Fish Tank & Aquarium Volume Calculator
How Much Water Does Your Fish Tank Hold?
Knowing the exact volume of your aquarium is one of the most useful things you can find out as a fishkeeper. Use our free calculator above to work out how many litres and gallons your tank holds, whether it's rectangular, bow front, cylinder or hexagonal.
Why Your Tank Volume Matters
- Dosing treatments and water conditioners. Most products, including water conditioners, are dosed by litres, so an accurate figure helps you avoid under- or overdosing.
- Choosing the right filter. Filters are rated for a maximum tank size, so knowing your volume makes it easy to pick one that will keep your water clean.
- Heaters and stocking. Heater wattage and the number of fish your tank can comfortably hold both depend on how much water you have.
- Choosing a stand. Water weighs around 1 kg per litre, so a large tank can be very heavy once it's full. Make sure it sits on a sturdy, purpose-built aquarium cabinet.
How to Measure Your Tank
Measure the length, depth and height in whichever unit you prefer: mm, cm, inches, feet or metres. For a bow front tank, measure the depth at both the ends and the centre. If you measure the outside of the tank, tick the glass thickness box and the calculator will work out the inside volume for you.
Remember that gravel, rocks and decorations take up space, so your actual water volume will be slightly lower. Use the "allowing for gravel & decor" figure when dosing treatments.
Need Help Choosing Equipment?
Once you know your tank volume, browse our range of aquarium filters, heaters and water treatments, or get in touch with our team for friendly, expert advice.
Got a pond? Try our Pond Volume Calculator.
Tank & Aquarium Volume Calculator
Measure your tank to find out how much water it holds, for dosing treatments, sizing filters and stocking.
How it's worked out: the inside base area of the tank is multiplied by the water height, then converted to litres (1,000 litres per cubic metre). If you measured the outside, the glass thickness is taken off each side and the base. Gravel, rocks and decor take up space, so use the lower "allowing for gravel & decor" figure when dosing treatments. The water weight doesn't include the tank, gravel or decor, so allow extra when choosing a stand.
