1 gallon = 231 in
1 inch = 2.54 cm
Honestly, I would say it will fill up because if your solving for the amount of centimeters in a gallon then the gallon would fill up. It just makes sense to me, don't know if it's correct because what I did was take the amount of centimeters in a inch and multiply it by the total amount of inches in a gallon.
HOPE THIS HELPS! ^_^