Pipe Fittings Loss Calculator (K Values)
The head and pressure lost in elbows, tees, valves and other fittings in a pipe line.
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How this calculator works
Every fitting disturbs the flow and loses pressure. The loss is written as a loss coefficient K times the velocity head, v² / 2g. Add up the K values of all the fittings for the total, then multiply by the velocity head to get the head loss in metres of the liquid.
The K values here are typical figures for fully turbulent flow in steel fittings. The real value depends on the size, the maker and the flow, so use the manufacturer's data when you have it. Add this to the pipe friction loss to get the total the pump must overcome.
Formulas used
- \sum K
- h = \sum K\,\frac{v^2}{2g}
- \Delta p = \sum K\,\frac{\rho v^2}{2}
Worked example
With the default numbers in the calculator above:
- Total loss coefficient: 7.3
- Head loss: 1.488 m
- Pressure loss: 14.57 kPa
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
Why is a globe valve K so high?
The flow has to turn several times through the valve body, so a fully open globe valve loses about 30 times what a gate valve does.
Does the pipe friction count too?
Yes, separately. Use the pipe pressure drop calculator for the straight pipe and add the two.
Are the values for all sizes?
They are typical for common sizes in turbulent flow. Very small fittings and slow or viscous flow can differ a lot.
Related calculators
Further reading: White, Fluid Mechanics; Munson, Young and Okiishi, Fundamentals of Fluid Mechanics; Crane Technical Paper 410. Crane Technical Paper 410 for the K method.
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