What Size Welding Gas Cylinder for MIG or TIG? Argon|CO2

If you’re new to MIG or TIG welding, you may have no idea how much welding you’ll do—let alone how much welding gas you’ll go through.

But you’d probably like to have some sense of how long a welding gas bottle will last before deciding what size cylinder to choose.

I’ll show you how much welding time to expect from the most popular cylinder sizes used by hobbyists. Then you can compare physical dimensions so the bottle will fit your vehicle or welding cart. 

You’re only a quick read away from knowing what size welding gas cylinder to choose.

Welding gas bottles.

Popular Welding Gas Bottle Sizes for MIG and TIG

You’ll find them smaller and larger, but most homeowner and hobby welders choose Argon or MIG mixes in gas cylinders with volumes of 40, 80 or 125 cf (cubic feet).

The larger of these cylinders provide plenty of welding time while remaining portable and easy to transport.

Keep in mind that specifications may vary among cylinder manufacturers. And because you may see high-pressure bottles labeled by a letter or content weight, I’ve included commonly used alternatives.

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Welding Gas Cylinder Specifications (Argon/MIG Blends)

Size40cf (V)80cf (Q)125cf (D)
Height22 in35 in45 in
Diam.7 in7 in7 in
Empty24 lbs47 lbs58 lbs
Full Wt.28 lbs56 lbs71 lbs
PSI201520152265

While much larger cylinders are available, those are often leased bottles delivered to high-volume customers by the gas supplier.

The larger the cylinder, the more economical the refills. You won’t pay much more to get twice the gas.

My last purchase of an 80cf cylinder from a “local” supplier 20 miles from my home took about an hour and a half of my time.

At the time, I thought all the cylinders for sale online were empty.

Wrong!

I learned that I can order a full 80cf cylinder delivered to my door at a great price. These bottles get good, legitimate reviews that receive an “A” rating from Fakespot. 

Any decent gas supplier won’t have a problem refilling a good quality cylinder, but you’ll want to check your local options.

You may find a small, but helpful, gas supplier like the one in this video. See the cylinders popular with hobbyists, along with what to look for when buying used gas cylinders. 

Related: MIG Welding with 100% Argon Shielding Gas

How long will welding gas last?

How much welding time you’ll get per bottle will depend on the flow rate you’ll set on your regulator—usually between 10 to 40 cfh depending on the work environment.

You’ll need a higher flow rate to maintain shielding gas protection in a windy area. Even with my garage door open 12 inches, I get good results with a regulator setting of 20 cfh as long as it’s calm.

Since we’re dealing only in cubic feet, our welding-time calculation for gas cylinders is simple:

Gas welding time (hours) = (cylinder volume in cf) / (regulator flow rate in cfh)

So, using my 80cf cylinder, regulated at 20 cfh: (80 cf) / (20 cfh) = 4.0 hours of welding time.

Welding time per cylinder by gas flow rate (Argon/MIG blends)

Size40 cf80 cf125 cf
10 cfh4.0 hrs8.0 hrs12.5 hrs
15 cfh2.7 hrs5.3 hrs8.3 hrs
20 cfh2.0 hrs4.0 hrs6.3 hrs
30 cfh1.3 hrs2.7 hrs4.2 hrs
40 cfh1.0 hrs2.0 hrs3.1 hrs

Of course, these are calculated times and your real-life welding results will vary. Significant temperature swings and the frequency of start and stops—especially with machines having pre/post-flow settings—will affect your run time. 

More about pre/post flow: Features of Advanced MIG Welders under $1500

It’s a good practice to check your regulator occasionally as you weld. As the gas is used up, cylinder pressure drops changing the flow rate from single-stage regulators. Again, temperature changes have the same effect, so don’t be surprised if you’re adjusting the regulator more often than you expected.

I’ve picked up the habit of backing out the gas regulator adjustment to “0” when I finish a welding session. Recommended by manufacturers to remove spring pressure from the valve diaphragm, this practice also forces me to adjust gas flow the next time I weld.

