How do I convert BTU/h to SCFH for a regulator?

Divide the total connected BTU/h load by the gas heating value, about 1030 BTU per cubic foot for natural gas and 2516 for propane. A 250,000 BTU/h natural gas load needs roughly 243 SCFH of flow capacity.

What is the difference between first-stage and second-stage regulators?

On a two-stage LP system the first-stage regulator drops high tank pressure to about 10 psi, and the second-stage regulator drops that to appliance pressure near 11 inches water column. Each stage is sized for the same flow but very different inlet pressures.

Why does inlet pressure affect regulator selection?

A regulator body is rated for a maximum inlet pressure and its flow capacity is published at a given inlet. Feeding a line regulator more than its rated inlet is unsafe, so the tool only offers families whose maximum inlet meets or exceeds your supply pressure.

What if no regulator covers my load?

If the calculated SCFH exceeds every bundled family at your inlet pressure, step up to a larger regulator body and pipe size, raise the system pressure with a two-stage layout, or split the load across multiple regulators feeding separate branches.

Are the bundled capacities exact?

They are representative of common residential and light-commercial regulator families and are meant for first-pass selection. Always confirm the final choice against the manufacturer published capacity table for your exact inlet-to-outlet pressure drop.

Gas Pressure Regulator Sizing Calculator

A gas regulator must pass the full connected appliance load in cubic feet per hour while holding the right outlet pressure, so sizing starts by turning BTU/h into SCFH and then matching that flow to a regulator rated for your inlet pressure. This calculator does both and recommends a regulator family.

How it works

The connected load converts to volumetric flow through the gas heating value, then a regulator is chosen from bundled capacity families:

SCFH = total BTU/h ÷ heating value
       (natural gas ≈ 1030 BTU/ft³, propane ≈ 2516 BTU/ft³)

The tool filters its bundled regulator families to those matching your gas type and stage whose maximum inlet pressure meets your supply, then picks the smallest whose rated capacity is at least the required SCFH. Families that fall short are still listed so you can see how much headroom each option leaves.

Example and tips

A home with 250,000 BTU/h of connected natural gas appliances needs about 243 SCFH. Fed at a 2 psi service pressure, a 3/4 inch line regulator covers it comfortably, while a 1/2 inch line regulator would be marginal as the load grows. On propane, the same load is only about 99 SCFH because propane carries far more energy per cubic foot. Always confirm the final regulator against the manufacturer capacity table at your real inlet-to-outlet pressure drop, and add a safety margin for future appliance additions.