Aquarium tank sizes chart: dimensions, gallons, litres and weight
Standard glass aquariums come in a handful of sizes. Here they all are with their usual dimensions, how many US gallons and litres they hold, and how much the water weighs on your stand.
By ScapeMath · Updated · Every number on this page is computed with the same formulas as our calculators.
Want the exact figure for your tank? Measure the inside of your glass and the calculator gives litres, US and UK gallons, real water volume and weight for rectangle, bow-front, corner, hexagon and cylinder tanks. Open the free aquarium volume calculator.
Fish tank sizes chart
Nominal dimensions are the size class makers sell tanks by. Volumes and weights below are for a tank filled to the brim with fresh water at 25 °C (77 °F), or 35 ppt saltwater. Your real water volume is lower, as explained below. Aqueon's own listed outside dimensions are shown for comparison: they include the plastic trim, so they run a fraction of an inch bigger.
| Tank | L × W × H (in) | L × W × H (cm) | US gal | Litres | Water weight, fresh | Saltwater | Aqueon outside (in) |
|---|---|---|---|---|---|---|---|
| 2.5 gallon | 12 × 6 × 8 | 30 × 15 × 20 | 2.5 | 9 | 21 lb (9 kg) | 21 lb | 12.25 × 6.25 × 8.125 |
| 5.5 gallon | 16 × 8 × 10 | 41 × 20 × 25 | 5.5 | 21 | 46 lb (21 kg) | 47 lb | 16.25 × 8.375 × 10.5 |
| 10 gallon | 20 × 10 × 12 | 51 × 25 × 30 | 10.4 | 39 | 86 lb (39 kg) | 89 lb | 20.25 × 10.5 × 12.625 |
| 15 gallon | 24 × 12 × 12 | 61 × 30 × 30 | 15.0 | 57 | 124 lb (56 kg) | 128 lb | 24.25 × 12.5 × 12.75 |
| 20 gallon long | 30 × 12 × 12 | 76 × 30 × 30 | 18.7 | 71 | 156 lb (71 kg) | 160 lb | 30.25 × 12.5 × 12.75 |
| 20 gallon high | 24 × 12 × 16 | 61 × 30 × 41 | 19.9 | 76 | 166 lb (75 kg) | 170 lb | 24.25 × 12.5 × 16.75 |
| 29 gallon | 30 × 12 × 18 | 76 × 30 × 46 | 28.1 | 106 | 233 lb (106 kg) | 240 lb | 30.25 × 12.5 × 18.75 |
| 40 gallon breeder | 36 × 18 × 16 | 91 × 46 × 41 | 44.9 | 170 | 373 lb (169 kg) | 383 lb | 36.25 × 18.25 × 17 |
| 55 gallon | 48 × 13 × 21 | 122 × 33 × 53 | 56.7 | 215 | 472 lb (214 kg) | 484 lb | 48.25 × 12.75 × 21 |
| 60 gallon breeder | 48 × 18 × 16 | 122 × 46 × 41 | 59.8 | 227 | 498 lb (226 kg) | 511 lb | 48.5 × 18.5 × 16 |
| 75 gallon | 48 × 18 × 21 | 122 × 46 × 53 | 78.5 | 297 | 654 lb (296 kg) | 671 lb | 48.5 × 18.5 × 21.125 |
| 90 gallon | 48 × 18 × 24 | 122 × 46 × 61 | 89.8 | 340 | 747 lb (339 kg) | 767 lb | 48.5 × 18.5 × 25.125 |
| 120 gallon | 48 × 24 × 24 | 122 × 61 × 61 | 119.7 | 453 | 996 lb (452 kg) | 1,022 lb | – |
| 125 gallon | 72 × 18 × 21 | 183 × 46 × 53 | 117.8 | 446 | 980 lb (445 kg) | 1,006 lb | 72.5 × 18.5 × 23.125 |
How many gallons is my tank really?
To the brim, a tank's volume is L × W × H ÷ 231 in US gallons. In use you lose some of that: the water sits an inch or two below the rim, and sand and rock take up space. The figures below assume water 1 in below the rim over a 2 in sand bed that displaces 60% of its own volume (loose sand is about 40% water-filled pore space).
How many gallons is a 20 long?
30 × 12 × 12 in = 4,320 in³ ÷ 231 = 18.7 US gallons (70.8 L). At a normal fill over sand: about 15.3 US gallons (58 L).
How many gallons is a 29 gallon tank?
30 × 12 × 18 in = 6,480 in³ ÷ 231 = 28.1 US gallons (106.2 L). At a normal fill over sand: about 24.6 US gallons (93 L). The 29 shares its 30 × 12 in footprint with the 20 long.
How many gallons is a 40 breeder?
36 × 18 × 16 in = 10,368 in³ ÷ 231 = 44.9 US gallons (169.9 L). At a normal fill over sand: about 38.7 US gallons (147 L). The extra depth front to back is why it holds more than its "40" with such a short height.
How many gallons is a 55 gallon?
48 × 13 × 21 in = 13,104 in³ ÷ 231 = 56.7 US gallons (214.7 L). At a normal fill over sand: about 50.8 US gallons (192 L). A 55 is narrow (13 in front to back), so it holds a lot of water for its footprint.
How many gallons is a 75 gallon?
