How much shielding gas a weld burns through
Shielding gas is metered by flow rate and runs for as long as the arc is on, so the total used comes down to two numbers: how fast it flows and how long you weld. This calculator multiplies the two, then tells you how much of a cylinder that is and what it costs — handy for quoting and for knowing when the bottle is about to run dry.
The calculation
Gas used = flow rate x arc time. In imperial that is cubic feet per hour times hours, giving cubic feet. In metric it is litres per minute times minutes, giving litres. Only arc-on time counts, plus a small post-flow each time the trigger releases.
Typical flow rates
| Process / setup | Flow (CFH) |
|---|---|
| MIG, light gauge, no draft | 20 – 30 |
| MIG, general fabrication | 30 – 40 |
| TIG, most work | 15 – 25 |
| Outdoors or large nozzle | 40 – 60 |
More flow is not more protection — past a point it pulls air into the shield and causes porosity. Set it to the lowest flow that gives clean welds.
Where this fits
Get your arc time from the weld time calculator, then bring it here. To fold gas into a full job price alongside wire and labor, use the welding cost calculator.
Worked example
MIG at 35 CFH for one hour of arc time uses 35 cubic feet of gas. From a 251 cubic foot cylinder that is about 14 percent of the bottle, or roughly 8 dollars at 60 dollars a fill.
FAQ
Does flow rate depend on the cylinder size?
No. Flow rate is set at the regulator and is the same whether the bottle is large or small. Cylinder size only changes how many minutes of welding you get before a refill.
What about post-flow waste?
Each weld stop leaves a few seconds of post-flow, which adds up on lots of short tacks. For continuous welding it is negligible; for tacking, add a little to your estimate.