TIG Welding Amperage Chart: Settings by Material Thickness

Dial in the wrong amperage on a TIG welder and everything else you do right stops mattering. Too little current and the puddle never fully forms, leaving a weld that looks fine on top and fails under load. Too much, and you're chasing a blown-out puddle across thin sheet metal, patching pinholes instead of running a clean bead. A reliable TIG welding amperage chart takes the guesswork out of that first, most important dial setting, so you can spend your attention on torch angle, filler feed, and travel speed instead of relearning amperage from scratch every time the material changes.

This guide breaks down amperage by material and thickness for mild steel, stainless steel, and aluminum, then layers in the settings that interact with amperage: tungsten size, shielding gas flow, AC balance, and pulse parameters. None of these numbers are absolute. They're a calibrated starting point that gets you within a few amps of a correct setting on the first pass, which is what every experienced welder is really working from anyway.

Why Amperage Is the Setting That Drives Everything Else

In gas tungsten arc welding (GTAW), amperage controls how much heat the arc delivers to the base metal per unit of time. That heat is what melts the parent material and the filler rod into a shared puddle, and the size, depth, and cleanliness of that puddle is what separates a structurally sound weld from a cosmetic one. Voltage in TIG welding is largely a byproduct of arc length rather than something you set directly, and travel speed is a technique variable you adjust in real time. Amperage is the one number you commit to before you ever strike an arc, which is why getting it close to right matters more here than in almost any other welding process.

TIG also gives you less margin for error than MIG or stick welding. There's no wire feed speed to compensate for a mismatched amperage, and the arc is smaller and more concentrated, so an amperage that's off by 20-30% shows up immediately as either lack of fusion or a collapsed puddle. That's exactly why so many welders keep a written chart on the wall next to the machine instead of relying on memory.

The Baseline Rule: 1 Amp per .001 Inch of Thickness

The starting point nearly every welder learns is simple: use roughly 1 amp for every 0.001 inch (one thousandth of an inch) of material thickness when welding mild steel with direct current electrode negative (DCEN). An eighth-inch plate (0.125 in) starts at around 125 amps. A sixteenth-inch sheet (0.0625 in) starts around 60-65 amps.

This rule is a genuinely useful heuristic, and it holds up reasonably well up to about 1/8 inch (0.125 in) of mild steel. Past that point it starts to break down, because thicker sections conduct heat away from the weld pool faster than the linear relationship accounts for, and the joint design (bevels, root gaps, multiple passes) starts to matter more than raw thickness. On material heavier than about 3/16 inch, most welders shift from a single-pass mentality to a multi-pass strategy with a bevel, and amperage is chosen per pass rather than as one number for the whole joint.

The rule also assumes mild steel. Aluminum's high thermal conductivity means heat escapes the weld zone far faster than in steel, so aluminum typically needs 30-50% more amperage than steel of the same thickness. Stainless steel behaves the opposite way: its lower thermal conductivity traps heat near the weld, so it typically runs about 10% less amperage than mild steel at the same thickness to avoid overheating, warping, and carbide precipitation in the heat-affected zone.

TIG Welding Amperage Chart by Material and Thickness

The table below gives practical starting ranges for square-groove butt joints in the flat position, using DCEN for steel and stainless, and AC for aluminum. Treat the low end of each range as your starting point on a foot pedal or amperage dial, then walk it up until the puddle forms cleanly without lagging behind the torch.

A few notes on reading this chart correctly:

• Below 1/16 inch, most welders lean on pulse TIG or a foot pedal more than a fixed dial setting, since the margin between "not fusing" and "blown through" is only a few amps wide.
• Above 1/4 inch, single-pass welding without a bevel becomes impractical. These ranges assume a prepared joint (V-groove or J-groove) and multiple passes, with amperage adjusted slightly lower for the root pass and higher for fill and cap passes.
• These are butt-joint numbers. Fillet welds — T-joints, lap joints, and corner joints — pull heat into two adjoining pieces of metal instead of one, so they typically need 10-15% more amperage than a butt joint on the same material and thickness to get full fusion into both members.
• Values assume a clean, properly fitted joint with minimal gap. A root gap or poor fit-up changes the effective heat sink and usually calls for adjusting a notch down from the chart to avoid burn-through.

What Else Changes Your Amperage Besides Thickness

Thickness sets the baseline, but several other variables shift the number meaningfully, and skipping them is the most common reason a "chart-correct" setting still produces a bad weld.

Joint configuration. As noted above, fillet and lap joints draw heat into more surrounding mass than a butt joint, so they run hotter. A corner joint on thin sheet, by contrast, has less surrounding mass to absorb heat and often needs less amperage than the chart suggests to avoid warping the flanges.

Position. Flat position welding tolerates the highest amperage because gravity works with you and the puddle stays where you put it. Vertical and overhead welds typically need 10-20% less current than the flat-position number for the same thickness, since a puddle that's too fluid will sag or drop out of position.

