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For stick (SMAW) and TIG on carbon steel, a common rule is roughly 1 amp per 0.001 inch of electrode diameter. A 1/8-inch (3.2 mm) rod typically runs 90–130 amps depending on position and joint.
Amps ≈ Electrode diameter (in) × 1000 × 0.9 to 1.1Thin sheet under 1/8 inch needs lower amperage and faster travel to avoid burn-through. Thick plate above 1/4 inch requires higher current, preheat for some alloys, and often multiple passes.
Base amps ≈ Material thickness (mm) × 30–40 for flat position carbon steelVertical and overhead positions typically use 10–15% less amperage than flat. Open-root groove welds may need lower heat input; fillet welds on thick members may need higher current for proper penetration.
Adjusted amps = Flat-position amps × Position factor (0.85–1.0)Updated: July 2026
A 1/8-inch (3.2 mm) E7018 electrode on 3/16-inch plate in flat position typically starts at 110–125 amps. Adjust down for vertical-up or up for thicker multi-pass fillets.
0.030-inch wire on 14-gauge (1.9 mm) steel often runs 90–110 amps at 18–20 V wire feed speed. Use lower amps on lap joints to prevent blow-through.
A 1/16-inch tungsten with 1/16-inch filler on 2-inch pipe root gap commonly uses 70–90 amps DCEN. Increase for hot pass and cap while maintaining interpass temperature limits.
Reduce amperage 10–15% for vertical-up and overhead work. The molten pool sags under gravity; lower heat keeps the puddle controllable and reduces undercut.
Always cross-check electrode diameter, base metal thickness, and joint type together. A 3/32-inch rod at 140 amps on thin sheet will burn through regardless of what a general chart suggests.
Correct welding amperage depends on base metal thickness, joint design, electrode diameter, and process. Too little current causes lack of fusion; too much causes burn-through and excessive spatter. This calculator estimates starting amperage for common welding processes so you can dial in settings faster.