LP / Propane Pipe Sizing Chart
Schedule 40 propane pipe capacity by size and developed length, per NFPA 58. Capacities are in MBH (thousands of BTU/hr) at 11 in. w.c. inlet with a 0.5 in. w.c. pressure drop — the common residential condition. Because propane packs about 2,500 BTU per cubic foot, its tables differ from natural gas.
Schedule 40 propane capacity (MBH)
| Length | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" |
|---|---|---|---|---|---|
| 10 ft | 291 | 608 | 1146 | 2353 | 3525 |
| 20 ft | 200 | 418 | 788 | 1617 | 2423 |
| 40 ft | 137 | 287 | 541 | 1111 | 1665 |
| 60 ft | 110 | 231 | 435 | 892 | 1337 |
| 80 ft | 94 | 198 | 372 | 764 | 1144 |
| 100 ft | 84 | 175 | 330 | 677 | 1014 |
Why propane gets its own tables
Two properties set propane apart. It carries about 2.4 times the energy of natural gas per cubic foot, so the same BTU load flows as far less gas — which would suggest smaller pipe. But propane is also more than twice as dense (specific gravity 1.52 versus 0.60), which increases the pressure drop for a given flow. The net of those two effects is baked into the propane-specific tables, which is why you never size a propane run off a natural gas chart. Get the connected load from the appliance BTU demand chart and size the longest run against this table. For the natural gas equivalent, see the natural gas pipe sizing chart.
Common questions
How is propane pipe sizing different from natural gas?
Propane carries much more energy per cubic foot — about 2,500 BTU/cu ft versus 1,030 for natural gas — so a propane system moves roughly 2.4 times less volume for the same BTU load. But propane is also heavier (specific gravity 1.52 vs 0.60), so it uses its own sizing tables, not the natural gas ones. This chart is Schedule 40 metallic pipe at the common residential low-pressure condition.
What pressure does this propane table assume?
It assumes 11 inches of water column at the inlet with a 0.5 in. w.c. pressure drop — the standard condition downstream of the second-stage regulator to the appliances in a residential system. Higher-pressure propane runs between the first and second regulators use a different, much larger-capacity table; do not mix them up.
How do I convert a BTU load to size the pipe?
Total the connected appliance load in BTU/hr, then work the longest-length method against this table. For a volume-based table you would divide by the heating value — 100,000 BTU/hr of propane is 40 CFH — but this table is already in MBH (thousands of BTU/hr), so you read the load against it directly.
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