How to Calculate the Surface Area and Volume of a Fish Tank

The wider the water surface, the higher the oxygen level in your tank. Consequently, when you determine the number of fish in your tank or choose an aquarium water pump, it is necessary to know the aquarium size, surface area, and volume of your fish tank. But do you know how to do aquarium size calculations? If you don’t know, this article will give you answers!

Content Table

Aquarium standard size and weight

To begin with, we are likely to share how to calculate the volume of an aquarium, and some standard sizes of rectangular aquariums.

How to calculate the fish tank weight?

In general, the height of the water capacity is 5 cm lower than the height of a fish tank. You can calculate the weight by this aquarium size calculate formula:

  • The weight of water capacity = (length * width * height)/1000

[Height here refers to the height of the water in your tank.]
aquarium size calculator
Attention, here are also tips for the formula mentioned above.

Items Unit
Length/width/height Centimeter (cm)
The weight of water capacity  Liter (L)

For example, provided that the parameters of your tank are as follows:

  • Length: 60 cm
  • Width:45 cm
  • Height (the height of water): 40 cm

Then the weight of water capacity should be (60*45*40)/1000=108L, which is equal to about 30 gallons.

Standard sizes of rectangular aquariums

In this part, we will provide you with the main standard sizes and volumes of rectangular aquariums.

Dimensions of the aquarium
(unit: cm)
The volume (unit: L) The volume (unit: gallon)
(Approximate value)
40*30*30 30 8
50*30*30 37.5 10
50*40*40 70 20
60*30*30 45 12
60*40*40 84 22
60*45*45 108 30
80*40*40 112 30
90*40*40 126 33
90*45*45 162 43
100*45*45 180 48
100*50*50 225 60
120*50*50 270 72
120*60*60 396 105
150*50*50 337.5 90
150*60*60 495 130
180*60*60 594 157
200*60*60 660 175
200*80*80 1200 317

Tank sizes, width, and length give the surface area

Provided you know the length and width of your tank, it is easy to calculate the tank surface area. The following are the formulas:

  • The surface area = 2length*width+2 (length*height)+2 (width*height) [With a cover]
  • The surface area = length*width+2 (length*height)+2 (width*height) [Without a cover]

Pointers for the above formula:

Items Unit
Length/width/height Centimeter (cm)
The surface area Square centimeter

Next, according to the surface area, can we speculate the aquarium water pump flow rate and the watts of your tank? That seems not feasible. However, we can speculate the water pump flow rate and watts if we know the volume of water in your aquarium. In general, the water pump flow rate is 3–5 times the water capacity in the tank. After we know the water pump flow rate, we can know the watts of the water pump based on the product specification.

For instance, provided your tank is 100cm in length, 40cm in width, and 60cm in height, then the volume is about 240L. [(100*40*60)/1000=240L] the water pump flow rate should be 720L/H or 1200L/H. [240*3=720, 240*5=1200] Take DC Water Pump as an example, 25W, or 40W will be great options.

Will my floor hold my aquarium?

Generally, an aquarium will not fall unless the fish tank is too heavy. Usually, a large fish tank should be located in a place with a large load capacity, while small tanks can be placed on the table. If you place your aquarium on the floor, it is recommended to place them near the load-bearing wall.
fish tank calculation
The standard live load of the residential floor is 2 KN per square meter, which means that it can stand for 200 KG of each square meter at the same time. The live load refers to the total weight of objects you put on the house, including furniture, people, aquariums, and something like that. On the other hand, it is better to put a wooden board between the bottom of your fish tank and the floor surface. Besides, it is also feasible to distribute the load by adding more load-bearing aquarium stands.

Moreover, it is recommended to keep your aquarium no more than 50cm in height, as the higher the fish tank, the higher the pressure on the floor. Most residential floors can hold a 125-gallon aquarium. Aquariums of 55–125 gallons can be placed on the floor with good structure and no defects.

Is there a fish tank size to some fish ratio?

The water capacity & the size of the fish

Usually, one gallon of water can keep one fish of 1cm in length. Suppose that there is 190L water in your tank (50 gallons), then the fish you keep should not be over 10cm in length.

Fish tank size & the number of fish

Since overstock is bad for your fish, it will cause bad water quality, heavy breathing, or some other potential threats. Fortunately, we can calculate the ideal number of fish according to the aquarium tank size.

If the tank water capacity is 10 gallons, you can keep 5 fish between 1-3cm in length, or keep 10 fish in a 20-gallon tank; suppose you want to keep 5cm long fish, you need a 30-gallon fish tank.
fish tank volume calculator


In the end, we are likely to provide you with some pointers. First, you should choose a suitable tank size according to the fish species and fish density. Generally speaking, large fish tanks are better, which can provide more room for your cute fish and make great sense in keeping good water quality and dissolved oxygen. Aside from that, you should set up an ideal filter system, as it can filter debris in tanks and provide a comfortable habitat for your fish.

Finally, thanks for your reading!

Related Topic


Could I put the fish tank on the fifth floor of the residential building? [Fish tank parameters: 1.2m in length, 0.5m in width, and 0.5m in height]

  • The volume of the fish tank= 1.2m*0.5m*0.5m=300L
  • The mass of the fish tank: 300KG
  • Base area of the fish tank=1.2*0.5=0.6 square meter
  • The load-bearing per square meter=300/0.6=500 KG per square meter

If you place the fish tank appropriately, and there are no other objects of high weight, it is feasible to put the tank on the fifth floor of the residential building. Because the floor distributes the load, and the pressure on the floor doesn’t reach 500 kg per square meter.

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