How To Check You Have The Right Cable Size
Work out which cable size to choose for your wiring job.
19 January, 2021 by ​, Brian Smith

Unsure which cable size to choose for your wiring job?

Here are some easy steps you can take to make sure!

# 1. Find out the voltage

Start off with the Voltage the fitting is operating at. 240V? 12V? 110V?

# 2. Find out the total wattage

Next, work out the total number of Watts drawn (e.g. quantity of light bulbs x their wattage).

Getting this info will enable you to work out the Amps drawn by the fitting in Step 3.

# 3. Calculate the current

To calculate the Current (in Amps) drawn by a fitting, divide the Power (in Watts) by the Voltage (in Volts).

# 4. Work out the conductor size

Now you know the Current, you can work out the cable conductor size you need from the table below.

# Current Ratings for Flexible Cables

 Conductor Size, sq mm Max Current, amp 0.50 3 0.75 6 1.00 10 1.50 15

Examples:

## Example 1:

A mains-powered (240V) heater rated at 3000 Watts.

This draws a current of 12.5 Amps. (3000 divided by 240)

From the table above, it will need 1.5 sq mm flex.

## Example 2:

A mains-powered (240V) light bulb rated at 100W

This draws a current of 0.4 Amp (100 divided by 240)

It will need 0.5 sq mm flex.

## Example 3:

A 12V circuit of 20 LED bulbs, each rated at 3W

This draws a current of 5 Amp. [(20 multiplied by 3) divided by 12]

From the table above, it will need 0.75 sq mm flex.

See Our Cable Selection ​, Brian Smith 19 January, 2021