Material condition and alloy. Galvanized coatings, mill scale, oxidation, and oil residue all interfere with arc stability and can require a slight amperage adjustment along with proper cleaning. Different aluminum and stainless alloys also conduct heat differently — 5xxx-series aluminum, for instance, tends to need a bit more heat than 6xxx-series at the same thickness because of its alloying content.

Heat sink effects. Welding near a large mass of metal, a thick flange, or a heavy fixture pulls heat away faster than an isolated thin section would. The same 1/8-inch plate might need noticeably more amperage when it's welded to a much heavier piece than when it's joined to another 1/8-inch piece.

Preheat. On thicker carbon steel or on some stainless and aluminum alloys prone to cracking, preheating the joint reduces the amperage needed to reach fusion temperature and slows the cooling rate, which matters more for weld integrity than raw amperage does on heavy sections.

Tungsten Electrode Size and Amperage Capacity

Amperage and tungsten diameter are linked: too much current for a given electrode size causes the tip to ball, spit, or erode, while too little current on an oversized electrode makes arc starting difficult and produces a wandering, unstable arc.

For most sheet and light plate work in a home or fabrication shop, a 1/16-inch electrode covers the bulk of jobs from thin sheet up through roughly 1/8-inch steel, while 3/32-inch handles the mid-to-heavy range. Thoriated (2% or 1.5% lanthanated/ceriated as low-radioactivity alternatives) electrodes are typically used with DCEN on steel and stainless, while pure or zirconiated tungsten historically ran AC aluminum work — though modern inverters with AC balance control have made lanthanated and ceriated tungsten viable for aluminum too, with better arc starting and longer tip life than pure tungsten.

Shielding Gas Flow Rate by Thickness and Cup Size

Gas flow protects the weld pool from atmospheric contamination, but more isn't automatically better — too much flow creates turbulence that pulls in outside air just as effectively as too little flow leaves the puddle exposed.

A commonly used starting formula is cup number multiplied by roughly 2 to 3 to get CFH — a #5 cup runs around 10-15 CFH. Drafty shop conditions, welding near a fan or open bay door, or welding in a tight corner where gas can eddy back into the arc all push you toward the higher end of these ranges. Aluminum, with its wider, more turbulent AC arc cone, often runs 17-25 CFH even on thinner material to keep the larger puddle fully shielded.

AC Balance and Frequency for Aluminum

Aluminum forms a thin, hard oxide layer almost instantly on exposure to air, and that oxide melts at over 2,000°C (3,600°F) while the aluminum underneath melts around 660°C (1,220°F). AC current solves this mismatch by alternating between two phases: electrode negative (EN), which drives heat into the base metal for penetration, and electrode positive (EP), which breaks up the oxide layer in a cleaning action.

AC balance controls the ratio of EN to EP time. A common starting point is around 65-70% EN, which biases the cycle toward penetration while still cleaning enough oxide to keep the puddle bright and wetted out. Pushing balance further toward EN (75-80%) increases penetration and travel speed on thicker aluminum but can leave a dirty-looking puddle with a black oxide smear if taken too far. Pulling it toward more EP increases cleaning width — useful on aluminum with heavier oxidation or contamination — at the cost of penetration depth and tungsten life, since the EP phase heats the electrode more.

AC frequency, measured in hertz, controls how fast the machine switches between EN and EP. Lower frequencies (50-80 Hz) produce a wider, softer arc cone suited to thicker aluminum and wider fillets. Higher frequencies (120-250 Hz) focus the arc into a tighter cone, which improves directional control and is especially useful on thin aluminum sheet and detailed work where arc wander is a problem.

Pulse TIG Settings for Thin Material

Pulsing alternates the current between a high peak amperage and a lower background amperage at a set frequency, rather than holding one continuous value. This matters most on thin material and on materials that distort easily, because the average heat delivered to the part is lower than the peak amperage alone would suggest, while the peak still supplies enough energy to fully fuse the joint.

A practical starting point is to set peak amperage close to what a non-pulsed weld of that thickness would use, then set background current at roughly 25-40% of peak. On sheet metal under about 1/16 inch, pulse frequencies in the 1-5 Hz range let you see and control each individual pulse, which helps "walk the puddle" forward in a series of overlapping spot welds rather than one continuous molten track — a technique that dramatically reduces warping and burn-through risk on thin stainless and aluminum. Higher frequencies, from around 50 Hz upward, blur the individual pulses into what looks like a continuous arc while still delivering the metallurgical benefits of a lower average heat input, and are more common on thicker material where puddle control matters less than overall heat management.

Common Amperage Mistakes and How to Fix Them

Setting amperage too high for the joint, not just the thickness. A welder dials in the correct number for a butt joint, then runs a fillet at the same setting and gets undercut along the toe of the weld as the arc erodes the edge faster than filler can fill it back in. The fix is adding the 10-15% fillet allowance mentioned earlier, or simply watching the puddle and backing off the pedal the moment you see the edge starting to wash out.

