Gas Size Calculator
Enter the total BTU per hour of the appliances, the length of the longest pipe run and the gas type. The calculator picks the smallest Schedule 40 steel pipe that carries the load.
- Gas pipe size
- Flow
- Capacity
Use the longest run from the meter to the furthest appliance.
Natural gas carries about 1,000 BTU per cubic foot. A 150,000 BTU/h load on a 40 ft run of natural gas needs 150 cfh. A 3/4 in pipe carries about 170 cfh at that length, enough, while 1/2 in carries only 81.
Gas pipe sizing chart
Natural gas, Schedule 40, 0.5 in w.c. drop. Search for a size.
| Pipe | 10 ft | 20 ft | 40 ft | 100 ft |
|---|---|---|---|---|
| 1/2 in | 172 | 118 | 81 | 50 |
| 3/4 in | 360 | 248 | 170 | 104 |
| 1 in | 678 | 466 | 321 | 196 |
| 1-1/4 in | 1390 | 956 | 658 | 401 |
| 1-1/2 in | 2090 | 1437 | 989 | 603 |
| 2 in | 4020 | 2765 | 1902 | 1159 |
Thousand BTU/h.
Run length and pipe
150,000 BTU/h. Slide the length.
The pipe is drawn to the appliance.
How to size a gas pipe
Load to pipe. Step through it.
Load
Add appliance BTU.
Pressure test new gas pipe before use.
Steel, CSST or copper
Gas pipe types. Compare them.
Traditional.
Flexible.
Some areas.
CSST must be bonded to earth.
Before you install
Gas checks. Tick each item.
Tick each item as you go.
Only licensed fitters should work on gas lines.
What you get
Gas pipe sizing. Each tile explains one result.
Pipe.
BTU.
cfh.
Run.
At length.
A pipe too small starves appliances at full fire.
Frequently Asked Questions
No question matches that search.
What size gas pipe do I need?
Add up the BTU load and use the code table at the longest run length.
How many BTU can a half inch gas pipe carry?
About one hundred and seventy thousand at ten feet, less on longer runs.
How do I convert BTU to cubic feet?
Divide by about one thousand for natural gas.
Does propane need a smaller pipe?
Yes. It carries more energy per cubic foot.
Why does length matter?
Longer pipes lose more pressure, so they carry less gas.
Can I size gas pipe myself?
You can estimate it, but a licensed fitter must install and test it.
Gas that keeps up
Size the pipe to the load and every burner gets full flame.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.