Fitting Equivalents Reference
Every K-factor and L/D you need, plus a mini-calc that converts a fitting + diameter into ft and m of equivalent pipe.
Equivalent-length mini-calc
Pick a fitting and a diameter — get the straight-pipe equivalent length immediately.
Equivalent length
5ft
1.524 m · L/D = 30K-factor
0.75—
Source: Crane TP-410Fittings library
Filter by group or type a keyword.
| Fitting | Group | K | L/D | Source | |
|---|---|---|---|---|---|
| Elbow 90° standard (threaded) | Elbows | 0.75 | 30 | Crane TP-410 | |
| Elbow 90° long radius | Elbows | 0.45 | 20 | Crane TP-410 | |
| Elbow 45° | Elbows | 0.35 | 16 | Crane TP-410 | |
| Tee — flow through run | Tees | 0.4 | 20 | Crane TP-410 | |
| Tee — flow through branch | Tees | 1.8 | 60 | Crane TP-410 | |
| Gate valve fully open | Valves | 0.17 | 8 | Crane TP-410 | |
| Gate valve half open | Valves | 4.5 | 200 | Crane TP-410 | |
| Globe valve fully open | Valves | 6 | 340 | Crane TP-410 | |
| Ball valve fully open | Valves | 0.05 | 3 | Cameron Hydraulic Data | |
| Check valve — swing | Valves | 2 | 100 | Crane TP-410 | |
| Check valve — lift | Valves | 12.5 | 600 | Crane TP-410 | |
| Butterfly valve fully open | Valves | 0.7 | 40 | Crane TP-410 | |
| Sudden expansion (1:2) | Transitions | 0.56 | 28 | Idel’chik (Borda–Carnot) | |
| Sudden contraction (2:1) | Transitions | 0.34 | 17 | Idel’chik | |
| Pipe entrance — sharp edged | Entry / Exit | 0.5 | 25 | Crane TP-410 | |
| Pipe entrance — rounded | Entry / Exit | 0.05 | 3 | Crane TP-410 | |
| Pipe exit (to tank) | Entry / Exit | 1 | 50 | Crane TP-410 | |
| Elbow 90° mitred (welded segments) | Elbows | 1.2 | 60 | Crane TP-410 | |
| Plug valve fully open | Valves | 0.4 | 18 | Crane TP-410 | |
| Diaphragm valve fully open | Valves | 2.3 | 115 | Crane TP-410 | |
| Foot valve with strainer (poppet disc) | Valves | 1.4 | 75 | Crane TP-410 | |
| Angle valve fully open | Valves | 2 | 145 | Crane TP-410 | |
| Eccentric reducer (suction-side, prevents air pocket) | Transitions | 0.4 | 18 | Cameron Hydraulic Data | |
| Concentric reducer (gradual, 30° taper) | Transitions | 0.2 | 10 | Cameron Hydraulic Data | |
| Y-strainer (clean basket) | Meters / Strainers | 2.5 | 125 | Manufacturer typical (clean); doubles when dirty | |
| Orifice plate flow meter (β=0.6) | Meters / Strainers | 4 | 200 | ISO 5167 typical for β = 0.6 |
How this works
K-factor method: hm = K · v² / (2g) Equivalent length method: hm = f · (Leq/D) · v² / (2g) where Leq = (L/D) · D
Both methods are equivalent in the fully turbulent regime. The two-coefficient table here means you can use whichever method matches your existing calc. Don't apply both to the same fitting — you'd double count.
| K-factor | Equivalent length | |
|---|---|---|
| Form | h = K · v²/2g | L_eq = (L/D)·D added to pipe length |
| Pipe-friction-factor sensitive? | No | Yes — depends on f |
| Best for | Hand calc on a single fitting | When you already run Darcy-Weisbach on the pipe |
| Combine? | Per fitting, not both | Per fitting, not both |
Common questions
K-factor or equivalent length — which should I use?
Both are valid. K-factor (h = K · v² / 2g) is more accurate at large Reynolds where the loss is dominated by velocity head. Equivalent length (treat the fitting as more pipe of length L_eq) is convenient when you are already running Darcy-Weisbach. Most textbooks recommend not mixing them on the same fitting — pick one method per fitting.
Where do these numbers come from?
Crane Technical Paper TP-410 is the industry reference and the source of most values here. Cameron Hydraulic Data and Idel'chik provide cross-checks for transitions. Manufacturer Cv values are more accurate when available — they should override the table for safety-critical work.
Are these values valid for non-water fluids?
Yes for incompressible Newtonian fluids in the fully turbulent regime, where K and L/D become roughness-dominated. They are not strict for very viscous fluids in laminar regimes; for those cases, a more rigorous approach is needed.