Chasing a cold puddle by slowing down instead of turning up amperage. When the puddle isn't forming, the instinct is often to travel slower, but that just concentrates more total heat into a smaller area over a longer time and can lead to an oversized, overheated puddle without ever truly increasing fusion depth. If the puddle isn't wetting in within a normal travel speed, the amperage is usually the setting that needs to move, not the travel speed.

Ignoring the interaction between amperage and arc length. A longer arc spreads the same amperage over a wider area, effectively lowering the heat density at the puddle even though the machine's dial hasn't changed. Inconsistent arc length is one of the most common reasons a "correct" chart setting still produces an inconsistent bead — tightening up arc length control often fixes what looks like an amperage problem.

Using DC on aluminum or AC on steel. This isn't a fine-tuning issue but a fundamental setup error. Aluminum needs AC to break through its oxide layer; running it on DCEN produces a puddle that never cleans and looks contaminated no matter what amperage is used. Steel and stainless, conversely, are welded on DCEN — AC on steel wastes half the cycle on unnecessary cleaning action and reduces penetration for a given amperage.

Overcorrecting on a foot pedal. New TIG welders often ride the pedal aggressively, causing amperage to swing widely mid-weld. This shows up as a bead with inconsistent width and periodic dips or humps. Setting a slightly lower maximum amperage on the machine itself, so that full pedal travel can't overshoot the correct range, gives more room for smooth, gradual pedal control.

How to Dial In Your Settings in Practice

1. Start from the chart, not from memory. Pick the range for your material and thickness, and set the machine to the middle of that range as your first test.
2. Run a test bead on scrap of the same thickness and alloy. Production material is not the place to discover your amperage is 20 amps too hot.
3. Watch the puddle, not the dial. A correctly set puddle flows smoothly into a rounded, slightly concave shape and follows the torch without lagging or ballooning. If it's flat, sluggish, or the edges aren't melting in, add amperage. If it's collapsing, sagging, or blowing through, reduce it.
4. Adjust for joint type before adjusting for anything else. If the chart setting works on a butt joint test but the fillet weld looks undercut, add the fillet allowance rather than assuming the chart was wrong.
5. Lock in travel speed once amperage is right. Amperage and travel speed both control heat input, but changing them together makes it hard to tell which variable fixed or broke the weld. Get amperage right at a normal, steady travel speed first.
6. Record what worked. A shop notebook or a printed chart with your machine's actual dial numbers next to it saves far more time over months of welding than re-deriving settings from scratch every job.

Settings for Other Common TIG Materials

Chromoly and low-alloy steel are welded much like mild steel on DCEN, using the same amperage baseline, but because these alloys are more crack-sensitive, welders typically favor the lower end of the amperage range and pay closer attention to interpass temperature and post-weld cooling rate.

Titanium uses DCEN like steel but is far less forgiving of atmospheric contamination. Amperage settings track close to stainless steel figures, but titanium additionally requires a trailing gas shield and back-purge to protect the weld and heat-affected zone until they cool below roughly 800°F (427°C), since exposed hot titanium reacts readily with oxygen and nitrogen in the air.

Copper and copper alloys conduct heat even faster than aluminum, which pulls amperage requirements up significantly above steel at the same thickness, and often calls for helium or an argon-helium blend instead of pure argon to get enough heat into the joint. Preheating heavier copper sections is common practice, since copper's conductivity can make it nearly impossible to sustain a puddle on thick material without it.

Safety Considerations Tied to Amperage

Higher amperage means a brighter, more intense arc and correspondingly stronger ultraviolet and infrared radiation, which is why lens shade selection scales with amperage rather than staying fixed. Light-duty TIG work under roughly 100 amps is generally viewed under a shade 10-11 lens, while higher-amperage work on thicker material calls for shade 12-13 or higher to protect against arc flash and the corneal irritation known as "arc eye" or photokeratitis, which can result from just seconds of unprotected exposure. TIG's UV output is notably more intense than shielded metal arc welding at comparable amperage, which makes correct shade selection and full skin coverage — sleeves, collar, gloves — a non-negotiable part of setting up any TIG welding station, regardless of experience level. Adequate ventilation also matters more as amperage rises, since higher heat input vaporizes more base metal, coating, and filler material into airborne fume.

Getting Amperage Right Is the Foundation, Not the Finish Line

A good TIG welding amperage chart gets you into the right neighborhood fast, and that's genuinely valuable — it turns a blind guess into an informed starting point and cuts out most of the trial-and-error that frustrates new welders. But amperage never works in isolation. It interacts constantly with joint design, position, tungsten size, gas coverage, and your own travel speed and arc length control, and the welders who produce consistently clean welds are the ones who treat the chart as a starting point for the puddle to tell the rest of the story.

Print the ranges that match the work you actually do, run a test coupon before committing to production material, and adjust from there based on what the puddle shows you. That combination — a solid starting number plus attentive puddle reading — is what actually produces repeatable, strong TIG welds, far more than chasing an exact number down to the amp.