Gas Line Sizing Calculator

1. Select gas type. Natural gas and propane have different energy densities and code tables. Propane delivers roughly twice the BTU per cubic foot, so pipe sizes can be smaller.

2. Enter total BTU load. Add up the nameplate BTU input rating for every appliance on the pipe run. Use the reference table below the inputs for common appliance ratings.

3. Enter pipe length. Measure from the gas meter to the farthest appliance on the run. This is the longest pipe path, which determines the sizing for the entire main.

4. Review the recommendation. The calculator provides minimum pipe size per IFGC tables, plus the pipe's capacity and safety margin at that size.

Gas line sizing uses capacity tables from the International Fuel Gas Code (IFGC), specifically Table 402.4 for Schedule 40 iron pipe at standard inlet pressures.

The tables account for pressure drop over the pipe length. Longer runs require larger pipe to maintain adequate pressure at the appliance. The safety factor shows how much headroom you have for future appliance additions.

Adding a new gas appliance. Before installing a tankless water heater, gas range, or other appliance, verify the existing gas line is large enough to handle the additional BTU load.

New construction gas piping design. Size the main from the meter and each branch to individual appliances. Start with the total load at the meter and size branches individually.

Troubleshooting low flame or appliance error codes. If a gas appliance won't fire at full capacity or throws error codes, the gas line may be undersized. Calculate the required size and compare to what's installed.