Welding and Metalwork Calculators
Shielding gas cylinder duration.
Enter the flow rate from your flowmeter and pick a cylinder (or type its contents) to see how many hours of gas flow you get. Add a price for cost per hour. Runs in your browser; nothing is sent or stored.
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Result
Fill the form and press Calculate.
Answer first. Cylinder life = usable gas in cubic feet / flow in cfh. A size 125 argon cylinder holds about 126 ft3, so at 25 cfh it gives about 5.0 hours of gas flow (126 / 25 = 5.04). At 12 L/min (25.4 cfh) it is almost the same.
Worked example
A size 60 argon cylinder (about 56 ft3) at 20 cfh runs for 56 / 20 = 2.8 hours. If gas flows for 3 minutes per weld that is 1 ft3 per weld and about 56 welds. At a $60 fill the gas costs about $21 per flow-hour.
How it works
Cylinder contents. The presets are the approximate pure argon figures on Airgas product pages: size 60 about 56 ft3, size 125 about 126 ft3, size 150 about 155 ft3 and size 300 about 336 ft3. Airgas notes the actual volume varies with conditions. Argon-CO2 mixes and other gases hold different amounts, so choose Other and type the figure from your cylinder label or supplier.
What flow to set. Miller Electric's guide for MIG on mild steel says to set the flow to 20 to 25 cubic feet per hour, and its gas article recommends 25 to 35 cfh for MIG short-circuit welding. TIG typically runs a lower flow rate. Miller says too low a flow introduces porosity, and too high wastes gas and can cause turbulence that draws in air. Follow your wire or machine datasheet, and adjust for drafts.
Usable share and arc-on share. Do not run a cylinder to empty. Lower the usable share if you change cylinders early. Gas flows from trigger pull through post-flow, not only while the arc is on, so the arc-on share turns flow hours into arc hours: 40 percent means 1.44 arc hours from 3.6 flow hours.
Safety. Welding produces arc radiation, fumes, sparks and burns. Use a proper welding helmet, gloves and flame-resistant clothing, ventilate or extract fumes, and remove flammables from the area. This is a planning aid, not a welding procedure, engineering design or professional advice.
Sources
- Industrial Grade Argon, Size 125 cylinder (Airgas); sizes 60, 150 and 300 on the same product family (opened 2026-10-15)
- Understanding the Basics of MIG Welding for Mild Steel (Miller Electric) (opened 2026-10-15)
- What Type of Gas Is Best for MIG Welding in DIY Applications (Miller Electric) (opened 2026-10-15)
1 cubic foot = 28.316846592 litres, so 1 L/min = 2.119 cfh.
FAQ
How long does a size 125 argon cylinder last?
About 126 ft3 divided by your flow: roughly 5 hours at 25 cfh, 6.3 hours at 20 cfh and 4.2 hours at 30 cfh of continuous gas flow.
What cfh should I set for MIG welding?
Miller says 20 to 25 cfh for MIG on mild steel and 25 to 35 cfh for short-circuit transfer. Check your wire datasheet and adjust for drafts.
What happens if the flow is too high or too low?
Miller says too low introduces porosity from poor puddle coverage, and too high wastes gas and can produce turbulence that pulls in air.
Does 100% argon and argon-CO2 mix use the same cylinder volume?
Not necessarily. The presets are pure argon figures from Airgas. For a mix, choose Other and enter the contents printed on the cylinder or supplier sheet.
How do I convert L/min to cfh?
Multiply by 2.119. For example 10 L/min is 21.2 cfh.