Here's the size chart for choosing your new diving fins. The size is primarily selected based on your regular shoe size (EU).
It's important that the fin fits securely on your foot without pinching. If it's too loose, you risk chafing and reduced power transfer, which means you'll need to exert more effort while swimming. If it's too tight, you might experience cramping in your foot.
The chart also includes information on the total length of the fin (measurement A), which is handy to know if you’re planning to pack them in a suitcase for a vacation.