Pipe Fitting K-Values Reference
Reference-style typical resistance coefficient (K) values for common fittings and valves used with minor-loss calculations. Preliminary values only — geometry, size, Reynolds number, and valve opening all matter. Pairs with the Minor Loss calculator.
Caution — preliminary values only
These are typical, representative K-values for preliminary use.
They are not a substitute for project standards, Crane TP-410, Idelchik, or vendor data, or for detailed hydraulic design. K-values vary with geometry, size, Reynolds number, valve opening, fitting standard, and installation. For anything beyond a preliminary estimate, use the value from the governing source for the specific fitting.
Purpose
The resistance coefficient (K) expresses the minor (local) head loss of a fitting or valve as a multiple of the velocity head: h_L = K × v² / (2g). The Minor Loss calculator deliberately takes K as a user input rather than carrying a built-in database — this reference fills that gap with typical values you can enter, so the calculator and your fitting list become a connected workflow.
Typical K-values (dimensionless)
Values are representative ranges for turbulent flow in common commercial fittings. Treat the range as preliminary and confirm against the governing source.
| Fitting / valve | Typical K |
|---|---|
| Elbow, 90° standard (threaded) | 0.7 – 1.5 |
| Elbow, 90° long-radius (flanged) | 0.2 – 0.4 |
| Elbow, 45° standard | 0.3 – 0.4 |
| Return bend, 180° | 0.8 – 1.5 |
| Tee, flow through run | 0.1 – 0.6 |
| Tee, flow through branch | 1.0 – 2.0 |
| Gate valve, fully open | 0.1 – 0.2 |
| Globe valve, fully open | 6 – 10 |
| Ball valve, fully open | 0.05 – 0.1 |
| Butterfly valve, fully open | 0.3 – 1.5 |
| Swing check valve | 2 – 3 |
| Sharp-edged entrance | ≈ 0.5 |
| Rounded entrance | 0.04 – 0.2 |
| Exit (pipe to tank) | ≈ 1.0 |
| Sudden contraction (severe) | up to ≈ 0.5 |
| Sudden expansion (to large vessel) | ≈ 1.0 |
Entrance/exit and expansion/contraction K-values are referenced to the relevant pipe velocity; check which velocity head a given source uses before combining values.
Units
- •K — dimensionless resistance coefficient.
- •v — velocity in m/s; g = 9.80665 m/s²; resulting loss h_L in metres (m). Convert with metres → feet.
Assumptions
- •Fully turbulent, single-phase flow of a Newtonian liquid.
- •Valves fully open unless stated; partial opening raises K sharply.
- •Standard commercial fittings; cast, fabricated, or mitred fittings differ.
Boundaries and exclusions
- •Typical preliminary values only — not project standards or certified data.
- •Not a substitute for Crane TP-410, Idelchik, or vendor Cv/K data.
- •K varies with geometry, size, Reynolds number, valve opening, and fitting standard.
- •This page does not change the Minor Loss calculator scope — K remains a user input there.
How to use in calculations
Sum the K-values for every fitting and valve on the line, then enter the total (or each item) into the Minor Loss calculator together with the pipe velocity to get the minor head loss. Add that to the straight-pipe friction loss from the Pipe Head Loss or Darcy-Weisbach calculator to build the system head used in pump sizing. K must still be entered by the user — confirm each value against the governing source for the actual fitting.
Source / context notes
- •Crane Technical Paper No. 410 (TP-410) — Flow of Fluids Through Valves, Fittings, and Pipe
- •I.E. Idelchik — Handbook of Hydraulic Resistance
- •Perry's Chemical Engineers' Handbook — fluid-flow minor-loss tables
Ranges shown are typical representative values for orientation. Use the governing source value for the specific fitting and standard in any real calculation.