Natural Gas Pipe Sizing Calculator
Pipe diameter for BTU load and run length.
Enter your values
ⓘ Live results
Results
- Recommended pipe size
- 3/4 in
- Load in cubic feet/hr
- 150 CFH
- Capacity at this length
- 180 CFH
- Headroom
- 20%
- Appliances
- 3
Quick answer
Gas pipe is sized by total BTU load and the longest run; capacity falls as length grows, so a 100 ft run needs a larger pipe than a 20 ft run.
size from BTU ÷ length capacity table
How to use the Natural Gas Pipe Sizing Calculator
- 1Add up the BTU rating of every appliance on the run.
- 2Measure the longest run from the meter to the furthest appliance.
- 3Use the recommended size or larger — never smaller.
Worked example
Using the values the calculator loads with:
Inputs
- Total load150000 BTU/hr
- Longest run40 ft
- Appliances on the run3
Results
- Recommended pipe size3/4 in
- Load in cubic feet/hr150 CFH
- Capacity at this length180 CFH
- Headroom20%
- Appliances3
Frequently asked questions
How many BTU can a 1/2 inch gas line carry?
About 172,000 BTU at 10 ft, dropping to roughly 95,000 BTU at 40 ft on natural gas at 0.5 in WC.
Do I size by total load or longest run?
Both — capacity tables are read using the total connected load against the longest run distance.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.