What Size TIG Welder Do I Need? Sizing Guide

Figuring out what size TIG welder do I need is one of the first roadblocks every new welder hits. It doesn’t help that manufacturer listings only give you a max amperage number with zero context. The truth is, the right size depends on three variables: your metal thickness, your power supply, and how long you weld continuously.

Get those wrong and you’ll either burn through thin steel or stall out on a 1/4-inch aluminum plate.

Our research across welder spec sheets, owner feedback, and American Welding Society guidelines shows the selection process is more predictable than most people think. Most duty cycles are measured over a 10-minute window, which makes that number easier to compare. As of 2026, the most common mistake isn’t buying too small.

It’s buying a machine without checking whether the shop’s electrical circuit can actually feed it. Let’s walk through the selection process step by step.

Why Getting the Size Wrong Costs You Time and Money

The wrong size doesn’t just disappoint. It costs real money. A 120V-only machine that can’t handle your aluminum project is a $600 paperweight.

A 250A machine you only use for thin stainless means you overpaid by $1,500 for features you’ll never touch. The cost mistake goes both ways.

Most first-time buyers focus on maximum amperage, but that’s only half the equation. Duty cycle and input power matter just as much. A 200A machine running at 180A with a 20% duty cycle will shut down after two minutes of continuous welding.

If you’re doing long runs on 1/4-inch plate, that’s frustrating. If you’re tacking together exhaust pipe, it’s rarely an issue.

There’s also the skill factor. TIG welding is a hand-eye coordination craft, and a machine matched to your work makes learning easier. Trying to weld 18-gauge sheet metal with a machine that only starts at 50A creates burn-through after burn-through.

We’ve seen more than one beginner quit because the equipment fought them at every step.

The real point is to buy only as much machine as your work demands, with a little room above that. That means choosing after you answer some questions, not before. If you’re still comparing processes, our breakdown of how the two processes compare will help clarify why TIG fits certain jobs.

The 30-Second Answer: Three Questions That Pick Your Welder Size

Here’s the fast answer. Ask yourself three questions.

• What material will you weld most? Steel and stainless need DC. Aluminum and magnesium need AC. If aluminum is in your future, buy an AC/DC machine.
• What’s the thickest material you’ll regularly weld? For steel, a good rule is about 1 amp per 0.001 inch. For aluminum, figure on roughly double that. If 1/8-inch aluminum is your norm, you need 180A minimum.
• What power does your shop have? A 120V outlet handles around 90 to 110 amps of TIG output. A 240V/50A outlet is what you want for any serious aluminum work.

Most home garages land on a 200A AC/DC inverter running off 240V. It covers 1/4-inch steel, stainless, and 1/8-inch aluminum, which is more capability than most hobbyists will ever use. If you only weld thin steel and stainless, a 150A DC-only machine on 120V could be enough.

If your work is mostly 1/4-inch aluminum, step up to 250A or find a shop with three-phase power.

This is the short answer, but it assumes you know your material thickness. That’s the next step.

What “Size” Really Means for a TIG Welder: Amperage, Duty Cycle, and Input Power

Welder size is a combination of three numbers, not one. Salespeople talk about max amperage, but the real spec sheet breaks down like this:

• Amperage range determines how thin and how thick you can weld. The low end matters for sheet metal. The high end matters for thick plate.
• Duty cycle tells you how long the machine can weld before it needs to cool down. It’s usually listed at a certain amperage, like 200A at 35%.
• Input power is the electricity the welder needs from the wall. More output amperage requires more input capacity.

A 200A welder with a low duty cycle isn’t a 200A welder for production work. It’s a 200A welder for short passes and a 100A welder for everything else. Before you compare brands, this is the most important thing to understand.

Minimum amperage is the hidden spec. A quality TIG machine starts around 5 to 10 amps. That’s what lets you fuse 0.030-inch sheet metal without blowing a hole in it.

Many cheaper welders bottom out at 20 or 30 amps, which limits thin work no matter how good your hands are.

Duty cycle is measured per the American Welding Society’s standard, usually as a percentage of a 10-minute period. A 200A welder at 30% duty cycle runs 3 minutes, then rests 7 minutes. Thermal protection kicks in automatically and stops output until the coils cool off.

That’s normal, but it’s also why serious welders pay extra for a 60% duty cycle.

