POST YOUR HAND SIZE!
I don't know exactly what that is good for but here you are:
Length: 210 mm or about 8.3 inches (the palm itself to where the middle finger starts is 120 mm or about 4.7 inches)
Width: 105 mm or about 4.1 inches
(both hands equal)
Flexibility seems a lot more important to me. How much is your
workable stretch between the fingers without tension elsewhere, for example, finger proportions (how long are the individual fingers), and as
outin said: how is your thumb situated. Some people may be able to stretch c-f, for example, but are unable to take in Db-f, especially with other notes in between.
Where do I measure for the width??
Where the knuckle bridge is (so not where the fingers seem to start in the palm of the hand, but where the two creases are in the middle of the palm).