Gas Flow Rate Calculator

It's a widely used shop rule of thumb in MIG and TIG welding: recommended shielding gas flow in CFH is roughly twice the nozzle's inside diameter measured in sixteenths of an inch. It's a practical starting point developed from field experience rather than a first-principles physical derivation, which is why this calculator also reports a minimum-to-maximum working range around it rather than treating the baseline as an exact target.

A groove weld typically exposes a larger, deeper weld pool and heat-affected zone to the atmosphere than a simple fillet weld does, and any part of that hot metal left unshielded can pick up atmospheric nitrogen and oxygen, causing porosity. This calculator applies a modest flow increase for groove welds to help keep that larger exposed area covered.

Shielding gas is a low-velocity, low-density flow relative to open air, so even a mild breeze -- including an indoor draft from a shop fan or an open bay door -- can physically blow the gas shield away from the weld pool before it fully solidifies, causing porosity. In genuinely windy outdoor conditions, increasing flow alone often isn't enough, and using a physical windscreen around the weld area is usually more effective than flow rate alone.

Aluminum and stainless steel are more reactive with atmospheric oxygen and nitrogen during welding, and aluminum in particular is typically shielded with 100% argon (which is denser and behaves differently than the CO2-blended mixes common for carbon steel), so both benefit from a somewhat higher and more consistent flow to keep the weld pool fully covered through solidification.