If you have beefy hands, width size is more important.

If you have long fingers, finger length is more important.

Step 1: Measure the length of your middle finger on the palmside.

Step 2: Lightly wrap a string/tailor's tape around the widest part of your knuckles.

Remember, your gloves will break in — BUT mostly in the width of the fingers and hand. They don't magically get longer.

Size Middle Finger Knuckle Size
X-Small 2.75" and under 7.25" and under
Small 3.15" and under 7.75" and under
Medium 3.25" and under 8.25" and under
Large 3.3" and under 8.5" and under
X-Large 3.5" and under 9.0" and under
XX-Large 3.5" and OVER 9.0" and OVER