Aquarium volume is calculated using the dimensions of the glass or plastic walls. The length, width, and height are important if you don’t know the water volume of your tank. With that information you will be able to calculate the amount and weight of the water held by an aquarium. The calculations for aquarium water volume use the geometric formulas for 3 dimensional shapes.
By calculating the fish tank volume you will know you how many fish you can keep, the filter size you need, how strong your lights should be, and the power of the heater required. And when adding medications you’ll provide the right amount per gallon of water to cure your fish without stressing them.
How Many Gallons is My Fish Tank?
The following fish tank calculator tool uses the dimensions of your tank to list the volume. Most aquariums are rectangles so you need the length, width, and height. Type in each of these measurements into our aquarium calculator and press calculate.
Aquarium Volume Calculator
Enter the length, width, and height to calculate the volume in liters:
How to Measure a Fish Tank?
To measure a fish tank and find the volume you will need a ruler first. A standard ruler will work, as will a meter stick, yardstick, or tape measure. Make sure when measuring that you use the same units for each dimension. And when calculating the volume in inches or gallons from dimensions you’ll need to consider them as square3 units since volume is a 3 dimensional calculation.
For a standard sized aquarium you can also refer to my charts on tank volume and size instead of the aquarium gallon calculator above. The majority of rectangular or square tanks that are not custom made will have standard dimensions. That includes the glass aquarium you picked up at a yard sale whose volume the owner was unsure of.
Fish Tank Size Calculator
Aquarium dimensions are an important step in determining how many gallons of water your fish tank holds. Rectangular prisms are the most common geometric shape. But fish tanks also come as cubes, cylinders, half cylinders, and quarter cylinders.
Small desktop fish tanks take on these flexible forms since they are easy to make space for. Plus it isn’t as complicated to warp acrylic or glass into complex forms at this size.
Larger aquariums are usually cylinder-shaped or bow fronts. These designs are more stable while offering a departure from the usual rectangular prism.
Here are the formulas involved in calculating tank volume for a given shape.
Rectangle Volume Calculator
The volume of a rectangular prism uses the following formula:
Volume rectangle tank = length x width x height. The end result will be in cubic measurements (unit3), which are three dimensional. An aquarium that is a 20in x 10in x 12in rectangle will have a volume of 2,400 cubic inches (2,400 in3). Once you have that, this unit conversion tool will convert cubic inches to gallons. Giving us 10.39 gallons for the dimensions of a standard 10 gallon fish tank.
Square Tank Calculator
To calculate the volume of a square tank you use the same formula:
Volume square tank = length x width x height. Take the final result, which will be in cubic measurements (unit3). An average rimless betta fish tank will be 20cm x 20cm x 20cm. With a final volume of 8,000 cm3. Thanks to our conversion tool we get a volume of 2.1 gallons.
Bowfront Aquarium Tank Calculator
Bowfront aquariums use a more complex formula due to the curved panels.
Volume bowfront = height × width × length + 0.5 × r² × (α - sin(α)) × heightα is the central angle of the circular segment, expressed in radians. r is the radius of a circle, squared. The angle of α is calculated using the formula α = 2π – 4β. The unit β is calculated through the following: tan(β) = 0.5 × length / (full_width – width).
For a corner bowfront, which does not have a flat back, the formula is:
Volume corner bowfront = (0.5r² × (α - sin(α)) × height)/2Cylinder Aquarium Gallon Calculator
We will need three formulas to describe the volume of a cylindrical fish tank. For a full cylinder with a circular base we use:
Volume cylinder = π × (diameter / 2)² × heightSo for a cylinder aquarium that’s 50 inches tall and 20 inches in diameter, we get:
V = π x (20 / 2)² × 50. Resulting in 4,751.66 in3, which is equal to 20.57 gallons.
A half cylinder has a circular base cut in half. Use the same formula as above and then divide the end result by 2.