TIG welding’s precise nature makes that minimum amperage and duty cycle even more important. You’re not laying down thick beads like MIG. You’re making controlled, small puddle welds, so the machine needs to respond smoothly at low settings.

Step 1: Identify Your Metal Type and Material Thickness

Everything starts with measuring your material. Use a caliper or a simple thickness gauge. Then classify the metal.

Steel and stainless run DC. Aluminum and magnesium run AC. If you’re welding multiple metals, your machine needs both modes.

Here’s a practical amperage chart based on typical recommendations from manufacturer spec sheets. Treat these as starting points, not hard rules.

Why does aluminum need so much more current? It conducts heat away fast. Steel glows and tells you where heat is building.

Aluminum just swallows it until suddenly the whole part melts. That’s why AC balance and a foot pedal are so valuable.

If your thickest regular job is 16-gauge mild steel, the low end of the chart matters most. You can get by with a 120V DC-only machine. But check the minimum amperage before buying.

A machine that starts at 30 amps will be rough on 18-gauge, which is exactly the kind of sheet metal work where TIG shines.

For thinner material, you’ll find more useful detail in our guide to sheet metal work. And if aluminum is your main material, our walkthrough on how to dial in aluminum covers the settings that matter.

Step 2: Check Your Power Supply Before Anything Else

Your wall outlet is the boss. A welder can have 300 amps on the spec sheet, but if your garage has one 120V/15A circuit, you’ll get a fraction of that before the breaker trips.

In North America, most homes have 120V circuits for lighting and standard outlets. A 120V/15A circuit can realistically deliver maybe 90 to 110 amps of TIG output once you account for the welder’s internal losses. That’s enough for thin steel and stainless, but not for aluminum plate.

For serious work, you want 240V. Most TIG welders designed for hobby and professional use are single-phase 240V units. A 240V/30A circuit powers a 200A machine comfortably.

A 240V/50A circuit handles 250A and above.

Here’s a simple reference:

Before you order a machine, verify the plug type. Many 200A welders use a NEMA 6-50 plug. Some dual-voltage machines come with a 120V plug and a separate pigtail or adapter.

If your dryer outlet is NEMA 14-30, you may need an adapter, and that adds cost and some risk.

Also check the breaker. A 240V/30A circuit needs 10 AWG wire. A 50A circuit needs 6 AWG.

If the wiring was installed for a stove or welder outlet, it’s probably fine. Don’t assume. Your local electrical code exists for a reason, and the welding safety rules from OSHA are there to keep you from being the one who finds out why.

If you’re brand new to the craft, our rundown of the basics of welding is a good primer before you start buying equipment. As of 2026, dual-voltage inverters are common in the 150A to 200A range. They let you run off a regular wall plug for small jobs, then plug into 240V when you need real power.

That’s the smart choice for most home welders who aren’t sure what’s waiting in the walls.

Step 3: Match the Amperage Range to Your Thickest Material

Once you know your power supply, match the machine to your thickest regular job. That chart from Step 1 is your guide. The goal is to buy a welder that sits comfortably in the middle of its range for that material, not one that maxes out every time you touch the torch.

For steel and stainless on DC, think of it as roughly 1 amp per 0.001 inch. A 1/8-inch plate needs around 125A. A 16-gauge sheet needs about 50A.

That rule holds across most of the chart, and it’s a solid planning number.

Aluminum on AC is a different animal. It needs nearly double the current because heat disappears into the material. A 1/8-inch aluminum plate wants 180A or more.

A 1/4-inch plate jumps to 250A. If aluminum is your primary metal, your minimum amperage matters less than your ceiling.

Here’s the practical decision rule:

• If your thickest regular job is under 1/8-inch steel or stainless, a 150A machine is plenty.
• If you touch 1/8-inch to 3/8-inch steel, or 1/8-inch aluminum, a 200A AC/DC machine is your sweet spot.
• If you weld 1/4-inch aluminum regularly, skip the 200A and go straight to 250A.

Buying bigger than the chart suggests doesn’t help. A 250A machine welding 16-gauge steel still needs to dial down to 40A, and its minimum output might not go low enough. That’s why the low-end amperage spec is just as important as the headline number.

If you plan to do fine automotive sheet metal work, check that minimum first. For more on how different metals behave under the torch, our reference on the best technique for steel covers the practical side of amp selection.

