Gas pipe sizing chart

This gas pipe sizing chart gives the capacity in CFH of Schedule 40 metallic pipe from 1/2 inch through 4 inch, across every run length from 10 to 200 feet, exactly as published in NFPA 54 Table 402.4(2). Multiply any figure by 1,000 to read it as BTU per hour of natural gas.

Schedule 40 capacity in CFH, natural gas

Find your longest run across the top, your candidate size down the side. The smallest size whose capacity meets your total connected demand is your answer. Round the run up to the next column.

Size	10 ft	20 ft	30 ft	40 ft	50 ft	60 ft	70 ft	80 ft	90 ft	100 ft	125 ft	150 ft	175 ft	200 ft
1/2 inch	172	118	95	81	72	65	60	56	52	50	44	40	37	34
3/4 inch	360	247	199	170	151	137	126	117	110	104	92	83	77	71
1 inch	678	466	374	320	284	257	237	220	207	195	173	157	144	134
1-1/4 inch	1,390	957	768	657	583	528	486	452	424	400	355	322	296	275
1-1/2 inch	2,090	1,430	1,150	985	873	791	728	677	635	600	532	482	443	412
2 inch	4,020	2,760	2,220	1,900	1,680	1,520	1,400	1,300	1,220	1,160	1,020	928	854	794
2-1/2 inch	6,400	4,400	3,530	3,020	2,680	2,430	2,230	2,080	1,950	1,840	1,630	1,480	1,360	1,270
3 inch	11,300	7,780	6,250	5,350	4,740	4,290	3,950	3,670	3,450	3,260	2,890	2,610	2,410	2,240
4 inch	23,100	15,900	12,700	10,900	9,660	8,760	8,050	7,490	7,030	6,650	5,890	5,330	4,910	4,560

Size by appliance and distance

Worked answers for the loads that come up most often, with the math shown on each page:

Furnace (100,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Tankless Water Heater (199,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Water Heater (40,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Gas Range (65,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Gas Dryer (35,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Standby Generator (150,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Pool Heater (250,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft
Fire Pit (60,000 BTU) — 20 ft · 40 ft · 60 ft · 100 ft

Before you cut any pipe

These figures come straight from NFPA 54 Table 402.4(2) for Schedule 40 metallic pipe, natural gas at 0.60 specific gravity, inlet pressure under 2 psi and an allowable pressure drop of 0.5 inches water column. That is the ordinary residential case, and it is the same table the PlumbCalc gas line sizing calculator uses.

Two things change the answer on a real job. First, the code sizes the total connected load on a run, not one appliance in isolation — if a second appliance shares the pipe, add its BTU rating before you size. Second, a 2 psi system, a CSST or copper material, or a longer allowable pressure drop all use different tables entirely. Size to the longest run, size to the full load, and confirm against your local code and the appliance data plate before installing.

How to read the chart on a real job

Measure the run from the meter to the furthest appliance and round up to the next column. Add the BTU ratings of every appliance that shares the pipe and divide by 1,000 for natural gas to get CFH. Read down that column until you reach a capacity that meets your demand, and that is the smallest size the code allows. If nothing in the column is big enough, the run needs engineered sizing or a 2 psi system.

The governing standard is the National Fuel Gas Code, published as NFPA 54 and adopted in most of the United States — see the National Fuel Gas Code for background on the code itself.

Related sizing references

Frequently asked questions

What size gas pipe do I need?

Add the BTU ratings of every appliance on the run, divide by 1,000 for natural gas to get CFH demand, measure the longest run from the meter and round up to the next length column, then pick the smallest size in that column whose capacity meets your demand.

What is the Longest Length Method?

It sizes the whole system against the single longest run from the meter to the furthest appliance, rather than sizing each segment separately. It is conservative, it is simple to apply on site, and it is the method behind this chart.

How many BTU is one CFH?

For natural gas, one cubic foot per hour is about 1,000 BTU per hour, so CFH times 1,000 gives BTU. Propane carries 2,516 BTU per cubic foot, so the same pipe moves far more energy on LP.

Is this chart valid for CSST and copper?

No. This is Schedule 40 metallic pipe. CSST, copper tubing and polyethylene have their own tables, and CSST capacity varies by manufacturer. Always use the table for the material you are installing.

Does a longer run need bigger pipe?

Yes. Capacity falls as the run lengthens because the table is built around a fixed 0.5 inch water column pressure drop, and a longer pipe spends that allowance sooner. A 1 inch line carries 678 CFH at 10 feet but only 195 CFH at 100 feet.

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