Natural Gas Pipe Sizing Calculator
Pipe diameter for BTU load and run length.
Enter your values
Enter the total load in BTU/hr.
Enter the longest run in ft.
Enter the appliances on the run you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Pipe diameter for BTU load and run length. |
|---|---|
| Category | Engineering |
| Inputs needed | Total load, Longest run, Appliances on the run |
| Main output | Recommended pipe size |
| Formula | size from BTU ÷ length capacity table |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Total load(BTU/hr)
- Enter the total load in BTU/hr.
- Longest run(ft)
- Enter the longest run in ft.
- Appliances on the run
- Enter the appliances on the run you are working with.
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.
What do I need to enter into the Natural Gas Pipe Sizing Calculator?
Just 3 values: total load, longest run, appliances on the run. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Natural Gas Pipe Sizing Calculator work out the 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. It applies the formula size from BTU ÷ length capacity table and shows the working so you can check each step by hand.
Is the Natural Gas Pipe Sizing Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.