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Watts to Amps Calculator (230 V)

Convert appliance wattage into current on a 230 V supply for fuse, breaker and cable selection.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Current draw

13.04 A

High confidence

I = P ÷ V at 230 V single phase. Check the result against the circuit's protective device rating and, on long runs, against voltage drop.

Conversion factor applied
0 A per W

This is the check made before adding a load to an existing circuit, or when choosing a plug fuse. Dividing watts by 230 gives the current, and that figure drives everything downstream: the fuse rating, the breaker, the conductor size. Two things frequently get missed. Fuse selection should be the smallest standard rating above the draw rather than the largest that fits — a 3 A fuse on a 700 W appliance protects the flex in a way a 13 A fuse simply does not. And on a long run the current alone is not sufficient to size the cable, because voltage drop accumulates with distance and can require a larger conductor than thermal capacity would demand. Large fixed loads such as electric showers, which can approach 40 A, belong on dedicated circuits rather than being added to existing ones.

Add the equipment this sizes

This result is a specification — 13.043 A — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • I = P / V, rearranged from P = V x I
  • UK plug fuses are manufactured in 3 A, 5 A and 13 A ratings (BS 1362)

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Frequently asked questions

Which plug fuse should I fit?
The smallest standard rating above the appliance's current draw. BS 1362 fuses come in 3 A, 5 A and 13 A. A 700 W appliance drawing about 3 A takes a 3 A fuse; fitting 13 A to everything means the flex is unprotected until a much larger fault develops.
Why is my shower on such a large cable?
Because electric showers are among the biggest single-phase loads in a house. A 9 kW shower draws roughly 39 A at 230 V, which needs its own circuit, a substantial conductor and an appropriately rated device — it is not something to add to an existing ring.
Does cable length affect this?
Not the current, but it does affect whether the cable is adequate. Voltage drop accumulates over distance, and a long run may need a larger conductor than the current alone would suggest in order to keep the drop within limits.