K = Flow coefficient (K factor)
- Q = Flow rate (GPM)
- ΔP = Pressure drop (PSI)
- SG = Specific gravity of fluid
Common Applications
- Control Valves: Sizing valves for HVAC systems
- Balancing Valves: Hydronic system balancing
- Orifice Plates: Flow measurement and restriction
- Pressure Reducing Valves: System pressure control
- Flow Meters: Calibration and sizing
Fluid Properties
| Fluid | Specific Gravity | Temperature |
|---|---|---|
| Water | 1.0 | 68°F (20°C) |
| 30% Glycol | 1.05 | 68°F (20°C) |
| 50% Glycol | 1.09 | 68°F (20°C) |
| Steam (100 psi) | 0.6 | 338°F (170°C) |
Velocity Guidelines
The calculator shows velocity for different pipe sizes to help with system design:
- Recommended velocity: 4-8 ft/s for most applications
- Low velocity (<4 ft/s): May cause air entrapment or settling
- High velocity (>8 ft/s): May cause noise and erosion
- Maximum velocity: 12 ft/s for short runs
Typical K Factors
| Component | Size | Typical K Factor |
|---|---|---|
| Globe Valve (Full Open) | 1" | 5-8 |
| Ball Valve (Full Open) | 1" | 15-25 |
| Balancing Valve | 1" | 2-10 |
| Orifice Plate | 1" | 1-5 |
Calculation Tips
- Always use consistent units (GPM, PSI, specific gravity)
- Account for temperature effects on fluid properties
- Consider viscosity for non-water fluids
- Use manufacturer data when available
- Factor in system operating conditions
- Validate results with field measurements when possible
Cite this page as:
Daniel, P. K Factor Calculator. Available at: https://constructioncalculators.com/k-factor-calculator/. Accessed: October 25, 2026.