Gas Line Size Planning Guide
Safe Flow Starts With Load
A gas line must carry the appliance demand without starving burners. The first input is total heat load. Add each burner, heater, dryer, generator, or boiler rating. The calculator converts that load into gas flow using the heating value. Natural gas often uses about one thousand BTU per cubic foot. Propane usually carries more heat per cubic foot. Your local supplier value is better than any default.
Length Matters
Pipe length is more than the straight run. Fittings, valves, risers, and flexible connectors add resistance. This page lets you enter equivalent fitting length separately. The calculator then uses total effective length. A longer path needs a larger internal diameter. A larger diameter reduces velocity and friction. It also improves pressure stability when several appliances start together.
Pressure Drop Control
Every gas system loses pressure while gas moves. The allowed drop should match the appliance and local code design. Low pressure systems often use a small drop allowance. Medium pressure systems may use regulators near appliances. The calculator estimates friction loss using flow, density, roughness, and diameter. It also checks velocity against your selected limit. This gives a practical engineering estimate before final code review.
Material And Safety Margin
Different pipe materials have different internal sizes and roughness. Steel, copper, plastic, and corrugated stainless tubing can behave differently. The nominal size table helps convert a calculated inside diameter into a purchasable size. The safety factor increases required capacity before sizing. Use it when future appliances may be added. Use it when the layout is uncertain.
Practical Use
This calculator is useful for early planning, quotes, and comparisons. It does not replace licensed design. Gas work can be hazardous. Local tables, pressure tests, permits, and inspection rules may control the final answer. Always confirm appliance inlet pressure, regulator settings, elevation limits, and approved material. Keep records of inputs and results. Export the CSV or PDF report for review. Share it with the installer before buying material.
Common Design Review Checks
Check demand diversity only when a code method allows it. Check pipe labels, burial rating, bonding rules, and shutoff access. Recalculate after route changes. Small changes can create larger pressure losses later.