Aquarium Calculator - Calculate Volume (Litres & Gallons) Based on Dimensions

Use our simple Aquarium Calculator below to calculate the volume of your aquarium in liters and gallons based on its size (dimensions in cm or inches):

How much water will the tank size really hold?

Theoretical volume

This is the absolute volume when an otherwise empty tank is filled to the very top edge with water. This is the size that the manufacturer will often state for the aquarium sizes.

Realistic volume

Allows for decor displacement and that the tank won’t be filled to the very top edge. As such this is a far more accurate measurement to use.

How high you fill the water and what you place in the tank will decrease the amount of water volume to a more realistic lower quantity.

For example, a small 2.5 Gallon tank 12 x 6 x 8 holds 2.5 Gallons when completely full to the top. But allowing for the water to be lower than the very top rim, some plants and decorations in the tank the actual realistic volume is more likely to be 2.25 Gallons. Fish tank sizes are easy to calculate using our calculator, just be careful when working out how much water for dosing with any chemicals for pH and GH levels, or sizing filters etc.

When YOU calculate the water volume in the calculator YOU should reduce the HEIGHT as you are not really going to fill it with water to the very top.

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Aquarium Weight

Below is an estimate of aquarium weights comparing empty to full, freshwater or saltwater.

The weights are an estimate because the amount of rock, planting, thickness of glass are assumed figures.
For planting and rocks, this includes any decor, but not fish, so that you can see what we have assumed.

A gallon of freshwater at 39.2ºF, or 4ºC and a specific gravity of 1.000 weighs 8.3454 lbs.

The weight of the water will increase directly proportionate to the weight of the salt being dissolved in the water.
1 gallon of water 8.3454 lbs times the specific gravity of say 1.025 equals 8.5540 lbs (8.3454 x 1.025 = 8.5540).

1 gallon of saltwater at 1.025 specific gravity equals 8.554 lbs.

For more information on water weight see our post ‘How much does a gallon of water weigh?’

For your own tank you decide how much planting etc will be added and alter the weights to suit your needs.

SMALL-SIZED AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
2 1/2 gallon	12″ x 6″ x 8″	3	3	26.9	27.4
5 gallon	16″ x 8″ x 10″	7	10	58.7	59.8
10 gallon “Leader”	20″ x 10″ x 12″	11	15	109.5	111.5
15 gallon	24″ x 12″ x 12″	21	25	171.2	174.3
15 gallon High	20″ x 10″ x 18″	22	25	172.2	175.3

MID-SIZED AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
20 gallon High	24″ x 12″ x 16″	25	30	221.9	226.1
20 gallon Long	30″ x 12″ x 12″	25	30	221.9	226.1
25 gallon	24″ x 12″ x 20″	32	40	280.6	285.9
29 gallon	30″ x 12″ x 18″	40	45	327	333.1
30 gallon Breeder	36″ x 18″ x 12″	48	48	346.4	352.6
40 gallon Breeder	36″ x 18″ x 16″	58	60	451.8	460.2
40 gallon Long	48″ x 12″ x 16″	55	60	448.8	457.2

LARGE AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
50 gallon	36″ x 18″ x 19″	100	70	587.3	597.7
55 gallon	48″ x 13″ x 21″	107	75	641	652.5
65 gallon	36″ x 18″ x 24″	126	90	758.5	772
75 gallon	48″ x 18″ x 21″	140	110	875.9	891.6
90 gallon	48″ x 18″ x 24″	160	120	1031.1	1049.9
125 gallon	72″ x 18″ x 21″	206	130	1379.2	1405.3
150 gallon	72″ x 18″ x 28″	338	140	1729.8	1761.1
180 Gallon	72″ x 24″ x 25″	350	170	2022.2	2059.7
225 Gallon	72″ x 27.5″ x 27.5″	360	190	2427.7	2474.7