Aquarium Volume Calculator

Shape

Length, cm

Width, cm

Diameter for a cylinder, cm

Height, cm

Glass thickness, cm

Gap below the rim, cm

Substrate depth, cm

Result

Water in the tank, l151.9
Outside volume, l185.9
Filled weight, kg218
Filter output, l/h608
Heater power, W152
A 25% change, l38

A hundred-litre tank holds about eighty

Calculates the real water volume of a tank with the glass, substrate and rim gap subtracted, plus the filled weight and the filter and heater it needs.

Multiply the outside dimensions and you get a number no aquarium ever contains. The glass takes a centimetre or two off each dimension, the substrate takes a layer off the bottom, and the water stops several centimetres below the rim.

The difference matters because everything else is dosed by volume: medication, fertiliser, filter throughput and the water change. Working from the nominal figure means overdosing by a fifth.

What this calculator shows

The real water volume and the outside volume
The weight of the tank once filled, glass and substrate included
The filter flow, heater power and the litres in a 25 percent change

What to keep in mind

Water is a kilogram a litre, substrate about 1.6 and glass 2.5, which is where the filled weight comes from.
Filter throughput is taken as four times the volume an hour and heater power as roughly a watt a litre for a normal room.

FAQs

How many litres are in a 100 × 40 × 50 tank?

Two hundred by the outside dimensions, about 186 inside the glass, and roughly 152 of actual water once the substrate and the rim gap are taken off.

Why does the real volume matter?

Because doses are per litre. Medicating 200 litres of water when the tank holds 152 is a thirty percent overdose, which fish notice.

What filter does a tank need?

A throughput of about four tank volumes an hour for a normal community setup, more for messy fish, less for a planted tank with gentle flow.

Can a tank stand on ordinary furniture?

Rarely. A filled 150-litre tank is over two hundred kilograms on a small footprint, and it needs a stand built for it on a level floor.

Worked example

A 100 × 40 × 50 tank

Input: 100 × 40 × 50 cm, 8 mm glass, 4 cm below the rim, 5 cm of substrate

Output: about 152 litres of water

Note: The outside volume is 200 litres and the inside 186, but only 152 is water. Filled, the tank weighs about 218 kg — which is more than most furniture is built for.

Useful links

All tools in Home & Utilities

Aquarium Volume Calculator

Result

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