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Fish Tank Volume Calculator

Fish Tank Volume Calculator

Volume

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Enter your tank dimensions to see the volume.

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Enter your tank's dimensions to calculate its exact water volume and capacity. Choose your tank shape, pick any unit, and get instant results in litres, US gallons and UK gallons.

What is fish tank volume?

Fish tank volume is the total amount of water an aquarium can hold. For a rectangular tank it equals length times width times height.

Your real water volume is a little lower than the tank's full capacity, because substrate, rocks and decor displace water and you leave a gap at the top. Drag the slider to see how the water volume of a 60 by 30 by 30 cm (54 L) tank changes with fill level.

Formulas behind the fish tank volume calculator

Prefer to calculate the aquarium size by hand? Here is the volume formula for each tank shape. Click a card to try it in the calculator.

For unusual tanks, see a triangular prism volume tool, and note that spherical aquariums (fish bowls) are not recommended for keeping fish.

How to calculate fish tank volume

Measure the length, width and height of your tank, then multiply them together. Change the values below and the diagram and the calculation update instantly.

  1. 1

    Measure length, width and height

    60 x 30 x 30 cm

  2. 2

    Multiply them for cubic centimetres

    60 x 30 x 30 = 54,000 cm³

  3. 3

    Convert to litres and gallons

    54,000 ÷ 1000 = 54 litres (14.27 US gal)

Aquarium shapes

Our fish tank volume calculator supports seven popular aquarium shapes. Click any shape to load it into the calculator above.

Tank volume vs actual water volume

A fish tank's volume is simply its length times width times height, but the actual water volume is usually 10 to 15 percent lower. Substrate, rocks and decorations displace water, and you always leave a gap at the top. For a 60 by 30 by 30 cm tank, the full volume is 54 litres, yet the real water volume is closer to 46 to 49 litres once the gravel and fill gap are accounted for. Use the full figure for buying a tank and stand, and the lower figure when dosing treatments or water conditioner.

How many gallons is my fish tank?

To find how many gallons your aquarium holds, measure the inside length, width and height, multiply them together, then convert. In inches, divide the cubic inches by 231 for US gallons or by 277.4 for UK gallons. In centimetres, divide the cubic centimetres by 3,785 for US gallons. A 76 by 33 by 46 cm tank is about 115 litres, which is roughly 30 US gallons. The calculator above works as an aquarium volume converter too, showing US gallons, UK gallons and litres at once, and the table below covers the most common aquarium sizes including the UK gallon equivalents.

Common aquarium sizes: gallons to litres

Tank size (US gallons) Litres UK gallons Typical dimensions
5 gallon 19 L 16 UK gal 41 x 21 x 25 cm
10 gallon 38 L 32 UK gal 51 x 25 x 30 cm
15 gallon 57 L 47 UK gal 61 x 30 x 30 cm
20 gallon 76 L 63 UK gal 61 x 30 x 41 cm
29 gallon 110 L 91 UK gal 76 x 33 x 46 cm
30 gallon 114 L 95 UK gal 91 x 31 x 41 cm
40 gallon 151 L 126 UK gal 91 x 46 x 43 cm
50 gallon 189 L 158 UK gal 91 x 46 x 51 cm
55 gallon 208 L 174 UK gal 122 x 33 x 53 cm
60 gallon 227 L 190 UK gal 91 x 46 x 61 cm
75 gallon 284 L 237 UK gal 122 x 46 x 53 cm
90 gallon 341 L 285 UK gal 122 x 46 x 61 cm
100 gallon 379 L 316 UK gal 183 x 46 x 51 cm
125 gallon 473 L 395 UK gal 183 x 46 x 61 cm
150 gallon 568 L 474 UK gal 183 x 46 x 76 cm
200 gallon 757 L 632 UK gal 183 x 61 x 76 cm

Fish tank size by length: how many litres?

Tank length Typical volume In gallons Typical dimensions
2 ft (60 cm) 54 L 14 US gal 60 x 30 x 30 cm
3 ft (90 cm) 110 L 29 US gal 90 x 30 x 40 cm
4 ft (120 cm) 227 L 60 US gal 120 x 38 x 50 cm
5 ft (150 cm) 450 L 119 US gal 150 x 50 x 60 cm
6 ft (180 cm) 648 L 171 US gal 180 x 60 x 60 cm

These are typical values for standard aquariums. Tanks vary by brand and glass thickness, so enter your own measurements above for the exact volume.

