Aquarium Sizes: Standard Fish Tank Dimensions, Volume and Filled Weight
Outside dimensions, volume in gallons and liters, and filled weight for the standard glass tank sizes, plus metric tank sizes, how to calculate any tank's volume and what the floor and stand have to carry.
Standard US glass aquariums include the 10 gallon (about 20 × 10 × 12 in, 51 × 27 × 32 cm), the 20 long (30 × 12 × 12 in), the 29 gallon (30 × 12 × 18 in), the 55 gallon (48 × 13 × 21 in, 123 × 32 × 53 cm), the 75 gallon (48 × 18 × 21 in) and the 125 gallon (72 × 18 × 23 in). A filled tank with gravel weighs roughly 11 lb per gallon (1.3 kg per liter): about 625 lb (283 kg) for a 55 gallon.
- 10 gallon
- 20 × 10 × 12 in
- 55 gallon
- 48 × 13 × 21 in
- 55 gal filled
- ≈ 625 lb (283 kg)
- Filled weight rule
- ≈ 11 lb per gallon
On this page
Standard aquarium sizes chart
Glass tanks in the US are sold by nominal capacity, and the major makers build the common sizes to near-identical footprints so they fit the same stands and lids. The first seven rows are Aqueon's published dimensions and weights; the larger sizes are typical footprints, and their weights are estimates at 11 lb per gallon.
| Tank | Size (in) | Size (cm) | Liters | Empty | Filled |
|---|---|---|---|---|---|
| 5.5 gal | 16 × 8 × 10 | 41 × 20 × 25 | 21 L | About 6–7 lb | About 60 lb (27 kg) |
| 10 gal | 20¼ × 10½ × 12½ | 51 × 27 × 32 | 38 L | 11 lb (5 kg) | 111 lb (50 kg) |
| 20 long | 30¼ × 12½ × 12¾ | 77 × 32 × 32 | 76 L | 25 lb (11 kg) | 225 lb (102 kg) |
| 29 gal | 30¼ × 12½ × 18¾ | 77 × 32 × 48 | 110 L | 40 lb (18 kg) | 330 lb (150 kg) |
| 40 breeder | 36¼ × 18¼ × 17 | 92 × 46 × 43 | 151 L | 58 lb (26 kg) | 458 lb (208 kg) |
| 55 gal | 48¼ × 12¾ × 21 | 123 × 32 × 53 | 208 L | 78 lb (35 kg) | 625 lb (283 kg) |
| 75 gal | 48½ × 18½ × 21⅛ | 123 × 47 × 54 | 284 L | 98 lb (44 kg) | 785 lb (356 kg) |
| 90 gal | 48 × 18 × 24 | 122 × 46 × 61 | 341 L | Varies by maker | About 1,000 lb (450 kg) |
| 125 gal | 72½ × 18½ × 23⅛ | 184 × 47 × 59 | 473 L | 177 lb (80 kg) | 1,400 lb (635 kg) |
| 150 gal | 72 × 18 × 28 | 183 × 46 × 71 | 568 L | Varies by maker | About 1,650 lb (750 kg) |
| 180 gal | 72 × 24 × 25 | 183 × 61 × 64 | 681 L | Varies by maker | About 2,000 lb (900 kg) |
Other common US sizes share these footprints: the 15 gallon (24 × 12 × 12 in) and 20 high (24 × 12 × 17 in) sit on a 24 × 12 in base, and the 40 long (48 × 13 × 17 in) uses the 55 gallon's footprint at a lower height. Rimless tanks and all-in-one kits are built to their own sizes, so check the spec sheet.
Metric aquarium sizes
Outside North America, tanks are usually named by length in centimeters or by volume in liters. Common sizes, with gross volume calculated from the outside dimensions:
| Size (cm) | Size (in) | Gross volume | US gallons |
|---|---|---|---|
| 40 × 25 × 25 | 15.7 × 9.8 × 9.8 | 25 L | 6.6 |
| 60 × 30 × 30 | 23.6 × 11.8 × 11.8 | 54 L | 14.3 |
| 60 × 30 × 36 | 23.6 × 11.8 × 14.2 | 65 L | 17.1 |
| 80 × 35 × 40 | 31.5 × 13.8 × 15.7 | 112 L | 29.6 |
| 100 × 40 × 50 | 39.4 × 15.7 × 19.7 | 200 L | 52.8 |
| 120 × 40 × 50 | 47.2 × 15.7 × 19.7 | 240 L | 63.4 |
| 150 × 50 × 60 | 59.1 × 19.7 × 23.6 | 450 L | 118.9 |
European makers often quote net water volume, which is 10–20% less than the gross figure once glass thickness, substrate and the gap below the rim are counted. When comparing a "240 L" tank with a US 55 gallon (208 L), check whether both figures are gross.
