Stick Welder Amperage Chart: How Many Amps to Weld 2mm to 12mm Steel

Quick answer: A useful rule of thumb is roughly 40A per millimetre of electrode diameter: about 70–100A for a 2.5mm rod, 110–140A for 3.2mm and 150–190A for 4.0mm. Match the electrode to the steel thickness, set within that band, and fine-tune for position and penetration. Use DC+ for most rods.

By the Towam Equipment Technical Team · reviewed by our in-house welding service department · Published 14 June 2026 · Updated 14 June 2026

The rule of thumb

Stick welding amperage scales with the electrode diameter, not directly with plate thickness — though the two are linked, because you pick the rod size to suit the metal. A widely used starting point is about 40A per millimetre of electrode diameter. Set within the band, then adjust: lower for thin material, vertical or overhead positions, and a little higher for flat, thick sections where you want full penetration. Always stay within your machine's rated output and duty cycle.

Amperage chart by electrode and steel thickness

Steel thickness Electrode diameter Typical amperage Notes
2–3mm 2.0mm 50–80A Thin sheet; keep heat low to avoid burn-through
3–5mm 2.5mm 70–100A General light fabrication and repairs
5–8mm 3.2mm 110–140A Most common workshop range
8–10mm 4.0mm 150–190A Heavier sections; may need multiple passes
10–12mm and up 4.0mm (multi-pass) or larger 170–190A+ per pass Edge preparation and multiple passes for full penetration

Figures are typical starting points for common mild-steel electrodes. Always follow your electrode manufacturer's data sheet and your welding procedure; thicker plate is welded in multiple passes rather than at a single very high current.

Polarity — getting it right

Polarity affects penetration and arc stability, and the wrong setting gives a poor, wandering arc. As a general guide:

  • DC electrode positive (DC+ / DCEP): the most common setting for stick welding, giving deeper penetration. Used for E6010, E7018 and most general work.
  • DC electrode negative (DC− / DCEN): shallower penetration and a faster deposit on thin material; used for some rods and applications.
  • AC: available with some electrodes such as E6013 and useful where arc blow is a problem. All current 555 inverters are DC machines.

Always check the electrode packaging for the correct polarity — it is printed on every box.

Matching thickness, rod and machine

Picking the amperage is only half the job; the machine has to sustain it. A welder rated at 180A but with a low duty cycle at that current will overheat on thick plate, so check the duty cycle rated to EN/IEC 60974-1 at 40°C. For thin and light work the 555 MMA-300 PRO (160A) is ample; for heavier sections and structural work the 555 MMA-400 PRO (180A, adjustable Arc Force) or the 555 ARC 250 GT (210A) give more headroom. See our duty cycle guide and the full MMA stick welders range.

Frequently asked questions

How many amps do I need to weld 6mm steel?

A 3.2mm electrode at roughly 110–140A is a good starting point for 6mm steel. Set within the band, run a test bead and adjust for position and penetration.

Can I weld 12mm steel with a stick welder?

Yes, but in multiple passes with edge preparation rather than one very high-current pass. Use a 4.0mm rod around 170–190A per pass and a machine with the duty cycle to sustain it.

What polarity should I use for E6010 and E7018?

Both run best on DC electrode positive (DC+). Check the rod box to confirm, as a few electrodes call for negative or AC. All current 555 machines are DC.

Why is my arc unstable even at the right amperage?

Common causes are the wrong polarity, a damp electrode, a poor earth connection or a machine struggling at its duty-cycle limit. Check each in turn. For cellulosic E6010 you also need a machine rated to run it, such as the 555 ARC 250 GT.

Is thicker plate just a matter of turning the amps up?

No. Beyond a point you switch to multiple passes with edge preparation rather than ever-higher current, which would overheat the rod and the machine. Build the joint up in controlled passes.

Need help dialling in amperage or choosing a machine for your steel thickness? Message our technical team on WhatsApp.

Towam Equipment Trading · in-house UAE service · WhatsApp +971 50 767 0682 · sales@towam.ae · towam.ae. Figures rated to EN/IEC 60974-1 at 40°C.