Gas Pipe Sizing Calculator

Every gas appliance has a BTU input, every run has friction, and the pipe is the only thing in between. Over-size and you waste steel; under-size and the appliance starves at the far end.

Gas Pipe Sizing Calculator uses the longest-run method with a standard natural gas capacity table to pick the pipe size.

• Load-based: Total CFH from appliance inputs.
• Longest-run: Sizes the worst branch.
• Table driven: Standard steel pipe capacity.
• BTU view: CFH and BTU/h together.
• Live update: Results while you type.
• Export: Text, CSV or JSON report.

1. Enter total appliance load in BTU/h or CFH.
2. Enter longest run in feet.
3. Pick inlet pressure and adjust specific gravity.
4. Read the pipe size and its capacity.
5. Export the result if needed.

Example 1. A 150,000 BTU/h total with a 60-foot longest run at 0.5 psi picks a 1-inch line running 260 CFH - plenty of headroom.

Example 2. Push that same load to 200 feet and the pipe must grow to 1-1/4 inch; friction over distance is what drives the size, not the load alone.

• Table correct: Standard natural gas steel table.
• Longest run: Covers every branch.
• Dual units: CFH and BTU/h.
• Free and private: No uploads, no logging.