48 × 18 × 21 in = 18,144 in³ ÷ 231 = 78.5 US gallons (297.3 L). At a normal fill over sand: about 70.3 US gallons (266 L). It has the same 48 in length as a 55 but 18 in depth, so it takes a wider stand.
Metric (rimless) tank sizes in litres
Rimless and European tanks are usually sold in centimetres. Litres are simply L × W × H ÷ 1,000.
| Tank | Litres | US gal | UK gal | Water weight |
|---|---|---|---|---|
| 30 × 30 × 30 cm | 27.0 | 7.1 | 5.9 | 27 kg |
| 45 × 30 × 30 cm | 40.5 | 10.7 | 8.9 | 40 kg |
| 60 × 30 × 36 cm | 64.8 | 17.1 | 14.3 | 65 kg |
| 60 × 45 × 45 cm | 121.5 | 32.1 | 26.7 | 121 kg |
| 90 × 45 × 45 cm | 182.3 | 48.1 | 40.1 | 182 kg |
| 120 × 45 × 45 cm | 243.0 | 64.2 | 53.5 | 242 kg |
| 120 × 60 × 60 cm | 432.0 | 114.1 | 95.0 | 431 kg |
How much does a full aquarium weigh?
Fresh water weighs about 8.3 lb per US gallon (0.997 kg per litre at 25 °C) and 35 ppt saltwater about 8.5 lb. But a full tank is more than water. Take a 55 gallon with 1/4 in glass:
- Water: about 51 US gallons at a normal fill, 423 lb (192 kg).
- Glass: five panels, 3,186 in² at 1/4 in thick, at about 2.5 kg/L for glass: 72 lb (33 kg).
- Sand: a 2 in bed of aragonite sand (CaribSea's 100 lb/ft³): 72 lb (33 kg).
That's roughly 567 lb (257 kg) before rock, the lid, lights and the stand itself. Check the maker's load rating for your stand and floor, and put big tanks across floor joists or near a load-bearing wall. Size the bed for your tank with the substrate calculator and the substrate chart.
How to measure your tank
- Measure the inside length, width (front to back) and water depth. Inside dimensions skip the glass and trim.
- If you only have outside dimensions, subtract twice the glass thickness from the length and width, and the bottom glass from the height.
- Multiply. In inches, divide by 231 for US gallons. In centimetres, divide by 1,000 for litres.
Bow-front, corner, hexagon and cylinder tanks need their own formulas, and the aquarium volume calculator handles all of them.
Common questions
How many gallons is a 20 long?
A standard 20 long is 30 × 12 × 12 in, which is 18.7 US gallons (70.8 L) filled to the brim. With the water an inch below the rim over a 2 in sand bed it holds about 15.3 US gallons (58 L).
How many litres is a 55 gallon tank?
A 48 × 13 × 21 in 55 gallon is 215 L (56.7 US gallons) to the brim, or about 192 L of water at a normal waterline over a 2 in sand bed.
What are the dimensions of a 40 gallon breeder?
36 × 18 × 16 in (91 × 46 × 41 cm) nominal; Aqueon lists its 40 breeder at 36.25 × 18.25 × 17 in outside. That holds 44.9 US gallons (169.9 L), and its 18 in depth makes it popular for aquascapes and breeding.
How much does a 75 gallon aquarium weigh full?
The water alone is about 654 lb (296 kg) fresh or 671 lb as saltwater, filled to the brim. A 2 in bed of aragonite sand adds 100 lb, and the glass and stand come on top.
What is the difference between a 20 high and a 20 long?
The 20 high is 24 × 12 × 16 in and holds 19.9 US gallons; the 20 long is 30 × 12 × 12 in and holds 18.7. The long has a 25% bigger footprint (360 vs 288 in²), which means more swimming length, more substrate and more surface area.
Is a 29 gallon the same size as a 20 long?
Same footprint, taller tank. Both are 30 × 12 in at the base, but the 29 gallon is 18 in tall instead of 12, so it holds 28.1 US gallons against 18.7. They take the same stand and the same amount of substrate.
References
- NIST Handbook 44, Appendix C: General tables of units of measurement (US gallon = 231 in³ = 3.785411784 L; inch = 2.54 cm)
- Aquarium Dimensions catalog: Aqueon standard glass aquariums (listed outside dimensions)
- Millero, F.J. & Poisson, A. (1981). International one-atmosphere equation of state of seawater. Deep-Sea Research 28A: 625–629 (water and seawater density)
- CaribSea, Inc. FAQ: "How many pounds do I need?" (aragonite sand 100 lb/ft³)
- Engineering ToolBox: Densities of solids (glass, about 2,400–2,800 kg/m³)
The tables on this page are generated from the calculators' own code and checked by automated tests. Last reviewed November 3, 2026. Found an error? Tell us.
Calculators for this job
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How many gallons or litres your tank holds: rectangular, cylinder, bow-front, corner and hexagon, plus water weight.
Substrate: sand, gravel & aquasoil
How many pounds or kilograms of sand or gravel, or litres of aquasoil, for a flat or sloped bed, and how many bags to buy.
Heater wattage
How many watts your tank needs, from volume, room and target temperature, and optional evaporation.
Water change & dilution
What a water change does to nitrate, salinity or hardness, how much to change to hit a target, and RO/tap blends.
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