In reply to ibexguiding:
Usually you will find that companies tend to use only hand circumference measurement which works ok for a lot of folk, but can be a bit hit or miss if hand/finger and thumb length is more or less than what each company decides is the “average”.
The best way as usual is try out the gloves in question and buy size that suits you best. Sometimes gloves are made small or large even when based on measurement, plus you as personal preference may prefer tighter or looser fit. If your buying to layer then you will need to consider whether to size up for over layering when appropriate. Different models of gloves from the same manufacturer can be widely different in their fit unfortunately.
The starting point is measure your hand width (circumference in inches!) on your dominant hand just below knuckles with fingers bent and use that in the manufacturer’s sizing chart to work out what should be the best size, then try them on.