TIG Welding Argon Flow Calculator

What this page is for

This page helps you choose a starting shielding gas flow rate for TIG welding, especially for stainless exhaust and header fabrication. It is meant to give you a reliable starting point so you are not guessing every time you change cup size, gas lens setup, or material.

In simple terms, this is the page for figuring out, “How much argon should I be running through the torch?” That matters because too little gas can let contamination in, while too much gas can create turbulence and make shielding worse instead of better.

Why argon flow matters

Shielding gas protects the weld puddle, tungsten, and hot weld area from oxygen and contamination. If gas coverage is weak, stainless colors badly and weld quality drops.

But more gas is not always better. Several welding references point out that excessive flow can create turbulence, which can actually pull surrounding air into the shielding stream and hurt the weld.

The simple rule-of-thumb formula

A very common starting rule is:

A slightly broader shop rule is:

That means:

• #5 cup → about 10 CFH.

• #6 cup → about 12 CFH.

• #7 cup → about 14 CFH.

• #10 cup → about 20 to 30 CFH depending on setup and conditions.

What the inputs mean

• Cup size: the TIG cup number, usually based on sixteenths of an inch.

• CFH: cubic feet per hour, the most common gas flow unit on US flowmeters.

• Gas lens or standard collet body: gas lenses generally give smoother, more laminar gas flow and often let you run more efficiently than standard setups.

• Stickout: how far the tungsten extends past the cup. More stickout usually needs more shielding support.

• Shop draft: fans, open doors, and moving air can force you to raise flow.

How to calculate it

1. Start with your cup number.

2. Multiply by 2 for a solid first setting in CFH.

3. If you are using a larger cup, more stickout, higher amperage, or welding in a drafty area, move toward the 2.5 to 3 times range.

4. Fine-tune based on actual shielding quality, tungsten behavior, and weld color.

Worked example 1

Let’s say you are welding stainless with a #6 cup and a fairly normal setup.

That gives a starting point of about 12 CFH, which fits very well within common TIG recommendations.

Worked example 2

Now say you are running a #10 cup on stainless with a gas lens and more stickout.

Using the broader shop rule:

That means a realistic starting range is about 20 to 30 CFH, which lines up with practical welding advice for larger cups.

Worked example 3

If you are welding stainless tube with a #8 cup in a calm shop and moderate amperage, a midpoint rule can work well:

That gives a good starting target of around 20 CFH, especially if you are using a gas lens and want solid coverage around the weld puddle.

Cup size chart

Here is a practical way to think about it:

Material-specific guidance

Many general TIG references say typical argon flow is often around 15 to 20 CFH for everyday work. Stainless TIG welding commonly falls in roughly the 10 to 20 CFH range, while titanium runs higher, around 17 to 25 CFH in many setups.

That matters because a stainless header shop is usually working in the part of the range where cup size, gas lens, and weld position make a bigger difference than just copying one “default” number every time.

High amperage and special conditions

One detailed reference notes that when current goes above 200 amps, convection around the weld area increases and shielding gas flow often needs to be raised by around 15 to 25 percent to maintain protection.

Helium mixes can also require significantly more flow than straight argon, sometimes around 1.5 to 2 times higher, because helium is lighter and behaves differently.

Purge gas for stainless tube

If you are welding stainless exhaust or header tubing, torch gas is only half the story. Root purge is also important, and one source gives a typical stainless purge flow range of about 6 to 10 CFH. This can vary dramatically based on the volume of the tube or area being purged.

For reference, when purging a 2 1/4" diameter header tube at 32" in length, we typically start with a higher purge rate of 15-20 CFH for 30-60 seconds to bolster the airflow, then lower it back to about 10CFH during the welding process, enough to continue moving gas through the tube and maintaining a positive pressure internally to prevent any atmospheric air or oxygen from penetrating into the tube and disturbing your weld area.

How to think about the result

If the weld is sugaring, turning ugly colors, or the tungsten is getting contaminated, the answer might be more gas — but it might also be less gas if the flow is too high and becoming turbulent. That is why starting with a sensible calculated value is better than just cranking the regulator up.

A calm, controlled shielding envelope is the goal. You want enough gas to protect the weld, but not so much that the gas stream becomes unstable.

What this formula does not know

This calculator gives a strong starting point, but it does not directly know your tungsten stickout, torch angle, gas lens quality, cup shape, joint shape, shop airflow, or whether you are welding outside. Those things all affect the final setting.

That is why the cup-size rule should be treated as a baseline, not a law. Final adjustment should always be based on actual weld results.

Plain-English takeaway

If you want the short version: start around 2 times cup size in CFH, move upward if the cup is large or the setup is demanding, and avoid the mistake of thinking more gas is always better. For stainless exhaust work, stable shielding and good purge practice matter just as much as torch technique.