Our jewellery sizes follow the French standard. Check your size in the Size Guide that you find in every product page.
The fit of a ring varies according to its design. More or less as happens with clothing and footwear.
The fit refers to a ring's adaptability and closeness to the finger, and, regardless of size, can be defined as follows:

 

Standard: close to the finger's actual size. The size matches the measured size.
Tight: tends to resist when coming off. It may be necessary to size up.
Roomy: leaves space between the finger and the ring, may be too loose. It may be necessary to size down.