Welding Cable Size Calculator
Estimate welding lead size from amperage, one-way cable length, duty cycle, voltage drop limit, conductor metal, insulation rating, and ambient temperature.
Welding Lead Recommendation
| Cable Size | Area mm2 | 90°C Copper | 105°C Copper | 90°C Aluminum |
|---|---|---|---|---|
| 6 AWG | 13.3 | 150 A | 170 A | 92 A |
| 4 AWG | 21.2 | 195 A | 220 A | 121 A |
| 2 AWG | 33.6 | 260 A | 300 A | 161 A |
| 1/0 AWG | 53.5 | 360 A | 425 A | 223 A |
| 2/0 AWG | 67.4 | 420 A | 500 A | 260 A |
| 4/0 AWG | 107.2 | 600 A | 700 A | 372 A |
| 350 kcmil | 177.3 | 850 A | 990 A | 527 A |
| 500 kcmil | 253.4 | 1050 A | 1225 A | 651 A |
| Drop Target | Arc Feel | Best Use | Typical Action |
|---|---|---|---|
| 2% | Tight | Precision TIG | Upsize early |
| 3% | Stable | Shop MIG or stick | Good default |
| 4% | Soft | Long field leads | Check arc starts |
| 5% | Loose | Rough repair work | Avoid if possible |
| Input | Light Load | Normal Load | Heavy Load | What Changes |
|---|---|---|---|---|
| Duty cycle | 20% to 30% | 40% to 60% | 80% to 100% | Heat allowance |
| Ambient | 30°C or less | 31°C to 40°C | 41°C to 50°C | Ampacity derate |
| Insulation | 60°C | 75°C to 90°C | 105°C | Allowable heat |
| Parallel leads | 1 lead | 2 leads | 3 leads | Current split |
| Setup | Amps | One-Way Length | Common Cable | Notes |
|---|---|---|---|---|
| Small MIG cart | 140 to 180 A | 25 to 50 ft | 4 to 2 AWG | Short shop lead |
| Stick welder | 200 to 250 A | 50 to 100 ft | 1 to 2/0 AWG | Watch drop |
| Mobile repair | 250 to 350 A | 100 to 150 ft | 2/0 to 4/0 | Long circuit |
| Air arc | 400 to 600 A | 50 to 100 ft | 4/0 to 500 | High current |
There is a balance between heat and voltage drop when it comes to sizing your welding leads. The amperage rating on your machine isn’t the only consideration when sizing welding lead. Also, you have to think about how far current has to travel. It travels from machine to work piece and then back again.
That’s called the round trip and there is resistance along the way. The resistance produces a voltage drop which reduce the strength of the arc. It also produce heat that can burns through the insulation of your cables from the inside out.
How to Choose the Right Welding Cable Size
That all gets put together in a recommendation from the calculator which makes it easy. All you need to do is input distance in feet from water source to your one electrode. The tool then doubles that distance to represent return path of the ground. Why does that matter? Because ground cable is just as vital as electrode lead. Running a 100 foot cable means the whole electrical pathway are 200 feet. The tool accounts for that, you don’t necessarily have to remember it when you’re carrying around the gear.
Cable requirements is also tied into duty cycle. For example, a fabricator who use a MIG welder for several hours is not in the same boat as a hobbyist who uses it for short periods of time. Silent danger exist from continuous heat build up in the cable jacket. This will soften the rubber causing the cable to become brittle and stiff. Cracking will occur and ultimate cause failure. The temperature rating of insulation indicates what amount of heat the jacket can withstand without damage. Thinner cables in hot conditions require higher ratings; however, these cost more.
Now we come to target voltage drop. Here’s where physics and your preference enter the picture. For example, a tight drop of 2 percent give you a nice crisp arc that responds well to your hand movements. It is great for welding thin sheet metal or doing precision TIG work. On the other end of the spectrum, you can get away with a loose drop of 4 or 5 percent if you’re welding heavy structural steel. But then the arc won’t respond as crisply and it feels sluggish. Refer to table on the page that shows how various percentage drops affect the arc feel. What kind of arc do you want?
The other variable is type of material. Standard material is copper because it is small enough to fit into flexible jackets and is a good conductor of electricity. Aluminum is less expensive and lighter, but you need larger diameters to handle same amount of electricity. If weight matter more than price, aluminum might be a good option. You should of remembered that you can’t use the same size as copper. The calculator accounts for that automatically. It will give you proper cross-section area based off your chosen metal.
Don’t let the cord get in the way. Don’t worry about lead resistance; instead, focus on weld puddle. The tools becomes an extension of your hand if heat remains in a safe range and voltage reaches the tip with enough force. Properly sized cables create a steady, clean arc. The key lies in choosing proper cable before starting to weld.
