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Pipe Fitting K-Factor Table (Crane TP-410)

Resistance coefficients (K) for valves and fittings, from Crane Technical Paper 410. K sets the minor pressure loss of a fitting via hL = K·V²/2g. Crane expresses K as n · fT — a fixed L/D equivalent (n) times the fully-turbulent friction factor (fT) for the pipe size. Use the tables below to look up n and fT, or let SimuPipe compute Crane K automatically.

The Minor-Loss Equation
hL=K V22gΔP=K 12ρV2K=n fTh_L = K \, \frac{V^2}{2g} \qquad \Delta P = K \, \tfrac{1}{2} \rho V^2 \qquad K = n \, f_T
  • KK — resistance coefficient, VV — mean velocity
  • nn — L/D equivalent for the fitting (from the table), fTf_T — turbulent friction factor for the size
  • ρ\rho — fluid density, gg — gravitational acceleration

Total loss in a line = straight-pipe friction (Darcy-Weisbach) + the sum of all fitting K-factors × velocity head.

Resistance Coefficients (K = n · f_T)
Fitting / valven (L/D)K @ 2″ (f_T 0.019)
Bends & elbows
90° standard elbow300.57
90° long-radius elbow160.30
45° standard elbow160.30
180° return bend (close pattern)500.95
Tees
Tee — flow through run (line)200.38
Tee — flow through branch601.14
Valves (full open)
Gate valve80.15
Globe valve3406.46
Angle valve1502.85
Ball valve (full bore)30.06
Butterfly valve (2–8")450.86
Plug valve (straightway)180.34
Swing check valve1001.90
Lift check valve60011.4

Representative Crane TP-410 values — exact K varies by fitting construction (e.g. globe-valve seat type) and standard. Consult Crane TP-410 for the authoritative, complete set.

These K-factors are for fully open valves. For a throttling or control valve, size it by flow coefficient instead of a single K — use the control valve Cv / Kv sizing calculator.

90° and 45° Elbow K-Factors by Pipe Size

A standard 90° elbow has a Crane TP-410 K-factor of about 0.4 to 0.8 (≈ 0.57 at 2″ pipe). A long-radius 90° elbow is roughly half that — 0.2 to 0.43, about 0.30 at 2″ and dropping to ≈ 0.2 in large 12–16″ pipe. A 45° elbow matches the long-radius 90° at ≈ 0.2 to 0.43. K rises in smaller pipe because K = n·fT and the turbulent friction factor fT is higher at small sizes.

Elbow type½"1"2"4"6"8–10"12–16"
90° standard elbow0.810.690.570.510.450.420.39
90° long-radius elbow0.430.370.300.270.240.220.21
45° elbow0.430.370.300.270.240.220.21

K = n·fT with n = 30 (90° standard) or 16 (90° long-radius and 45°). Nominal pipe size, clean commercial steel.

Turbulent Friction Factor f_T by Size
Nominal sizef_T (clean steel)
1/2"0.027
1"0.023
2"0.019
4"0.017
6"0.015
8–10"0.014
12–16"0.013

Multiply the fitting's n by f_T for your size to get K. Example: a 90° elbow (n = 30) in 6″ pipe → K = 30 × 0.015 = 0.45.

Entrance & Exit Coefficients (direct K)
FeatureK
Pipe entrance — inward projecting (Borda)0.78
Pipe entrance — sharp-edged (flush)0.50
Pipe entrance — slightly rounded0.23
Pipe entrance — well-rounded0.04
Pipe exit (into a tank or atmosphere)1.0

These are direct K values (not scaled by f_T). Sudden contractions and enlargements instead depend on the diameter ratio β = d/D — a sudden enlargement is K = (1 − β²)² referenced to the upstream velocity.

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Frequently Asked Questions

What is a pipe fitting K-factor?
The K-factor (resistance or loss coefficient) is a dimensionless number that quantifies the minor pressure loss caused by a fitting, valve, bend, or other disturbance to flow. The head loss across the fitting is K times the velocity head: h_L = K·V²/(2g). A higher K means more loss — a globe valve (K ≈ 6 at 2 inch) loses far more than a gate valve (K ≈ 0.15) at the same flow.
What is the K-factor of a 90° elbow?
A standard 90° elbow has a Crane TP-410 K-factor of about 0.4 to 0.8 — roughly 0.57 in 2-inch pipe, higher in smaller pipe and lower in larger pipe (K = n·f_T with n = 30). A long-radius 90° elbow is about half that: 0.2 to 0.43, around 0.30 at 2 inch and dropping to about 0.2 in large 12–16 inch pipe (n = 16). A 45° elbow matches the long-radius 90° at roughly 0.2 to 0.43.
How do I use K-factors to calculate pressure loss?
Compute the velocity head ½ρV² (or V²/2g for head), then multiply by the sum of all the fitting K-factors in the line: ΔP = (ΣK)·½ρV². Add this minor loss to the straight-pipe (Darcy-Weisbach) friction loss to get the total. SimuPipe does both automatically — each fitting contributes its K and the solver sums them with the pipe friction.
What is the Crane TP-410 K = n·f_T method?
Crane Technical Paper 410 expresses each valve and fitting's resistance as K = n·f_T, where n is a fixed L/D equivalent length ratio for that fitting type (e.g. 30 for a 90° elbow, 340 for a globe valve) and f_T is the fully-turbulent friction factor for clean commercial steel at that pipe size. You look up n from the fitting table and f_T from the size table, then multiply. This makes the same fitting give a slightly different K in different pipe sizes.
Why does the K-factor depend on pipe size?
Because f_T depends on size: smaller pipe has a higher fully-turbulent friction factor (about 0.027 at ½ inch versus 0.013 at 12–16 inch). Since K = n·f_T, the same fitting has a higher K in small pipe than in large pipe. The entrance and exit coefficients are the exception — they are direct K values that don't scale with f_T.
What is the difference between K-factor and equivalent length?
Both express minor losses, just in different forms. Equivalent length (L/D or Le) replaces a fitting with a length of straight pipe that would cause the same loss; the K-factor gives the loss directly as a multiple of velocity head. They are related by K = f·(L/D), and in the Crane method n is exactly that L/D ratio. K-factors are generally more accurate because they don't assume the fitting's loss tracks pipe friction.
What K-factor should I use for a partially open valve?
The values here are for fully open valves. As a valve closes, its resistance rises steeply — a globe valve at 50% travel can have many times its full-open K. For throttling and control valves, size with the flow coefficient (Cv/Kv) and its flow characteristic rather than a single K — see our Cv/Kv conversion table and valve sizing calculator.

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