Step 4: Square Up Duty Cycle With How You Actually Weld

Duty cycle is the spec that trips up first-time buyers. It’s the percentage of a 10-minute window a welder can run at a given amperage before overheating. A 200A machine at 35% duty welds for 3.5 minutes, then needs 6.5 minutes of cool-down.

That’s normal. Every inverter welder has thermal protection that shuts it down when the internals get too hot.

Here’s how to interpret the numbers. Hobby machines often land at 20 to 35% duty at maximum amperage. That’s fine for tacking, short passes, and projects where you stop to fit parts.

Professional units hit 60% at rated output, which suits production work and long continuous weld runs.

Ask yourself how you weld. If you’re fabricating an exhaust system, you’ll make a weld, reposition, grind, and check fitment. Those breaks let the machine cool naturally.

A 20% duty cycle rarely bites you. If you’re welding a row of 3-inch beads on a railing nonstop, the machine will hit thermal shutdown exactly when you’re in the groove.

Air-cooled torches also have limits. A standard 17-series torch handles around 150A DC comfortably. A 26-series torch goes higher, around 200A.

For 250A AC on heavy aluminum, water-cooled torch setups are the difference between a comfortable weld and a torch that turns into a hand warmer.

The fix is simple. Multiply the duty cycle percentage by 6 minutes to get your continuous weld time. A 35% duty weld at 200A gives you about 3.5 minutes at full output.

Most home projects never need that. Production shops and auto fab reps do.

The TIG Welder Decision Tree: From Your Situation to Your Size

Here’s where everything comes together. Answer these questions honestly and you’ll land on the right size, no guesswork needed.

Path 1: The 120V DC-Only Path

You weld steel and stainless under 1/8 inch. You work in a garage that only has standard wall outlets. You don’t plan on aluminum welding anytime soon.

A 150A DC-only machine running on 120V is your match. It’s lightweight, affordable, and plugs into a regular outlet. You’ll live with limited duty cycle and you’ll never weld thick aluminum.

That trade-off buys a lot of capability for under $700.

Path 2: The 200A AC/DC Path

This is the home garage all-rounder. You weld steel and stainless up to 3/8 inch. You want to try aluminum sheet and plate up to 1/8 inch.

You have access to a 240V outlet or are willing to install one. A 200A AC/DC inverter with TIG and stick capability is your best bet. It handles most automotive repair, custom fabrication, and farm projects.

It’s also the most common size on the market, so your options stretch from budget units to serious pro-grade machines.

Path 3: The 250A+ Professional Path

You weld 1/4-inch aluminum as a regular job. You repair boat hulls, fabricate aluminum trailers, or take on production work. You have 240V/50A power or better.

Here, a 250A machine with a water-cooled torch and a 60% duty cycle pays for itself. You’ll spend $2,500 or more, but the arc stability and sustained output are worth every dollar when you’re welding for hours.

The decision tree works because it respects your actual situation. It also stops you from overspending on capability you’ll rarely touch. As of 2026, dual-voltage machines make Path 2 even more attractive.

They run off 120V for light work and 240V when you need the full amperage. If you’re unsure which path you’re on, that’s the safest bet. Aggregate buyer feedback confirms that skipping a size class above your needs only adds cost and rarely improves weld quality.

Mistakes That Cost New TIG Welders Hundreds of Dollars

The biggest mistake we see in the research is buying before checking the electrical panel. A 250A machine on a 120V circuit is like a sports car in a driveway with no road. Expect breaker trips and thermal shutdowns constantly.

Verify your outlet type, breaker rating, and wire gauge before you spend a cent.

The second mistake is ignoring the low-amperage range. A machine that starts at 30A feels coarse on 18-gauge steel. You’ll burn through more material than you weld.

Check that the minimum output is 5 to 10 amps before you buy if thin work is in your plans.

The third mistake is going DC-only when you think you might weld aluminum later. Upgrading a TIG machine means upgrading the whole machine. You can’t add AC to a DC welder.

Leaving a future aluminum project on the table saves you money now, but costs it later.

The fourth mistake is matching your welder to your most ambitious project instead of your most common one. That one-time 1/4-inch aluminum repair job doesn’t justify a 280A machine if you spend most weekends welding 1/8-inch steel. Oversizing hurts your budget and often hurts your low-end control.

The last mistake is forgetting the torch. A 200A machine with a cheap 17-series air-cooled torch will still run hot, even if the machine itself is fine. Factor in a quality torch upgrade or a water-cooled setup in your initial budget.

