Piping
Minor Loss / K-Value Loss Calculator
Minor losses are pressure and head losses caused by fittings, valves, bends, and other flow obstructions in a piping system. This calculator determines the head loss and pressure drop from a user-supplied K-value (loss coefficient). The K-value must be entered by the user — no fitting database or K-value lookup is included.
TypeInteractive calculator — separate from unit conversions
Calculator
Pressure:
Head:
Result
Minor head loss (h_K)0.407886 m
Minor pressure loss (ΔP_K)4 kPa
Velocity head (v²/(2g))0.203943 m
Dynamic pressure (ρv²/2)2 kPa
Formulas
Minor head loss
h_K = K × v²/(2g)
Minor pressure loss
ΔP_K = K × ρv²/2
Velocity head
v²/(2g)
Dynamic pressure
ρv²/2
Diagram
Worked example
A 90° elbow has K = 0.9. Water (ρ = 998 kg/m³) flows at 3 m/s. g = 9.80665 m/s².
- 01Velocity head = v²/(2g) = 9 / 19.6133 = 0.4589 m
- 02h_K = K × v²/(2g) = 0.9 × 0.4589 = 0.4130 m
- 03ΔP_K = K × ρv²/2 = 0.9 × 998 × 9 / 2 = 4,042 Pa ≈ 4.04 kPa
Result
Minor head loss is 0.4130 m. Minor pressure loss is 4,042 Pa (4.04 kPa).
FAQ
Does this look up K-values for fittings?
No. You must supply the K-value directly. For K-values of specific fittings, consult Crane TP-410 or your fitting manufacturer's data.
Does this select fittings for me?
No. This calculator requires a user-supplied K-value. No fitting selection or fitting library is included.
Is this a control valve sizing calculator?
No. Control valve sizing (Cv/Kv) is a separate discipline with its own equations and is not implemented here.
Does K depend on Reynolds number?
Some K-values vary with Reynolds number, particularly in laminar flow. This calculator does not apply Reynolds-dependent K corrections.