A quarter cylinder is a wedge-shaped fish tank where the triangular back is placed into the corner of a wall. We use the radius instead of the diameter for this calculation.
V quarter cylinder = π × radius² × height / 4Fish Bowl Volume Calculator
A fish bowl is a glass or plastic tank that has no straight lines to it. We need to use the formula for the volume of a sphere instead.
V fish bowl = (4/3) × π × r³r equals the radius, which might be difficult to measure. If you don’t know the radius of your fish bowl, you can measure the circumference instead. The circumference is a measurement of the distance around the widest part of the bowl. Use either a string and a ruler or measuring tape. Once you have the circumference use the following formula to calculate the radius:
r = circumference / (2 × π)So for a fish bowl that has a circumference of 50 inches, the interior radius is going to be 7.96 inches. V fish bowl = (4/3) x π x 7.96³. Resulting in a volume of 2112.66 in³ or 9.14 gallons
Most fish bowls have a flat region at the top for adding water or fish food so the formula is not exact. Fish bowls are not what I recommend keeping pets in anyway. They are sold to beginners who think a bowl does not need a filter or heater. Goldfish are the most common bowl fish. These pets reach 8 to 20 inches in length and will outgrow any bowl you provide them with.
How Many Fish in a Tank Calculator
Knowing how many fish to keep in a fish tank is not as simple as using a formula. You have to take into account the temperament and activity level of the fish you have in mind.
| Fish Tank Size (Gallons) | Dimensions (inches) | Suitable Fish Species |
|---|---|---|
| 5 | 16 x 8 x 10 | Betta, Dwarf Gourami, Small Shrimp |
| 10 | 20 x 10 x 12 | Neon Tetra, Guppy, Harlequin Rasbora |
| 20 | 24 x 12 x 16 | Dwarf Cichlid, Platy, Zebra Danio |
| 29 | 30 x 12 x 18 | Swordtail, Angelfish, Rosy Barb |
| 40 | 36 x 18 x 16 | Cherry Barb, Bristlenose Pleco, Rainbowfish |
| 55 | 48 x 12 x 21 | African Cichlid, Discus, Kribensis |
| 75 | 48 x 18 x 21 | Silver Dollar, Jack Dempsey, Firemouth Cichlid |
| 90 | 48 x 18 x 24 | Oscar, Red Devil Cichlid, Peacock Cichlid |
| 125 | 72 x 18 x 21 | Arowana, Frontosa Cichlid, Tiger Shovelnose Catfish |
| 150 | 72 x 24 x 21 | Flowerhorn, Green Terror Cichlid, Oscar |
The old adage of “one inch of fish per gallon of water” is not applicable all of the time. It does work if you are keeping small fish like tetras, guppies, danios, and so on. But the total mass of a fish is also important because more massive fish release much more waste. One 10-inch oscar fish does not equal ten 1-inch neon tetras. The neons would be good additions to a 10 gallon aquarium but not the oscar. An oscar this large would need 75 gallons of space.
For fish that are 1 to 2 inches long, the formula works as long as you also consider their behavioral and biological needs. Do research to see whether your chosen fish might compete for territory or have different water parameter requirements. If so then you shouldn’t be mixing them. For larger fish, stick to the guidelines given in aquarium fish species profiles.
An aquarium calculator allows you to find the volume of a tank. Once you have the volume you have a better idea of how much water to add, how much gravel to fill it with, and the fish carrying capacity of your setup. All that’s required are the aquarium dimensions plugged into the right volume calculator formula.
FAQs
You need the fish tank dimensions to calculate the volume of an aquarium. For a rectangular or square shaped fish tank, you multiply the length x width x height. The end result will give you a cubic number, which could be converted to gallons for easier comprehension.
A 48inx18inx18in fish tank uses the standard aquarium volume formula. By multiplying these numbers together we get a total volume of 15,552 in3. Converted to gallons we get 67.32 gallons, which is an unusual size between a normal 55 and 75 gallon aquarium.