Photo of MIG gas regulator gauge set.

What about 100% CO2 gas cylinders?

100% CO2 gas cylinders used for MIG welding are different than Argon and MIG blends. CO2 tanks use different valves and are filled by weight instead of volume. One pound of CO2 provides 8.741 cf of shielding gas.

100% CO2 (C100) Cylinder Sizes and Operating Time

SIZEH x W (in)CU FTTIME*
1.25#10.5 x 310.933 min
5#18.25 x 5.543.72.2 hrs
10#20.5 x 787.44.4 hrs
20#27.5 x 8174.88.8 hrs
50#47 x 8437.121.9 hrs
*Approximate welding time at 20 cfh flow rate

Read all about: MIG Welding with 100% CO2 Shielding Gas

How much gas is left in the cylinder?

With a full welding gas cylinder at 70 degrees, the pressure gauge should read near the cylinder’s working pressure. Barring a drastic temperature change or a leak, you can expect the pressure to respond linearly to the remaining gas volume.

So, if your full cylinder started with 2000 psi on the pressure gauge, a reading of 1000 psi tells you that roughly 50% of your gas remains.

Some pressure gauges are more accurate than others, especially in the lower range. But as long as the regulator is maintaining the set flow—while the trigger is pulled—you can keep on welding, knowing that your weld is protected.

Don’t be concerned if you notice the gauge seems to hold steady for a time, then drops suddenly. The slow gas discharge rate that we use in welding can cause the pressure dial to hang-up temporarily. It won’t take long before you get a feel for the accuracy of your pressure gauge.

See why MIG is the Best Welder for Beginners.

Photo showing the size of a 20 cu. ft. MIG gas cylinder next to a 140 amp MIG welder.

How much MIG wire will I use?

If you’re at all like me, now that you know how long the MIG gas will last, you’d like to know how much wire you’ll use per cylinder.

Here’s how to get that with a deposition rate (lbs/hr) formula.

Welding wire deposition rate formula

13.1 (D²)(WFS)(EE) where: 

  • D = electrode diameter
  • WFS = wire feed speed (inches per minute)
  • EE = electrode efficiency
  • 13.1 = is a constant based upon the density of steel and its cross-sectional area.

If the melt-off rate is all that is required, then use the same formula without the EE factor.

I found this formula in the free guide Gas Metal Arc Welding | Product and Procedure Selection by Lincoln Electric.

Because we’re interested in how much wire we’ll use—not how much makes it into the weld—we don’t need to use an efficiency factor.

Let’s see what happens if we use .030” solid wire at 250 ipm:  

13.1 x (0.030)² x (250) = 2.95 pounds of wire per hour.

From our first table, I know that my 80cf cylinder should provide 4 hours of welding when regulated to 20cfh. This means I should expect to use around 12 lbs. of 0.030” wire per cylinder when welding at 250 ipm.

We can reduce the constant and wire size in this formula to a simple factor providing MIG wire use per hour with different wire sizes and wire feed speeds.

Calculate MIG wire use per hour using wire diameter and wire feed speed (ipm):

  • 0.025″ wire:  0.008 x (WFS)
  • 0.030″ wire:  0.012 x (WFS)
  • 0.035″ wire:  0.017 x (WFS)
  • 0.045″ wire:  0.027 x (WFS)

Example using 0.030″ wire: (0.012) x (250 ipm) = 3.0 lbs/hr

Conclusion

You’ve seen how long MIG gas will last, and how much welding time you can expect from bottle. I hope you now have a good idea what size welding gas cylinder is right for you—so you can start MIG welding soon!

But if you still have questions, leave a comment below and we’ll get it answered for you.

Dave Jones
 

Dave began welding to repair equipment used in his small business. Now as a hobby, he enjoys researching, testing and writing on welding topics. Other interests include photography, RVing and just about anything to do with dogs—especially retrievers.