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Wire Gauge Calculator

Get a rough minimum copper wire cross-section for a given current draw.

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Need Minimum cross-section? The Wire Gauge Calculator derives it from Current (A) in one step. For instance, with Current (A) = 16 it returns Minimum cross-section = 2.5 mm².

How to use it

  1. Enter your values: Current (A).
  2. Read the result instantly: Minimum cross-section.

Frequently asked questions

How does the Wire Gauge Calculator work?

It takes Current (A) and derives Minimum cross-section from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

A single value: Current (A). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Current (A) = 16, the calculator returns Minimum cross-section = 2.5 mm². Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Current (A) = 32 instead, Minimum cross-section goes from 2.5 mm² to 10 mm² — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Current (A) = 8, Minimum cross-section comes out at 1.5 mm². The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

How accurate is it, and what are the limits?

This is a rough guide only. Always consult a qualified electrician: real cable sizing depends on run length, insulation type, ambient temperature and installation method.

What is the difference between the Wire Gauge Calculator and the Wire resistance calculator?

This one returns Minimum cross-section; the Wire resistance calculator returns Resistance (Ω). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Voltage drop calculator is the closest one after this: Estimate the voltage drop in a copper cable from its length, current and cross-section.

Further reading

All guides →
How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.ExplainerHow Many Cables Fit in a Conduit? It Is a Code Question, Not a Geometry QuestionThe 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.ExplainerWhat Is Voltage Drop? Why Long Wires Lose VoltageVoltage drop is the voltage lost along a wire due to its resistance. Learn how length, gauge, and current affect it, and why it matters for your circuits.How-toWhat TV Size Is Right for My Room?Turn your viewing distance into a recommended screen diagonal in inches, so a 4K TV fills your field of view without straining your eyes.How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.