Did you mean in cm or inches? Here's both.
60cm x 30cm x 30cm = 54L => 12 UK gal (15 US gal).
60" x 30" x 30" = 884L => 196 UK Gal (232 US gal).
Calculating the volume of a tank is:
length * width * height in cm / 1000 => liters.
length * width * height in inches / 290 => UK gallons
length * width * height in inches / 232 => US gallons
length * width * height in inches / 61 => Liters.
UK Gallons * 1.25 => US gal
US Gallons / 1.25 => UK Gal
UK Gallons * 4.5 => liters
US Gallons * 3.8 => liters
Liters / 3.8 => US Gallons
Liters / 4.5 => UK Gallons
These numbers are approximations, but it gets you close enough for most purposes. [Ideally, you should subtract the thickness of the glass, since the measure of the tank is almost always the OUTSIDE measure. On small tanks with thin glass it makes little difference, but for bigger tanks, it tends to take a few liters away].
Note also that most people don't fill the tankt ALL the way to the edge, but there's usually a couple of centimeters or about an inch of gap between the top of the water and the top of the glass (water tends to escape when it gets very close to the top
).
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