Fish tank dimensions to litres and gallons

Searching for the volume of an exact tank size, such as a 60 x 30 x 30 cm fish tank in litres? The table below lists the most common aquarium dimensions with their volume in litres, US gallons and UK gallons. For example, a 60 x 30 x 30 cm tank holds 54 litres, and an 80 x 30 x 40 cm tank holds 96 litres.

Tank dimensions (L x W x H) Litres US gallons UK gallons
60 x 30 x 30 cm 54 L 14 US gal 12 UK gal
60 x 30 x 38 cm 68 L 18 US gal 15 UK gal
60 x 30 x 40 cm 72 L 19 US gal 16 UK gal
80 x 30 x 40 cm 96 L 25 US gal 21 UK gal
80 x 35 x 40 cm 112 L 30 US gal 25 UK gal
90 x 30 x 40 cm 108 L 29 US gal 24 UK gal
100 x 40 x 40 cm 160 L 42 US gal 35 UK gal
100 x 40 x 50 cm 200 L 53 US gal 44 UK gal
120 x 40 x 50 cm 240 L 63 US gal 53 UK gal
120 x 50 x 50 cm 300 L 79 US gal 66 UK gal
150 x 50 x 60 cm 450 L 119 US gal 99 UK gal

How much does a full fish tank weigh?

Fresh water weighs about 1 kilogram per litre, or roughly 8.34 pounds per US gallon. So a 200 litre aquarium holds about 200 kg of water on its own, before you add the glass, stand, substrate and rocks. A filled 40 gallon (151 litre) tank weighs well over 180 kg in total. Always check that your floor and stand can support the complete filled weight, and place larger tanks against a load-bearing wall.

Surface area and how many fish you can keep

The water surface area (length times width) controls how much oxygen the tank exchanges with the air, so a wide, shallow tank supports more fish than a tall, narrow one of the same volume. A common stocking guideline is 1 cm of adult fish per 1 litre of water, or about 1 inch of fish per US gallon. By that rule, a 75 litre tank suits roughly 75 cm of small fish, for example around 25 tetras at 3 cm each. Treat this as a starting point rather than a hard limit, since filtration, fish species and adult size all matter.

Related guides

Learn the core ideas behind fish tank volume before or after using the calculator.

Calculator tools

Explore our specialised fish tank volume calculators, each tailored for a specific unit, shape or region.

In Gallons In Litres Tank Size Capacity Dimensions Water Volume Tank Weight In CM In MM In Inches In Feet Metric Hexagon Corner Cylinder & Round Bow-front Triangle Octagon Pentagon Surface Area UK Australia Substrate Stocking Glass Thickness