Real-World Price Anchors by Amperage Class

Prices shift yearly, but the 2026 market has clear bands. These are typical ranges for new machines with a basic torch and regulator included.

Remember that consumables add up. You’ll need tungsten electrodes, filler rods, and a 100% argon bottle. Argon is a rental expense if you lease a cylinder, or a one-time cost plus refill charges if you own it.

A full 80-cubic-foot cylinder runs around $60 to $80 to refill, depending on your area.

A good practice is to spend at least half your budget on the welder itself and reserve the rest for accessories. A mid-tier 200A machine with a quality foot pedal and gas lens beats a top-tier machine you can’t afford to torch properly.

One more cost factor: future-proofing. The 200A AC/DC class holds its resale value better than entry-level 120V units. If you outgrow it, you’ll recover more of your investment.

That makes it the smart financial choice for most home welders.

AC/DC vs DC-Only, Inverter vs Transformer, New vs Used

The first fork is simple. DC-only machines handle steel, stainless, and titanium. AC/DC machines add aluminum and magnesium to that list.

If you see aluminum in your future, the choice is already made.

The second fork is inverter versus transformer. Inverters are lighter, more efficient, and give you better arc control. Transformers are heavy, tough, and cheap, but their AC balance is usually fixed.

As of 2026, almost every new TIG welder sold is an inverter, so this comparison mainly matters if you're shopping used.

New machines come with a warranty, current safety certifications, and modern features like pulse and adjustable AC frequency. Used machines save money but bring risk: check the torch condition, inspect the power cord, and test the duty cycle behavior if you can.

Electrical Circuit Safety: What You Need Before You Plug In

Before you plug in, know your circuit. The National Electrical Code (NFPA 70) sets the rules for outlet types, breaker sizes, and wire gauge. A 240V/50A circuit needs 6 AWG wire.

A 240V/30A circuit needs 10 AWG. Don't guess, an electrician visit is cheaper than a fire.

Welders draw serious current, so use the right plug and receptacle. NEMA 6-50 is common for 240V welders. Some machines come with a 120V plug for light work.

Adapters exist, but they can overheat if the circuit isn't sized correctly. OSHA's welding safety guidance reinforces the same point: verify the supply before you strike an arc.

FAQs: "Can I Weld Aluminum With a 150A?" and Other Size Questions

Can I weld aluminum with a 150A TIG welder?

Yes, but only thin material. A 150A AC machine handles aluminum up to about 1/8 inch in practice. You'll need short weld passes and you'll want a foot pedal to control heat.

Thicker aluminum will stall the arc and melt the tungsten before it melts the joint.

Is a 200A TIG welder enough for a home garage?

For most home garages, yes. A 200A AC/DC machine with dual voltage covers steel, stainless, and aluminum up to 1/8 inch. It runs on 240V for full output or 120V for light duty.

That matches the needs of most hobby fabricators and repair work.

Does bigger amperage mean better welds?

No. Bigger amperage only means a higher ceiling. Small, precise welds actually get harder on oversized machines because the low-end control is often coarser.

Choose a machine that peaks near your regular work, not one that dwarfs it.

What's the difference between 200A and 250A for aluminum?

About 1/16 inch of practical thickness. A 200A machine reliably welds 1/8-inch aluminum. A 250A machine handles 3/16-inch and does 1/4-inch with careful technique.

The 250A also runs a 60% duty cycle, so it sustains longer weld passes without overheating.

Should I buy a used TIG welder to save money?

Used can be smart if you stick to reputable brands and test it first. Check for arc start issues, listen for grinding noises, and inspect the torch. If the seller can't demo it, walk away.

A new inverter welder under warranty is often worth the $200 price difference.

Final Verdict: The Right TIG Welder Size for Your Exact Situation

You need a 150A machine if your world is thin steel and stainless on standard outlets. You need a 200A AC/DC inverter if you want the versatile all-around garage machine. You need 250A or more if thick aluminum and continuous production runs are your reality.

Match the machine to your thickest regular material, not your most ambitious project. Check your electrical panel before you order. Leave room in the budget for a quality torch, gas lens, and argon cylinder.

In our research, nearly every disappointed buyer missed one of those three steps. Get them right and the welding part gets much easier. And if you're still deciding between processes, our comparison of TIG versus MIG will help you confirm the right approach before you commit.