How aquarium weight is calculated
The total is the sum of everything on the stand:
Water is the heavy part: 1 kg per litre, or 8.34 lb per US gallon. Salt water weighs about 2.5% more (8.55 lb per gallon).
The empty tank is worked out from its five glass panels. Glass weighs 2.5 kg for every litre of glass (156 lb per cubic foot); acrylic weighs less than half as much. If you do not know your glass thickness, the calculator estimates what a factory-built tank of that size would use.
Worked example. A 55-gallon tank (48 × 13 × 21 in), set up:
| Part | Weight |
|---|---|
| Water, about 52 gallons | 435 lb (197 kg) |
| Empty glass tank | 70 lb (32 kg) |
| Gravel and rocks | 80 lb (36 kg) |
| Stand, hood, filter, light | 80 lb (36 kg) |
| Total | about 665 lb (300 kg) |
A useful rule of thumb: a set-up glass aquarium weighs 10 to 12 lb per US gallon (1.2 to 1.5 kg per litre) of its nominal size, stand included.
Will my floor hold it?
A concrete ground floor will carry any home aquarium. Timber floors need more thought as tanks get bigger.
- Up to about 55 gallons (200 L): fine on almost any sound floor, on a proper aquarium stand.
- 55 to 125 gallons (200–475 L): place the tank against a load-bearing wall, with its length running across the floor joists so the weight is shared by several of them, not sitting on one or two.
- Over 125 gallons (475 L), or any large tank upstairs: ask a structural engineer or experienced builder before filling it. The answer depends on joist size, span and spacing, which no online calculator can see.
The "load on the floor" figure spreads the weight over the tank's footprint. It lets you compare tanks, but floors are not rated by a single number: a long tank across many joists is carried more easily than a short, tall one of the same weight.
The stand matters as much as the floor
Use a stand built for aquariums. Ordinary furniture is designed for a fraction of this load and sags over time, and particleboard swells and fails once it gets wet. The stand must be level and must support the tank's whole bottom frame or, for rimless tanks, the whole base on a foam mat. An uneven stand twists the glass and is the most common cause of cracked tanks and failed seams.
Common mistakes
- Putting a tank on a dresser, desk or bookshelf. They are not built for hundreds of pounds, or for water.
- Moving a tank with water in it. Even a few centimetres of water can twist and crack the glass. Empty it fully.
- Running the tank along the joists. On timber floors, place it across the joists and near a wall.
- Ignoring a stand that rocks. Shim the stand, never the tank, until it is level in both directions.
Questions and answers
How much does a 55 gallon fish tank weigh full?
About 625–665 lb (285–300 kg) with water, gravel and decor, and around 700 lb (320 kg) including a stand. The empty glass tank weighs about 70–78 lb (32–35 kg).
How much does a 20 gallon tank weigh?
A filled 20-gallon aquarium weighs about 225 lb (102 kg). Empty, it weighs about 25 lb (11 kg).
How much does a 10 gallon tank weigh when full?
About 110 lb (50 kg), of which the water is about 80 lb. The empty tank weighs about 11 lb (5 kg).
How heavy is a 75 gallon aquarium?
About 850 lb (385 kg) filled, plus the stand. Empty, about 140 lb (64 kg).
Can my floor support a 125 gallon aquarium?
A 125-gallon tank weighs around 1,400 lb (635 kg) filled. On a concrete floor that is fine. On a timber floor it should sit across the joists against a load-bearing wall, and it is wise to have the floor checked first.
How much does a gallon of water weigh?
A US gallon of fresh water weighs 8.34 lb (3.78 kg). A UK gallon weighs 10 lb (4.54 kg). A litre weighs 1 kg.
Related guides
Sources
- Density of float glass 2,500 kg/m³; acrylic 1,190 kg/m³; fresh water 998 kg/m³ at 24 °C; sea water about 1,025 kg/m³.