As a surfboard builder I firmly believe there are other aspects more important than volume, however this is an easy concept to understand. Volume refers to how well your board will float you. More volume = easier to paddle and catch waves but harder to duck dive and perform "rad" maneuvers. (whatever that is :) For the East Coast, foam or volume is your FRIEND. The more the better in my humble opinion that's why mini simmons and mid length designs are so fun in Florida surf conditions...I'm getting off track so lets just refer to the chart below as a basic guideline, remember talk to your local board builder and get the right volume for your size, ability and the design you are looking for.