What size needles does '5mm' mean?

How-to Questions
1

This is a pattern for moccasin slippers… but the only ‘size’ given for needles is ‘5mm’… please can anyone help me so I can get started casting on? Thanks PS it is a free pattern on many sites… online
I will use American circulars for doing these.
God Bless on this holiest of holy days!
Sr. Bridget

2

These are the equivalent of US size 8. Here’s a chart with needle sizes.

3

Thank You! I really appreciate the reference to the chart
Sr. Bridget