How big is my aquarium?

Question
i recently got a new aquarium from my cousin how many gallons is it? Heres the dimensions 30"L * 12 3/4"H * 12 1/4"W

Answer
Hi Matt

Sounds like it's a 20 gallon long.  

Here's what I size for figuring out tank sizes:

http://www.cichlid-forum.com/articles/aquarium_sizes.php

This one says about 19 gallons:

http://www.fishlore.com/ConversionCalculator.htm


Christy