Pipe flow calculators

Resistance coefficient K calculator


Calculator Description

Calculator can be used for resistance coefficient (or resistance factor) K and equivalent length l/d calculation for valves and fittings.

  • Calculate:

    • Resistance coefficient K
  • Select:

    • Fitting type
    • Fitting shape and diameter

Calculator Features

  • Applicable for bends, tees, reducers, entrance and exits
  • For liquids and gases

Resistance coefficient and equivalent length l/d calculator should be used with pressure drop calculator or with gas compressible flow calculator to calculate pressure drop in piping system that includes obstructions like fittings and valves.

Based on the size and shape of valves and fittings different values for resistance coefficient and equivalent length l/d are calculated. Calculator can be used for elbows, pipe bends, mitre bends, return bends, standard tee, pipe entrance, pipe exit and for sudden and gradual enlargement or contraction of pipe.


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If you would like to use the calculator, but actually can't see the blue CALCULATOR button in the upper left part of the page than please read instructions.

Q: Calculate resistance coefficient K for 90O 1 inch elbow with radius to diameter ratio R/D = 1.5

A: Calculation setup:
Input values:
R/D = 1.5
D = DN25
n = 1

Q: Calculate resistance coefficient for fluid flowing from resevoir to pipeline with pipe inward projecting to reservoir

A: Calculation setup:
Input values:
Type = inward projecting

Q: Calculate resistance coefficient for gradual enlargement and contraction. Angle of reducer is 300. Pipe diameters are 100 mm and 150 mm.

A: Calculation setup:
Input values:
Alfa = 300
D1 = 100 mm
D2 = 150 mm

Resistance coefficient value is used for pressure drop calculation using following formula:

Read more about used theory on flow in pipes page.

If you experience problems with calculator start try to find answers on instructions page.

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