I have recently had a chance to purchase a used tank but the owner does not know how many gallons it is. The size of it is 13 x 30½. Does anyone know how many gallons this tank is? Thank you!

You need one more measurement in order to calculate the gallons. Length by height by depth.

OK. Thank you bigkj. I'll see if I can get them. I was just hoping someone had a tank with these measurements that could just tell me how many gallons it holds.

http://www.kokosgoldfish.com/converter.html

Koko has a very convenient convertion chart and program right here on the website. Just type in your measurements and away you go!

The tank volume calculator on the conversion page here at Koko's does not return the correct tank volume.

The calculator not only does not calculate the correct volume in US gallons but it also gives the same answer when using the UK gallons or liters calculator.

For example: a tank 30" X 12" x 12" is sold as a 20 gallon long tank. The actual volume of this tank is 18.70 gallons. The calculator on the conversion page says this tank is 15.58656 US gallons, 15.58656 UK Gallons, and 15.58656 Liters.

Another example a tank 48" X 18" X 24" is sold as a 90 gallon tank. The actual volume is 89.76 US gallons. The tank volume calculator on the conversion page says this tank would hold 74.815488 US gallons, UK gallons and liters.

Until Koko has the opportunity to correct the formulas for the tank volume calculators... The correct formula for calculating the volume of a rectangular tank is. (length in feet X width in feet X height in feet) X 7.47 or (length in inches X width in inches X height in inches / 1728) X 7.47

Rick