Aquarium weight calculator

Typical fish tank weights

Weights for common standard tanks. Empty weights are our estimates for the glass alone, using the typical thicknesses further down this page. Real tanks vary by maker, so check the label on yours if you need an exact figure.

"Water + tank" uses the full nominal size, for example 55 gallons × 8.34 lb. "Set up" is this calculator's estimate with 2 in of gravel and the water 1 in below the top. It can be higher or lower: gravel adds weight, but the glass, the gap at the top and the gravel itself take up space that would otherwise hold water. When you choose a stand, the higher of the two gives you a margin.

How the calculator works

The calculator adds up five things: water, glass, substrate, rock and decor, and any equipment you enter. All sizes are the outside measurements of the tank, and the glass thickness is t.

1. Glass. Bottom (L × W) + front and back (2 × L × (H − t)) + two ends (2 × (W − 2t) × (H − t)), each multiplied by t. That gives the volume of glass without counting the edges twice. Glass weighs 2.5 kg per litre (2.5 g/cm³).
2. Substrate. Inside length × inside width × depth × the weight of a litre of that substrate: gravel 1.6 kg/L, sand 1.55 kg/L and aquasoil about 1.0 kg/L. Aquasoil brands vary, so check the weight and volume on your bag.
3. Water. Inside length (L − 2t) × inside width (W − 2t) × water depth (H − t − the gap at the top), minus the space taken by the stone in the substrate and rock. Stone is about 2.65 kg per litre, so every 2.65 kg of gravel or rock pushes out 1 litre of water. Water weighs 8.34 lb per US gallon, which is 0.9994 kg per litre.
4. Total. Water + glass + substrate + rock and decor + equipment. This is what your stand has to hold.
5. Floor load. (Total + stand) ÷ footprint (L × W). We assume the stand has the same footprint as the tank.

Worked example: a 55 gallon tank

A standard 55 gallon tank is 48 × 13 × 21 in outside. Say it has typical 1/4 in (6.4 mm) glass, 2 in of gravel and the water 1 in below the top.

• Glass: 624 + 1,992 + 518.75 = 3,134.75 in² × 0.25 in = 783.7 in³ (12.84 L). × 2.5 kg/L = 32.1 kg (70.8 lb).
• Gravel: 47.5 × 12.5 × 2 in = 1,187.5 in³ (19.46 L). × 1.6 kg/L = 31.1 kg (68.6 lb).
• Water: 47.5 × 12.5 × 19.75 in = 11,726.6 in³, which is 50.8 gal (192.2 L). The gravel's stone takes up 31.1 ÷ 2.65 = 11.7 L, leaving 180.4 L (47.7 gal) of water = 180.3 kg (397.5 lb).
• Total: 397.5 + 70.8 + 68.6 = 537 lb (244 kg), or about 9.8 lb per nominal gallon.
• Floor load: the footprint is 48 × 13 in = 4.33 ft² (0.403 m²), so 537 ÷ 4.33 = 124 lb/ft² (605 kg/m²), before adding the stand.

Notice the water: a "55 gallon" tank holds about 47.7 gallons once it is set up. Tank sizes are named from the outside measurements, so the glass, the gap at the top and the gravel all take some away.

Typical glass thickness by tank size

If you choose "Typical for this size", the calculator picks the glass from this table using the tank's outside volume. Tanks taller than 24 in (61 cm) move up one step, because water pressure on the glass rises with depth. These are typical for standard framed glass tanks. Rimless tanks often use thicker glass, and acrylic tanks are much lighter than glass, so enter your own thickness if you know it.

Choosing a stand

• Rated for the full weight. Use the total from the calculator, including gravel, rock and equipment, and pick a stand made for aquariums and rated for at least that much.
• Flat and level. The tank must sit evenly. A stand that rocks or a top that sags puts stress on the glass and the seams. Check it with a spirit level before you fill the tank.
• Supports the right places. Framed tanks are built to rest on their bottom frame. Rimless tanks usually need a flat, fully supported surface, often with a thin mat; follow the maker's instructions.
• Furniture is risky. Dressers, desks and bookcases are rarely rated for a filled tank. Even a 20 gallon is about 190 lb with water.
• Never move a full tank. Drain it first. Wet gravel alone can weigh more than the glass, and lifting a part-filled tank strains the seams.

Is your floor strong enough?

We can't tell you whether a particular floor is safe, but these general points help:

• Floor load is weight divided by the area under the stand. A typical 55 gallon setup puts about 124 lb/ft² (605 kg/m²) on its footprint.
• For comparison, US homes built to the International Residential Code are designed for a live load of 40 lb/ft² (about 195 kg/m²) in living areas and 30 lb/ft² in bedrooms. That figure is spread over the whole room, while a tank concentrates its weight on a small patch that the joists share, so the two numbers are not directly comparable. The gap is still the reason heavy tanks deserve care.
• Place heavy tanks against a wall, ideally a load-bearing one, with the long side running across the floor joists so more joists share the weight.
• A ground floor on a concrete slab is the easiest place for a big tank.
• If the total is over about 1,000 lb (454 kg), or the tank is going upstairs, into an older home or onto a floor that bounces or sags, ask a builder or structural engineer before you fill it.

Related tools

• Aquarium volume calculator: Work out how many gallons or litres your tank holds, for rectangular, cylinder, bow front, corner and hexagon tanks.
• Aquarium gravel and sand calculator: Find how many pounds or kilograms of gravel, sand or aquasoil you need for the depth you want.
• Aquarium heater size calculator: Find the right heater wattage for your tank size, room temperature and target water temperature.
• Aquarium filter flow rate calculator: See what filter flow rate (GPH or L/h) your tank needs, and check whether your current filter is enough.
• Water change and nitrate calculator: See how much a water change lowers nitrate, and how many changes it takes to reach a target.
• Aquarium CO2 calculator (pH and KH): Estimate dissolved CO2 in a planted tank from your pH and KH readings.
• Aquarium unit converter: Convert gallons and litres, Fahrenheit and Celsius, inches and centimetres, and dGH, dKH and ppm.
• Fish tank stocking calculator: check how many fish your tank can hold, and whether they get along.
• Fish tank sizes: dimensions, volumes and fish ideas for common tank sizes.
• Fishkeeping guides: setting up, cycling and looking after a tank.

Sources

• USGS Water Science School, Water density: fresh water is densest, 1.000 g/cm³, at 4 °C.
• Engineering ToolBox, Water density and specific weight: 997 kg/m³ (8.32 lb per US gallon) at 25 °C.
• Wikipedia, Soda–lime glass: flat (window) glass about 2.5 g/cm³.
• CaribSea, Freshwater substrates: aquarium gravels list an average density of about 96–100 lb/ft³ (1.54–1.6 kg/L). The same figures are used by our gravel and sand calculator.
• Engineering ToolBox, Dirt and mud densities: dry sand 1,555 kg/m³ (1.55 kg/L).
• Engineering ToolBox, Densities of solids: quartz 2,650 kg/m³, granite 2,600–2,800 kg/m³.
• International Code Council, 2021 International Residential Code, Table R301.5: minimum floor live loads.
• NIST, Guide for the Use of the SI (SP 811): conversion factors (1 lb = 0.45359237 kg; 1 US gallon = 3.785 L).