Frequently asked questions

How do you calculate gallons in a fish tank?
Multiply length × width × height in inches to get cubic inches, then divide by 231 for US gallons or by 277.4 for UK gallons. You can also calculate the volume in litres and multiply by 0.264 for US gallons. The calculator above does this automatically for every tank shape.
How to calculate fish tank volume?
For a rectangular tank, multiply length × width × height using the same unit for all three. Convert the result to litres by dividing cubic centimetres by 1000, or to US gallons by dividing by 3785. Other shapes use their own formula, all handled by the tool above.
How do I calculate the volume of my fish tank in litres?
Measure length, width and height in centimetres, multiply them to get cubic centimetres, then divide by 1000. For example, a 60 × 30 × 30 cm tank holds 54,000 cm³ ÷ 1000 = 54 litres.
How big is my fish tank?
Enter your tank's measurements into the calculator above and it returns the capacity in litres, US gallons and UK gallons, so you instantly know how big your tank is.
How do I calculate the size of a fish tank?
Tank size is its internal volume. Measure the inside length, width and height, multiply them together, and convert to litres or gallons. Use the fish tank size calculator above for an instant answer.
How do I calculate fish tank capacity?
Capacity is the same as the full tank volume: length × width × height for a rectangular tank. Subtract roughly 10 to 15% for substrate, rocks and the fill gap to estimate the actual water it will hold.
How do I calculate the water volume in a fish tank?
Start with the full volume (length × width × height), then subtract the space taken by substrate, rocks and decor and the gap you leave at the top. As a rule of thumb, real water volume is about 85 to 90% of the calculated capacity.
How do I calculate fish tank volume in gallons?
Work out the volume in cubic inches (length × width × height in inches) and divide by 231 for US gallons, or by 277.4 for UK gallons. The calculator shows both US and UK gallons at once.
How many gallons is my fish tank?
Enter your tank dimensions above and read the US and UK gallon figures. Remember a US gallon is 3.785 litres while a UK gallon is 4.546 litres, so the two numbers differ.
How do I calculate the volume of a hexagon or corner tank?
Select the matching shape in the calculator. Hexagon tanks use the regular-hexagon area times height; corner and quarter-cylinder tanks use a fraction of the full cylinder volume. Just enter the dimensions and the maths is done for you.
How do I work out the weight of a full fish tank?
Each litre of fresh water weighs about 1 kg (a US gallon ≈ 3.79 kg). Multiply your volume in litres by 1 kg, then add the weight of the glass, stand, substrate and rocks for the total filled weight.
What is the difference between tank volume and water volume?
Tank volume is the full internal capacity. Actual water volume is lower because substrate, rocks and decor displace water and you leave a gap at the top, usually 10 to 15% less than the calculated volume.
How do I calculate corner fish tank gallons?
A corner tank is treated as a quarter-cylinder: calculate the full cylinder volume (π × radius² × height) and divide by four, then convert to gallons. Pick "Corner bow front" or "Quarter cylinder" in the calculator.
Why does my measured volume differ from the tank's rated size?
Manufacturers usually quote the nominal outer size. Glass thickness, bracing and the fill line all reduce usable volume, so a tank rated at 200 litres often holds slightly less water in practice.
How do I calculate gallons of water in a fish tank?
Calculate the volume in cubic inches (length × width × height in inches) and divide by 231 for US gallons. For a quick estimate, find the volume in litres and multiply by 0.264.
How do I calculate the volume of a fish tank in inches or feet?
Choose 'in' or 'ft' as the unit in the calculator and enter your measurements. The tool converts automatically and returns the volume in litres and gallons.
How many litres does my fish tank hold?
Multiply length × width × height in centimetres and divide by 1000. A 80 × 35 × 40 cm tank holds 112,000 cm³ ÷ 1000 = 112 litres.
How do I calculate the volume of a cylinder or round fish tank?
Select 'Cylinder' in the calculator and enter the diameter and height. The formula used is π × (diameter ÷ 2)² × height.
Does the tank shape affect the volume?
Yes. Every shape uses a different formula, a box multiplies its three sides, while cylinders and corner tanks use π-based formulas. Pick the matching shape so the result is accurate.
How do I calculate fish tank surface area?
Surface area is the top opening of the tank: length × width for a rectangular tank. It affects gas exchange, so a wider, shallower tank holds more oxygen than a tall, narrow one of the same volume.
How many litres is a 4ft fish tank?
A standard 4ft (120 cm) aquarium is typically around 227 litres, which is about 60 US gallons, based on common dimensions of 120 x 38 x 50 cm. Exact volume depends on the width and height, so measure your tank and enter the values above for a precise figure.
How many litres is a 2ft or 3ft fish tank?
A 2ft (60 cm) tank is usually about 54 litres (14 US gallons) at 60 x 30 x 30 cm, and a 3ft (90 cm) tank is roughly 110 litres (29 US gallons) at 90 x 30 x 40 cm. These are typical sizes; use the calculator with your own measurements for the exact volume.