How to calculate a tank's volume and weight
- Measure inside length, width and water depth, in inches or centimeters.
- Gallons = L × W × H (in) ÷ 231. Liters = L × W × H (cm) ÷ 1,000. Example: 48 × 12 × 20 in of water ÷ 231 = 49.9 gallons (189 L).
- Water weight: 8.34 lb per US gallon, or 1 kg per liter (saltwater is about 2.5% heavier).
- Total weight: add the empty tank, substrate (gravel or sand weighs about 90–100 lb per cu ft, so 2 in across a 48 × 13 in floor adds about 65–70 lb, or 30–32 kg) and rock. A total of 10–12 lb per nominal gallon is a reliable planning figure.
Residential floors in the US are designed for a uniformly distributed live load of 40 lb per sq ft (IRC Table R301.5). A filled 75 gallon tank puts about 785 lb on 6.2 sq ft, roughly 125 lb per sq ft, before the stand. Floors usually carry a 55–75 gallon tank safely when it sits against a load-bearing wall and runs across the joists, not parallel between two. For 125 gallons and up, upper floors or older houses, ask a structural engineer or a builder to check the joists.
Stands and furniture
A stand must support the whole perimeter of the tank's bottom frame and be exactly level. A top that flexes or is out of level puts uneven stress on the bottom seams and can cause leaks.
- Matching footprint: the stand top should match the tank footprint or exceed it by no more than about 1 in (2.5 cm) on each side. A 55 gallon needs a 48 × 13 in stand; a 75 gallon a 48 × 18 in stand.
- Furniture: dressers and TV stands are rarely built for 300–800 lb concentrated on their top. A 10 or 20 gallon tank is usually fine on sturdy furniture with a solid top; larger tanks need a purpose-built stand. Compare footprints with dresser dimensions and TV stand sizes if you plan to use one, and check the maker's load rating.
- Bookcases: shelves are not designed for concentrated loads. Keep them to nano tanks of a few gallons, within the maker's shelf rating; see bookcase dimensions.
- Viewing height: most stands are 28–32 in (71–81 cm) tall, which puts the middle of a 21 in tank at about eye level for a seated adult.
Choosing a tank size
Size the tank to the adult size and behavior of the fish, not their size in the store, and remember footprint matters as much as volume.
- Length: active swimmers such as danios and rainbowfish need length; a 48 in tank gives 2.4 times the swimming run of a 20 in tank, and a 72 in tank 3.6 times.
- Depth front to back: 18 in (46 cm) tanks such as the 40 breeder and 75 gallon give room for rockwork and plants. 12–13 in deep tanks look cramped once decor is in.
- Height: taller tanks are harder to reach into. Anything over about 24 in deep needs long tools and arms, and lighting must be stronger to reach plants at the bottom.
- Getting it in: a 72 in tank in its box will not turn through some hallways. Check door and hall widths in the door size guide, and plan enough helpers: an empty 125 gallon tank weighs 177 lb (80 kg). Room layouts are easier with the furniture dimensions guide, and a water-resistant mat or rug under the stand protects the floor from drips.
Frequently asked questions
What are the dimensions of a 20 gallon tank?
There are two. A 20 long is about 30 × 12.5 × 12.75 in (77 × 32 × 32 cm), and a 20 high is about 24 × 12.5 × 16.75 in (62 × 32 × 43 cm). The long version has more floor area, which suits bottom-dwelling fish and gives more surface for gas exchange.
How much does a 75 gallon aquarium weigh when full?
About 785 lb (356 kg) filled with water, substrate and decor, according to Aqueon's chart for its 48.5 × 18.5 × 21 in tank. The empty glass tank weighs about 98 lb (44 kg). Add the stand, often 50–150 lb more.
How do I calculate the gallons in a fish tank?
Multiply length × width × height in inches and divide by 231 for US gallons. For liters, multiply the dimensions in centimeters and divide by 1,000. Use inside measurements and the actual water depth: a tank filled to 1 in below the rim with 2 in of gravel holds about 10–15% less water than its nominal size.
What is the difference between a 40 breeder and a 40 long?
The 40 breeder is 36 × 18 × 17 in (92 × 46 × 43 cm), short and deep front to back. The 40 long is about 48 × 13 × 17 in (123 × 32 × 43 cm), longer and narrower. The breeder's 18 in depth gives more room for aquascaping and fits a 36 in stand.
What size tank for a beginner?
A 20 long or a 29 gallon is a common starting size: large enough that water quality changes slowly, small enough to fit a standard 30 in stand and to move. Tanks under 10 gallons are harder to keep stable, not easier.