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Aquarium Water Weight Calculator

Work out how much the water in a fish tank weighs so you can check your stand and floor.

✔ Reviewed by our vet teamUpdated 18 Oct 2026Sources: Pure arithmetic / unit conversion on user inputs
Aquarium Water Weight CalculatorFree · instant
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Quick answer A 200 litre tank holds about 200 kg of water, roughly 441 lb, because a litre of water weighs about a kilogram. Glass, gravel, rocks and the stand add more, so check the stand's rated load and your floor before filling a large tank.

How to use the aquarium water weight calculator

  1. Enter the volume of water in the tank, and tick saltwater if it is a marine tank.
  2. Add the weight of gravel or sand and the empty tank weight from the maker if you know them.
  3. Press Calculate to see the filled weight to compare with your stand's rated load.

Worked example

A tank holding 200 litres of water.

Tank volume (water)
200 L
200 kg (441 lb)
Water volume
200 L (53 US gal)
Water weight
200 kg (441 lb)

Water only unless you added the other weights. Glass, stand, rocks and equipment add more, so enter the empty tank weight from the maker and check your stand's rated load.

Example values are illustrative; this result is produced by the same calculator above.

How we calculate it

Water weight = litres × 1 kg per litre (freshwater) or × 1.025 (typical marine specific gravity). Total = water + substrate + empty tank and equipment weight, each as entered.

Sources: Pure arithmetic / unit conversion on user inputs (no external constant)

Understanding your result

Water is heavy: a litre weighs about a kilogram, so a 200 litre tank holds about 200 kg of water, roughly 441 lb. A US gallon weighs about 8.3 lb.

The calculator converts the water volume you enter into kilograms, pounds and tonnes. Use the Aquarium Volume Calculator first if you only know the tank's measurements.

The figure is the water only. Glass, the stand, gravel, rocks, wood and equipment add more, so check the manufacturer's filled weight and the stand's rated load before filling a large tank.

Common mistakes

  • Forgetting the weight of the tank, gravel and decorations.
  • Using the empty-tank volume instead of the water volume.
  • Putting a large tank on furniture that is not built for the load.
  • Ignoring the floor: weight per area matters as well as total weight.
  • Mixing litres and gallons.

Good to know

  • Placing a heavy tank along a load-bearing wall or on the ground floor is safer.
  • Ask the tank or stand maker for the maximum load.
  • If you are unsure about your floor, ask a builder or surveyor.

Frequently asked questions

How much does a gallon of water weigh?

One US gallon of water weighs about 8.3 pounds (3.79 kg), because one litre of water weighs about one kilogram.

Does this include the tank itself?

No. Glass, the stand, gravel, rocks, equipment and decorations all add weight, so check the tank maker's total filled weight and your stand's rated load.

Why does it matter?

Large tanks are very heavy and floors and stands have limits. If in doubt ask the manufacturer or a builder.

Does this include the glass and the stand?

Only if you enter the empty tank weight from the maker. Glass and equipment can add a lot, so check the filled weight and the rated load of your stand before you fill the tank.

How do I get the water volume?

Use the Aquarium Volume Calculator, then subtract a little for gravel and decorations if you want a closer figure.

Is the water the heaviest part?

In most tanks yes, but glass, gravel, rocks and equipment can add a lot, especially in large tanks.

Where should I put a large tank?

On a stand rated for the load, ideally along a load-bearing wall or on a ground floor. Ask a builder if you are unsure.

Reviewed by the CalcuPaw Veterinary Review Team
Reviewed 8 Oct 2026 to 18 Oct 2026 · next review due by April 2027 · Meet the review team

Sources

  1. Pure arithmetic / unit conversion on user inputs (no external constant)

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Estimates only. Every pet is different — confirm with your veterinarian.