Tank Volume Calculator
Tank Volume Calculator finds your exact aquarium capacity in litres and gallons — enter dimensions for rectangular or bowfront tanks, with optional substrate depth.
Calculator
Unit
Shape
Measure internal dimensions for accuracy
Waiting for tank dimensions
Enter your tank's length, width, and height to calculate its volume.
Gear that works with your tank size
Selected for planted tanks of all sizes.
Volcanic substrate granules — promotes slightly acidic pH ideal for most aquatic plants and shrimp
Hand-selected natural hardscape — adds structure and a surface for moss and epiphytes to attach
Natural stone for hardscape — creates focal points and visual depth in planted layouts
I’ve used everything listed in my own tanks. If you buy through a link, I earn a small commission — at no extra cost to you, and it never affects what I recommend.
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Frequently Asked Questions
- How do I measure my aquarium volume accurately?
- Always measure internal dimensions, not external. The glass thickness (typically 6–12 mm on standard tanks) reduces the usable water volume. Use a tape measure inside the tank for the most accurate reading.
- What's the difference between US and UK gallons?
- A US gallon equals approximately 3.785 litres, while a UK (Imperial) gallon equals 4.546 litres — about 20% larger. Most aquarium equipment sold in the UK and Europe is labelled in litres, while US products use US gallons. If you are shopping online from the US, always verify whether flow rates or volumes are given in US gallons before comparing with metric-labelled equipment.
- How much substrate do I need for a planted tank?
- A depth of 5–8 cm (2–3 inches) is standard for most planted aquascapes. Foreground areas can be shallower (3–4 cm) while background planting benefits from 8–10 cm. Use the substrate depth input above to see how much volume your chosen depth displaces.
- Does tank shape affect the volume?
- Yes. Bowfront tanks have a curved front pane that adds roughly 10–15% more volume than a rectangular tank of the same footprint. This calculator applies a 12% adjustment for bowfront shapes, which is a reasonable average — exact figures vary by manufacturer.
- Why is net volume different from gross volume?
- Gross volume is the total internal capacity. Net volume subtracts the space taken up by substrate, decorations, and equipment. For a planted tank with substrate, the net volume is the approximate amount of water you'll actually be adding — useful for calculating fertiliser doses and water change volumes.