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Gas Pipe Calculator · Free Tool

Gas Pipe
Sizing Calculator

Size natural gas and propane supply lines for furnaces, water heaters, and appliances. Based on IFGC pipe sizing tables.

Gas Pipe Sizing for HVAC

Undersized gas lines cause low gas pressure at the appliance, leading to poor performance, incomplete combustion, and nuisance lockouts. This calculator uses IFGC capacity tables to recommend the correct pipe diameter.

Common Furnace Gas Pipe Sizes

Most residential furnaces (60,000-100,000 BTU) need a 1/2" or 3/4" gas line for runs under 50 feet. Runs over 50 feet or multiple appliances on the same line typically need 3/4" or 1".

Frequently Asked Questions

What size gas line for a 100,000 BTU furnace?
For runs under 30 feet, 1/2" is often sufficient. For 30-50 feet, use 3/4". Over 50 feet, use 1". Always verify total load on the line.
Can I use CSST flex gas line?
Yes, CSST is code-approved in most jurisdictions. It must be bonded per manufacturer specs. Size per the manufacturer's tables, which differ from rigid pipe tables.

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