A quick calculator so you can determine the size of the aquarium you are shopping or looking to purchase. The methods below will give you cubic measures such as ft 3 or m 3 depending on your units of measure. Quickly calculate the volume of an aquarium using dimensions. Our calculator supports cube shaped aquariums and calculates the volume by multiplying the length, three times. Methods to calculate the volume of tanks and the volume of a liquid inside a tank Actual water and oil tanks may not be perfect geometric shapes or might have other features not accounted for here so, these calculations should only be considered estimates. These tank shapes are calculated assuming exact geometric solid shapes such as cylinders, circles and spheres. Tank volume calculations are based on tank geometries shown below. fluid gallons, Imperial (UK) gallons, cubic feet (ft³), metric liters and cubic meters (m³). Use this aquarium calculator to measure the volume of the fish tank and determine how much water you need to fill up your aquarium box. Current Water Capacity (with substrate): This reveals the effective water volume, accounting for the displacement caused. dimensions in feet (ft) or inches (in), or metric dimensions in meters (m) or centimeters (cm). The calculator provides you with three key pieces of information: Water Capacity (without substrate): This tells you how much water your aquarium can hold, excluding the substrate, in liters, US gallons, and imperial gallons. Use this calculator to find the water surface area, the capacity, and the glass surface area of your fish tank based on its dimensions and shape. Estimate the total capacity and filled volumes in gallons and liters of tanks such as oil tanks and water tanks.