Welder Amp Output vs Input Power: What Matters

Output amperage: the number at the arc

On a welder listing, output amperage is the welding current the machine is stated to deliver at the arc. A title usually names a top figure, such as 85 amps, 160 amps or 205A, and often a range that names a low setting and a top figure. The top figure is what the machine can reach on its strongest setting; the range shows how low the controls can go for lighter work.

The stated output belongs to a process. A MIG welder, a TIG welder and a stick welder each use current in their own way, so comparing one machine's top amps to another machine's top amps is useful only when the process matches. Forney lists the 100 STx as a 120V stick and DC TIG welder that delivers up to 85 amps, and the 160 STx as a dual-voltage stick and DC TIG welder that delivers up to 160 amps. YesWelder lists the ARC-205DS PRO as a dual-voltage 205A stick and Lift TIG welder. Weldpro describes MIG as an arc welding process in which welding wire is the electrode and CO2 is the shielding gas, which is one example of how process words shape what an amp figure means.

The American Welding Society, which has defined more than 350 standards for the welding industry, is the organization behind the process names you see on titles. When an amp figure appears beside a process name, read it as that process's stated output, not as a universal number. If you are deciding how many amps a process needs, the learn article on MIG amperage answers that question in general terms: how many amps do I need for MIG welding.

Input power: the supply the machine draws

Input power is the supply a machine is built to draw, and a title names it in volts: 120V, 240V, dual voltage, or an industrial range such as 208-575 V. Miller lists the Multimatic 220 AC/DC with 120V or 240V input power, and the Multimatic 255 as a 208-575 V multiprocess welder. The input voltage is the supply, not the arc; the arc is measured by output amps.

Dual voltage is a common title word on machines meant for more than one place. Forney calls the 160 STx dual-voltage, and YesWelder calls the ARC-205DS PRO dual-voltage. A dual-voltage listing states that the machine accepts both common supplies, which matters when you plan to move the machine between places. The learn article on input voltage explains 120V versus 240V as a buying question: welder voltage input 120V vs 240V.

A title cannot show everything about the supply a machine needs. The maker's specification sheet names the supply it is built to draw, and an electrician can tell you whether the supply at your location matches the machine's input voltage. This site never states where a machine can be plugged in.

Output and input are separate figures

Output amperage and input power are two different numbers on a listing, and one does not predict the other. A machine with a high stated output may still be a 120V machine, and a 240V machine may have a modest top output. What matters for a buyer is the pair: the output range for the work you plan, and the input voltage for the place you plan to run it.

This site compares welders on stated details only and never maps output amps to a metal thickness. A thickness figure depends on the process, the joint, the material and the settings, none of which a listing states. The learn article on output amperage ranges explains how to read the range a title gives: welder output amperage range. The duty cycle is another rated figure you read alongside amps; the learn article on duty cycle explains the term in general terms: duty cycle explained for welders.

Reading output and input on a listing

When you read a listing, find the output range, usually named from a low setting to a top figure, and the input line: 120V, 240V, dual voltage, or an industrial range. If a listing names a top amp figure but omits the input voltage, the input voltage is a missing detail; ask the maker before buying. If a listing names both, compare the pair to other listings.

The same model can appear in several listings with different figures because sellers copy titles from different source pages or kits. Read the maker's specification sheet for the figures the maker states, and compare listings on those stated details rather than on headline numbers. The full welder guide on this site explains how picks are built from stated details: the full welder guide.

Matching both to your projects

For a first welder used for light work around the home, garage or farm, a 120V listing with a lower top output often pairs with the places you already have. For heavier or more frequent work, a 240V or dual-voltage listing gives a higher stated output. The guides on this site sort machines by these stated details: 120V machines in the 120V welder guide and dual-voltage machines in the dual voltage welder guide.

For a second machine, match the output to the process you are adding. A MIG listing, a TIG listing and a stick listing each state their own amp ranges, so compare within the process: the MIG welder guide and the stick welder guide each sort by process. If you want one machine for several processes, a multi-process listing combines them, but the input power and output are still two separate lines to read; the multi-process welder guide compares those machines on stated details.

When a higher output matters to you, the 200 amp welder guide lists machines that state a top output in that class, and you can read the input voltage line on each listing before you decide.

Questions to ask before you buy

Before you choose between output and input, ask the maker about the details a listing cannot show. These questions are a good start:

• What is the rated output range, and at which input voltage does the maker state it?
• Does the listing state 120V, 240V, dual voltage, or an industrial range such as 208-575 V?
• What does the maker's specification sheet say about the supply the machine is built to draw?
• If the machine is dual voltage, how does it switch between input voltages?
• What is the warranty period, and what does it cover? Everlast, for example, states a 5-year warranty on IGBT products and a 3-year warranty on MOSFET products.

What to pick for your situation

Questions

Is output amperage the same as input power?

No. Output amperage is the welding current a machine is stated to deliver at the arc, and input power is the supply it draws, named in volts such as 120V, 240V or dual voltage. A title usually lists both, and they are separate figures.

Does a higher output amperage mean a higher input voltage is required?

Not necessarily. A listing can state a modest top output on a 240V machine, and a 120V machine can state a lower top output. Read the pair on each listing instead of assuming one from the other.

What does dual voltage mean on a welder title?

A dual-voltage listing states that the machine accepts both 120V and 240V input. Forney calls the 160 STx dual-voltage, and YesWelder calls the ARC-205DS PRO dual-voltage. That matters when you plan to run the machine in more than one place.

Why does this site never map output amps to a metal thickness?

A thickness figure depends on the process, the joint, the material and the settings, none of which a listing states. This site compares welders on stated details and leaves thickness to the maker's manual.

What should I read before choosing an output and input?

Read the maker's specification sheet and manual for the rated output range and the input voltage it names, and ask the maker about anything the listing omits. The learn article on running watts explains the related power question: welder running watts.