Select a suitable copper welding cable size based on welding current, cable length, duty cycle and allowable voltage drop.
Welding cable must be large enough to carry the required welding current without excessive heating or voltage loss. Cable length is also important because resistance increases with conductor length.
This calculator checks two main factors:
The recommended cable is the smallest listed size that satisfies both conditions using the reference values built into the calculator.
For a normal welding circuit, the circuit resistance includes both the welding cable and the return cable.
Long welding cables have greater electrical resistance. This causes voltage drop between the welding machine and the workpiece.
The calculator therefore uses the complete circuit length when calculating voltage drop.
For example, a 10 metre welding lead paired with a 10 metre return lead creates approximately 20 metres of conductor in the complete circuit.
Welding cable current capacity varies according to conductor construction, insulation, ambient temperature, installation conditions and duty cycle.
The calculator uses approximate reference ampacities for flexible copper welding cable and applies a duty-cycle adjustment for estimation.
| Cable Size | Reference 100% Capacity | Typical Use Range |
|---|---|---|
| 10 mm² | 60 A | Light welding applications |
| 16 mm² | 80 A | Light to moderate current |
| 25 mm² | 110 A | Moderate welding current |
| 35 mm² | 135 A | Moderate to high current |
| 50 mm² | 170 A | Higher welding current |
| 70 mm² | 215 A | High current applications |
| 95 mm² | 260 A | High current / longer leads |
| 120 mm² | 300 A | High current applications |
| 150 mm² | 340 A | Very high current |
| 185 mm² | 385 A | Very high current |
| 240 mm² | 450 A | Heavy-duty welding |
Voltage drop is the reduction in voltage caused by resistance in the welding circuit.
The calculator uses copper conductor resistance values that decrease as cable cross-sectional area increases.
A larger cable therefore reduces resistance and voltage drop.
Keeping voltage drop within a reasonable limit helps maintain more consistent voltage at the welding arc, especially when using long leads and high welding currents.
Welding cables are often used intermittently rather than continuously. The duty cycle represents the proportion of a defined period during which welding current is flowing.
A cable that carries a particular current intermittently can have a different allowable current than when carrying that current continuously.
Higher duty cycles generally increase thermal loading, so cable selection should use the manufacturer's rating for the actual duty cycle and installation conditions.
Long welding leads can cause both voltage drop and additional heating. Increasing cable size can reduce resistance and improve voltage delivery at the workpiece.
When a welding machine is positioned far from the work area, increasing conductor size may be preferable to simply accepting a large voltage drop.
Cable connectors, electrode holders, work clamps and connection points also contribute resistance. Poor or undersized connections can create localized heating even when the main cable is adequately sized.
Flexible copper welding cable is commonly used because it combines good electrical conductivity with flexibility needed for moving welding equipment.
The actual cable construction matters. Two cables with the same nominal cross-sectional area can have different current ratings depending on insulation, conductor class, temperature rating and applicable standard.
For this reason, the result from this calculator should be treated as a preliminary selection rather than a substitute for the cable manufacturer's technical data.
What size welding cable do I need for 200 amps? The required size depends on cable length, duty cycle, installation conditions and allowable voltage drop. A short lead may require a smaller conductor than a long lead carrying the same current.
Does longer welding cable need to be thicker? Usually, yes. Increasing cable length increases resistance and voltage drop. A larger cross-sectional area reduces resistance.
Why are welding cable sizes given in mm²? The mm² value represents the conductor cross-sectional area. Larger cross-sectional areas generally provide lower resistance and greater current-carrying capacity.
Do I calculate voltage drop using one cable or both cables? For a normal welding circuit, both the welding lead and return lead form the current path, so both should be included.
Does duty cycle affect welding cable size? Yes. Thermal loading depends on how long current flows. The applicable cable manufacturer's rating should be used for the actual duty cycle.
Can I use this calculator for aluminum welding cable? This calculator uses copper reference resistance and ampacity values. Aluminum cable requires different electrical and installation data.
What happens if welding cable is too small? An undersized cable can experience excessive heating, increased voltage drop and reduced performance. Severe overheating can create a safety hazard.
Can a larger welding cable be used? Yes, subject to connector compatibility, flexibility requirements, physical routing and the equipment manufacturer's requirements. A larger conductor generally reduces resistance and voltage drop.
Is this calculator a substitute for cable manufacturer's specifications? No. It is an engineering estimation tool. Actual cable ratings depend on the specific product and installation conditions.
Should the work clamp cable be the same size? The return path should be sized appropriately for the welding current and operating conditions. Undersizing the return lead can create the same type of resistance and heating problems as undersizing the welding lead.