Do these lengths apply to every material?

The tabulated values are for steel sch40 at a C-factor of 120. For any other C-factor, multiply by the correction in the table above. The material also has to match the fitting: a grooved coupling and a threaded elbow of the same nominal size are not interchangeable.

Do I count the fitting at both ends of a pipe?

Count each fitting once, on the pipe it belongs to. Where two runs meet at a tee, the tee's branch equivalent length goes on the branch and the run length goes on the through pipe.

Why are some cells empty?

The chart prices each fitting only in the sizes the standard lists it for. An empty cell means there is no tabulated value, not that the fitting has no loss — take that figure from the manufacturer's listing.

Are these lengths a code requirement?

The equivalent-length method is what NFPA 13 prescribes, and the tabulated values come from the standard. Some manufacturers publish their own figures for listed fittings, which the authority having jurisdiction may accept or require.

How do I use an equivalent length?

Add it to the physical length of the pipe, then run the total through Hazen-Williams. A pipe with 40 ft of run and 12 ft of fittings is calculated as 52 ft.

Equivalent length of fittings table

Equivalent pipe length for fittings and valves by size, with the C-factor correction.

Preliminary. The reference tables behind this calculation are pending a second check against their printed source. Verify against your adopted edition before using a result in a submitted calculation.

Equivalent lengths are feet of schedule 40 steel pipe at C = 120. Multiply by the factor for another C. Fittings the chart does not price are listed separately; take those from the manufacturer.

An empty cell is not a zero. It means the chart does not price that fitting at that size — take the value from the manufacturer’s listing and enter it as the pipe’s equivalent length. The chart prices nothing at 1/2 in, so that size is not shown.

Equivalent length in feet, by nominal size in inches.
Fitting	3/4	1	1-1/4	1-1/2	2	2-1/2	3	3-1/2	4	5	6	8	10	12
Butterfly valve	n/l	n/l	n/l	n/l	6	7	10	n/l	12	9	10	12	19	21
Check valve	n/l	5	7	9	11	14	16	19	22	27	32	45	55	65
45° elbow	1	1	1	2	2	3	3	3	4	5	7	9	11	13
90° standard elbow	2	2	3	4	5	6	7	8	10	12	14	18	22	27
90° long-turn elbow	1	2	2	2	3	4	5	5	6	8	9	13	16	18
Gate valve	n/l	n/l	n/l	n/l	1	1	1	1	2	2	3	4	5	6
Swing check valve	n/l	5	7	9	11	14	16	19	22	27	32	45	55	65
Tee or cross, flow turned 90°	3	5	6	8	10	12	15	17	20	25	30	35	50	60

C-factor multipliers

The lengths above are stated for pipe at C = 120. On any other pipe, multiply. A CPVC system carries roughly half again the fitting length a steel one does, which is easy to forget and moves the answer.

C-factor	Multiplier
100	0.713
120	1
130	1.16
140	1.32
150	1.51

The formula

L_eq = L_table · m(C)

L_eq: equivalent length to add to this pipeft
L_table: tabulated length at C = 120ft
m(C): the multiplier for the pipe's C-factor

Which pipe a reducing fitting belongs to

Where a fitting changes size, the equivalent length is taken for the smaller of the two pipes and added to that pipe’s run. The full app applies this automatically and flags a size that steps down in the wrong direction, because a reducer pointing the wrong way is a mistake a hand calculation rarely catches.

Fittings this chart does not price

Alarm valve: Not listed in the equivalent-length chart. Take the loss from the manufacturer's listing and enter it as the pipe's equivalent length.
Dry pipe valve: Not listed in the equivalent-length chart. Take the loss from the manufacturer's listing and enter it as the pipe's equivalent length.

Run the whole system, not one pipe. Same solver, pass or fail against your flow test, NFPA 13 report as a PDF.

Try the full calc

Questions about this calculation

Do these lengths apply to every material?: The tabulated values are for steel sch40 at a C-factor of 120. For any other C-factor, multiply by the correction in the table above. The material also has to match the fitting: a grooved coupling and a threaded elbow of the same nominal size are not interchangeable.
Do I count the fitting at both ends of a pipe?: Count each fitting once, on the pipe it belongs to. Where two runs meet at a tee, the tee's branch equivalent length goes on the branch and the run length goes on the through pipe.
Why are some cells empty?: The chart prices each fitting only in the sizes the standard lists it for. An empty cell means there is no tabulated value, not that the fitting has no loss — take that figure from the manufacturer's listing.
Are these lengths a code requirement?: The equivalent-length method is what NFPA 13 prescribes, and the tabulated values come from the standard. Some manufacturers publish their own figures for listed fittings, which the authority having jurisdiction may accept or require.
How do I use an equivalent length?: Add it to the physical length of the pipe, then run the total through Hazen-Williams. A pipe with 40 ft of run and 12 ft of fittings is calculated as 52 ft.

The other calculators

How these results are checked against worked examples · Pricing for the full app

Updated 2026-09-07