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Home › Selection guide › 16A / 32A / 63A / 125A: how to pick the rating in three steps

16A / 32A / 63A / 125A: how to pick the rating in three steps

The rating follows the equipment current with at least 20% headroom: 16A ≈ 7.5kW, 32A ≈ 15kW, 63A ≈ 30kW, 125A ≈ 60kW (three-phase 380V). With the conversion formulas and the four commonest mistakes.

Conclusion: the rating is decided by one thing — the rated current of the equipment — with at least 20% headroom. The usual ratings (estimated for three-phase 380V):

RatingRoughly carriesTypical useModels we stock
16Aup to ≈ 7.5kWSmall machine tools, pumps, fans, workstation power745
32Aup to ≈ 15kWMedium machinery, welders, packaging machines, cold stores569
63Aup to ≈ 30kWLarger machinery, temporary distribution, container socket boxes201
125Aup to ≈ 60kWMain feeds, large machinery, site distribution79 (mostly IP67)

Estimated at three-phase 380V and power factor 0.85, already allowing for "continuous current ≤ 80% of rating". Motor loads also need starting current considered.

Three steps

  1. Work out the current: the nameplate rating is best; if you only have power, convert with the formulas below and round up to the next standard rating (16 / 32 / 63 / 125A).
  2. Then the poles: is a neutral needed? Three-phase with neutral = 5-pole (3P+N+earth), three-phase without = 4-pole (3P+earth), single-phase = 3-pole (2P+earth). See counting poles.
  3. Finally mounting and IP rating: wall (wall-mounted) / equipment panel (add-on = panel-mounted = flush) / cable end (connector); IP44 is enough in a dry workshop, outdoors, wash-down and cold stores need IP67.

Power to current (quick field estimate)

SupplyFormulaQuick rule
Three-phase 380VI = P ÷ (√3 × 380 × 0.85)current A ≈ kW × 1.8
Single-phase 220VI = P ÷ (220 × 0.85)current A ≈ kW × 5.4

Examples: 11kW three-phase motor → 11 × 1.8 ≈ 20A → take the 32A rating (16A is not enough); 5.5kW three-phase pump → ≈ 10A → 16A is enough (still leave headroom for a motor); single-phase 3kW heater → 3 × 5.4 ≈ 16A → right at the 16A limit, going to 32A is safer.

What each rating looks like in our stock

RatingCommonest polesCommonest IP rating
16A3 / 4 / 5-pole all available (including SCHUKO and low voltage)Mostly IP44, IP67 also stocked
32AMostly 4 / 5-poleAbout half IP44, half IP67
63A4 / 5-poleMostly IP67
125A4 / 5-poleAlmost all IP67

The four mistakes people make

  1. Copying the old plug instead of reading the equipment current — the machine was upgraded, the cable was not, and that is a latent fault.
  2. No headroom: a 16A device run at 16A continuously heats the terminals and shortens life. 20% is the minimum.
  3. Looking at current only: 32A comes in both 4-pole and 5-pole variants (see 93xx cross-reference) and the wrong one will not fit.
  4. Ignoring cable size and terminals above 63A: 125A has requirements for conductor cross-section and terminal torque — confirm the cable at the same time.
If unsure, send us three things: (1) a photo of the nameplate or the power rating (2) three-phase or single-phase, and whether a neutral is needed (3) where it is mounted (dry / outdoor / wash-down). We come back with rating + poles + IP rating + mounting, plus product photos and datasheets.

Related: counting poles · add-on = panel-mounted = flush: the names · IP44 vs IP67

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