Minor Loss from K Factor
Also known as fitting loss · K value loss
Worked example: 1.2 m lost at 3 m/s → K = 2.6151. Press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Change any unit and the answer follows.
Where Minor Loss from K Factor fits
- Pipe friction losses9 formulas
- Valve sizing coefficients4 formulas
See also
Darcy–Weisbach Head Loss: Both use minor head loss and flow velocity.Equivalent Length of a Fitting: Both use Resistance coefficient.Hazen–Williams Head Loss: Both use minor head loss.Net Positive Suction Head Available (NPSHa): Both use minor head loss.Total Dynamic Head: Both use minor head loss.Hydraulic Gradient: Both use minor head loss.Minor losses →
UniversityFluid Mechanics, HVAC & Refrigeration
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Minor Loss from K Factor explained
Every disturbance a fitting imposes on the flow (the sudden turn of an elbow, the contraction through a gate seat, the wake behind a tee) dissipates some multiple of the velocity head. That multiple is K. The US EPA's EPANET 2.2 User Manual gives typical values: 0.9 for a short-radius elbow, 0.2 for a fully open gate valve, 10 for a fully open globe valve, 0.5 for a square entrance, 1.0 for the exit into a tank. Water at 8 ft/s through that elbow loses 0.9 × 64/64.35 ≈ 0.90 ft.
Calling these "minor" losses is a historical joke that has misled generations. In a long transmission main they truly are minor, but in a chiller room or a pump skid (twenty elbows, four valves and a strainer in thirty feet of pipe) they dominate, often carrying three-quarters of the total loss. The other subtlety is the velocity: K is referenced to the velocity in the pipe of the fitting's nominal size, so for a reducing fitting you must be clear which of the two velocities the tabulated K assumes.
Minor Loss from K Factor formula
- = Minor head loss (m)
- = Resistance coefficient
- = Flow velocity (m/s)
Pipe friction losses
9 formulasDarcy–Weisbach, Hazen–Williams, friction factors, minor losses and equivalent length — every way the trade computes head loss in pipe.
Valve sizing coefficients
4 formulasCv, Kv, K factors and equivalent length — the four coefficients that turn a valve or fitting into a pressure drop at a given flow.
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formula.expert. (2026, November 8). Minor Loss from K Factor Formula & Calculator. https://formula.expert/solvers/minor-loss-k-factor
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