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

New MIG and TIG welders often have to guess how much welding they’ll do. That also means they don’t really know how much gas to plan for, which makes buying gas tanks way more confusing for a beginner.

Nobody wants to run out of gas every other day, but those huge tanks are heavy and hard to move or store. So, knowing how long different tank sizes last helps new welders pick the right size for their needs.

You can use some simple guidelines and calculations to estimate how long popular tank sizes will last. We’ve put that data together in this quick reference so beginners can choose a tank that fits their situation. Size and weight always matter, so we’ve also included the dimensions and weight of each tank. You’ll want to know if a certain gas tank can fit in your truck, welding cart, or shop.

Welding Gas Bottle Sizes for MIG and TIG?

There are lots of gas tank sizes for MIG/TIG welding out there. But most homeowners or hobby welders end up using the 40, 80, or 125 cubic foot (“cf”) tanks filled with Argon or a MIG gas mix (75% Argon, 25% CO₂).

The biggest of these three gives you plenty of welding time without being too hard to move. So, if you have the space and can afford it, go with the 125 cf tank. If not, pick the 40 or 80 cf tank based on your budget and how much room you’ve got.

Also think about refills. A bigger tank costs less per refill. Getting “twice” as much gas doesn’t cost twice as much. So again, always get the largest tank you can fit and afford.

One last thing: those really giant tanks you might have seen are usually leased. They’re for high-volume users and often need delivery from the gas supplier. They’re not an option unless you run a big shop that does a ton of welding.

Recommended Argon/CO2 MIG Bottle Sizes

All the popular tank sizes are about 7 inches across, so they take up the same floor space and fit the same holder or cart.

The 125 cf tank is taller and heavier, and it can push a light-duty welding cart past its limit. When a cart is overloaded, it can wobble and be hard to move safely around your shop.

Most people keep two tanks of their main gas so they never run out or have to refill before the tank is empty. You can use two tanks of the same size, or pair one big 125 cf tank with a small 40 cf tank for backup. The small tank also works as a portable option for quick jobs away from the shop.

Do not stress about picking the wrong size. Most gas shops will swap sizes and just charge you the price difference.

Welding Gas Cylinder Specifications (Argon/MIG Blends)

Compressed gas cylinders come in different sizes, and their specs can vary by manufacturer. You might see high-pressure tanks labeled with a letter, a number, or the weight of the gas inside, so I added those details to the chart.

*All weights and dimensions are approximate.

Small tanks that hold 20 cubic feet or less are not common for TIG or MIG welding. You usually see these in portable oxy-acetylene welding kits.

Larger cylinders over 125 cubic feet do exist, but very few people own them. Most users lease or rent these from the gas supplier. These huge tanks are hard to move, and if they fall, they can cause damage or injury. Because of that, suppliers usually deliver them to high-volume customers.

Bigger tanks give you more gas for a slightly higher price, so refills are more economical. But the savings on gas do not make up for the ongoing rental cost if you do not use much gas.

My last time buying an 80 cf cylinder from a local supplier 20 miles away took about an hour and a half and cost way more than it should have. I ended up “buying” a used tank that needed a new hydro-test in five years and had the gas company’s name stamped on the neck ring.

The fine print on my receipt even said only that company could refill it. Back then, I did not know there was an easier way. I thought every cylinder sold online was empty.

A Better Way to Buy a Full Welding Tank

I later found out I could get these bottles delivered right to my door for a great price. They meet DOT safety standards and come hydro-tested. The company promises the tank will have at least eight years left on its hydro-test. Just don’t mix up the “2015” pressure stamp with the actual test date when you check.

Because they arrive with a blank neck ring, you can refill them at any supplier you choose. Most decent gas suppliers won’t have trouble refilling a good customer-owned cylinder. Some big companies don’t want to deal with small-volume users, so it’s smart to check your local options first.

I suggest finding a small, friendly gas supplier like the one in this video. He shows which cylinder sizes hobbyists use most and what to look for when buying gas cylinders.

How long will my tank of gas last?

If you’re just starting to weld, you’re probably wondering: “How long will my tank of gas last?” The answer depends on your flow rate, which is usually between 10 and 40 cubic feet per hour (cfh), depending on what you’re welding.

A higher flow rate helps keep the shielding gas steady, especially if it’s windy. Most welders find they need at least 20 cfh, even when there’s barely any wind. Also, the position matterswelding flat is easier than welding vertically, and that can affect how much gas you use.

To figure out how long a full tank will last, you can use this simple formula:

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

For example, if you have an 80 cf tank and you’re running at 20 cfh, your welding time would be: 80 cf / 20 cfh = 4 hours.

So, with those settings, your tank should last about four hours of actual welding.

Welding Time for Tank Sizes at Different Flow Rates

Just remember that your real-world numbers might shift a bit from the calculations because temperature changes and how often you start and stop affect the flow. This matters even more if you use pre-flow or post-flow settings.

Watch your regulator closely as you work. The pressure in the tank drops as you use the gas, which lowers the flow rate, so you’ll need to adjust it. Temperature swings can also change your flow, so expect to tweak the regulator more often than you think.

Try making it a habit to turn the gas regulator back to “0” when you’re done for the day. Manufacturers suggest releasing the pressure on the spring and valve diaphragm while the equipment is stored. Doing this also means you’ll reset and check your gas flow every time you weld again.

100% CO2 Gas Cylinders for MIG Welding

You can actually use pure CO2 to shield your MIG welds, even though it’s not the best choice for every situation. CO2 is just carbon dioxide the same gas that puts out fires and gives your soda or beer its fizz.

Most people choose CO2 for MIG welding because it costs less to run. There are some pros and cons, but we can save that chat for another time.

If you decide to go with a CO2 tank, there are two key things you need to know about sizing it.

• First, CO2 tanks aren’t measured by volume like other welding gas cylinders. Instead, the industry sizes them by weight.
• Second, the threads on CO2 tanks are different, so you’ll need a special regulator. You can’t just grab the one you use for Argon or your regular MIG gas mix.

Here are some common tank sizes you might want to think about.

CO2 Tank Specs and Use Time

How Much Gas Is Left in the Cylinder?

To keep your shop running, you need to know when you’re running low on gas. With Argon and Argon/CO₂ mixtures, you can use the pressure gauge on your regulator to estimate how much gas is left in the tank.

With 100% CO₂, the pressure drop isn’t as reliable because it falls suddenly near the end. To check a pure CO₂ tank accurately, you need to weigh it to see how much is inside.

When an Argon or Argon/CO₂ tank is full, the gauge should read near the maximum pressure, usually around 2015 psi. As you use the gas, the pressure drops.

For example, when you’ve used about a quarter of the tank, the gauge will show around 1500 psi. When it’s half full, it will read close to 1000 psi. The pressure keeps dropping as you use more gas.

Remember, as the pressure changes, you need to adjust your flow rate to keep a steady CFH. That means you should watch the gauges for more than one reason while you weld. Also, temperature changes can affect the tank pressure. If the temperature drops a lot, the pressure will drop too. Try to check your “full” reading at about the same temperature each time.

Regulator quality can vary, and sometimes the needle on your gauge might seem stuck. Don’t worry too much. The needle will usually start moving again if you wait a bit. You might see some sudden drops in pressure now and then, but that’s normal and nothing to worry about.