How many litres is a 40 gallon fish tank?
A 40 US gallon tank holds about 151 litres (40 x 3.785). A 40 UK gallon tank holds about 182 litres. Multiply US gallons by 3.785, or UK gallons by 4.546, to convert to litres.
How many gallons is my aquarium?
Measure the inside length, width and height, multiply them together, and convert: in inches divide cubic inches by 231 for US gallons, or in centimetres divide cubic centimetres by 3,785. The calculator above shows US and UK gallons instantly for any tank shape.
How do I calculate aquarium capacity?
Aquarium capacity is the full internal volume: length x width x height for a rectangular tank. Subtract about 10 to 15 percent for substrate, rocks and the fill gap to estimate the real water it will hold. Pick your shape above and the tool calculates capacity in litres and gallons.
How do I convert fish tank gallons to litres?
Multiply US gallons by 3.785 to get litres, or UK gallons by 4.546. For example, a 55 US gallon tank is about 208 litres, and a 75 US gallon tank is about 284 litres. To go the other way, divide litres by 3.785 for US gallons.
What is the formula for aquarium volume?
The aquarium volume formula for a rectangular tank is length x width x height. Use one unit for all three measurements, then divide cubic centimetres by 1,000 for litres, or cubic inches by 231 for US gallons. Cylinder and corner tanks use pi-based formulas, all built into the calculator above.
How do I work out the litres in my fish tank?
Measure the inside length, width and height in centimetres, multiply them together to get cubic centimetres, then divide by 1,000 to get litres. For example, a 90 x 30 x 40 cm tank is 108,000 cubic centimetres, which is 108 litres. Enter your measurements above to do it instantly for any shape.
How many litres is a 100 gallon fish tank?
A 100 US gallon tank holds about 379 litres, and a 100 UK gallon tank holds about 455 litres. Typical 100 gallon tank measurements are around 183 x 46 x 51 cm. Multiply US gallons by 3.785, or UK gallons by 4.546, to convert to litres.
How many litres is a 60x30x30 fish tank?
A 60 x 30 x 30 cm fish tank holds 54 litres (60 x 30 x 30 = 54,000 cubic centimetres, divided by 1,000). That is about 14 US gallons or 12 UK gallons.
How many litres is an 80x30x40 fish tank?
An 80 x 30 x 40 cm aquarium holds 96 litres (80 x 30 x 40 = 96,000 cubic centimetres, divided by 1,000), which is about 25 US gallons or 21 UK gallons.
How do I calculate fish tank sand or gravel?
Multiply tank length by width by your chosen depth, divide by 1,000 for litres, then multiply by the density (about 1.5 kg per litre for gravel, 1.6 for sand). The aquarium substrate calculator does this and shows the exact amount and weight.
Is there a goldfish tank size calculator?
Yes. Work out your tank volume in litres with the calculator above, then use the stocking calculator and the 1 cm of adult fish per litre guideline to check the tank is large enough for your goldfish.
What are common hexagon fish tank sizes?
Common hexagon aquariums are roughly 20 gallon (about 75 litres), 35 gallon (about 130 litres) and 60 gallon (about 225 litres). A 60 gallon hexagon tank is typically around 60 cm across the flat sides and about 76 cm tall. Hexagon sizes depend on the side length and height, so enter those in the hexagon calculator for the exact volume.
What are the dimensions of a 20 or 40 gallon tank in cm?
A 20 gallon (76 litre) tank is typically about 61 x 30 x 41 cm, and a 40 gallon breeder (151 litre) is about 91 x 46 x 43 cm. Dimensions vary by brand, so measure your tank and enter the values above to convert between gallons, litres and centimetres.
What is the average weight of a fish tank?
A filled freshwater tank weighs about 1 kg per litre of water, plus the glass, stand and substrate. So a typical 20 gallon (75 litre) tank weighs roughly 90 kg filled, a 40 gallon (150 litre) around 180 kg, and a 100 gallon (380 litre) well over 400 kg. Use the weight calculator for your exact tank.
What size fish tank do I need?
It depends on the fish you plan to keep. As a starting point, allow 1 cm of adult fish per litre of water: a small community of tetras suits a 60 to 100 litre tank, while goldfish or larger cichlids need much more. Work out your volume above, then use the stocking calculator to match it to your fish.
What is the volume of a hexagon or pentagon tank?
A hexagon tank's volume is the regular-hexagon area, about 2.598 times the side length squared, multiplied by the height. A pentagon tank uses about 1.720 times the side squared, times the height. Enter the side length and height in the hexagon or pentagon calculator for the exact litres and gallons.
How much does a 5 or 10 gallon fish tank weigh?
A filled 5 gallon (19 litre) tank weighs roughly 25 kg (about 55 lb), and a filled 10 gallon (38 litre) tank about 50 kg (110 lb), including the glass and a little substrate. Water alone weighs about 1 kg per litre, so use the weight calculator for your exact tank.
Is there a fish tank size chart in litres?
Yes. The tables above act as a fish tank size chart, listing common aquarium sizes from 5 gallon up to 200 gallon with each size in litres, US gallons and UK gallons, plus typical dimensions in cm. You can also enter your own measurements for any size not shown.