Hook sizes and their designations vary from country to country. When following the recommendations in a pattern or on a ball band, make sure to check which size convention is being used.
Tell us your thoughts below.
This chart of hook sizes is very helpful and I use it a lot. Would it be possible for you to publish a list of which size hook is best to use for the various yarns and threads? For example size 1.25mm hook for size 20 cotton and 4mm hook for DK yarn.