Aquarium Calculator - Calculate Fish Tank Volume

It is important to know the your aquarium size so that you can figure out what fish you can keep in it. Ideally, you have researched your fish first and then picked your tank size to meet their needs.

In your research you will come across articles written by people using a different measuring system than you (english or metric) and the converters on this page can quickly help you perform these conversions.

There are several calculators on this page and you can use the quick links below to jump to the one you need.

Quick Jump Menu:

Rectangle Fish Tank Volume in Gallons

rectangular aquarium calculator
Fish Tank Length in Inches:
Fish Tank Width in Inches:
Fish Tank Height in Inches:
Aquarium volume is:
US Gallons
UK Gallons

Next: Get Fish Stocking Suggestions for aquariums this size.

Cylinder Aquarium Volume

cylinder aquarium calculator
Fish Tank Height (h) in Inches:
Fish Tank Radius (r) in Inches:
Aquarium volume is:
US Gallons
UK Gallons

For cylinder style aquarium stocking ideas: 3 Gallon Cylinder ideas?

Hexagon Aquarium Volume

hexagon aquarium calculator
Fish Tank Height in Inches:
Length of One Side in Inches:
Aquarium volume is:
US Gallons
UK Gallons

For hexagon stocking ideas: Fish that do well in a hexagon tank

Heater Size

Enter Tank Gallons:

Enter Temperature Change Required (tank temperature minus room temperature):

Heater(s) size needed:

*Always unplug heaters before working on your aquarium! Please note that these heater size recommendations are approximations. Tank wall thickness and whether or not you use a lid or top on your aquarium could affect the heater size needed.

Chiller Size

Enter Tank Volume In Gallons:

Enter Temperature Drop Needed:

Chiller size needed in HP (horsepower):

*The formula used for calculating chiller size is: volume in gallons * 8.34 weight of 1 gallon of water * temperature pull down needed * 20% padding factor. It's better to use an oversized chiller (hence the 20% padding factor in the calculation) than an undersized one to ensure it lasts longer and doesn't have to work as hard and other factors that could impact the efficiency of the unit such as ambient room temperature.

Fahrenheit to Celsius

Enter °F:
= °C

Celsius to Fahrenheit

Enter °C:
= °F

Gallons to Liters

Enter Gallons:
= Liters

Liters to Gallons

Enter Liters:
= Gallons

Inches to Centimeters

Enter Inches:
= Centimeters

Centimeters to Inches

Enter Centimeters:
= Inches

UK Gallons to US Gallons

Enter UK Gallons:
= US Gallons

US Gallons to UK Gallons

Enter US Gallons:
= UK Gallons

Meters to Feet

Enter Meters:
= Feet

Feet to Meters

Enter Feet:
= Meters

Meq/L to dKH CaCO3 (ppm)

Enter Meq/L:
= dKH and
CaCO3 (ppm)

dKH to Meq/L and CaCO3 (ppm)

Enter dKH:
= Meq/L and
ppm CaCO3

CaCO3 (ppm) to Meq/L and dKH

Enter CaCO3:
= Meq/L and

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Next: Read about Saltwater Aquarium Supplements.

Site References :
Wikipedia - for some of the formulas used.

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