On this page, you can download the official ampacity tables from the brand new ISO 13297 standard as PDF. They are the basis for calculating wire sizes on your boat when you are working in the metric system.
If you are in the US, you might want to check out the ABYC Ampacity Tables instead.
How to use the ISO ampacity tables?
- 1Select the column with the correct insulation temperature rating for your cable
- 2Go down until you reach the row with the cross-sectional area of your conductor
This gives you the ampacity for an unbundled cable outside of an engine compartment.
- 3If part of the cable runs inside an engine space, multiply the ampacity with the derating factor from the lower small table
- 4If the cable runs in a bundle of 4 or more conductors, multiply the result by the corresponding factor from the upper small table
If you want to know the required size of wire for a certain amperage, just do the whole process in reverse.
Instead of doing the calculations by hand, you can also use the BOATHOWTO Wire Size Calculator.
If you want to know more details on the choice of cables for your boat, the required overcurrent protection and much more, check out our Boat Electrics course!