Aquarium Volume Calculator
Aquarium volume helps estimate the water actually held after choosing an effective fill percentage. Internal dimensions are more appropriate than external glass dimensions.
How to use this calculator
- Enter internal centimetre dimensions and the percentage of gross volume expected to be water.
- Check that all inputs use the same units, period and population scope.
- Change one assumption at a time when comparing scenarios.
Formula used by aquarium volume calculator calculator
Gross litres = internal length × width × water height ÷ 1,000; effective water = gross litres × fill percentage.
- Gross litres = internal length × width × water height ÷ 1,000; effective water = gross litres × fill percentage.
- Substrate, rocks, equipment and freeboard reduce water volume. This is not advice about stocking or water chemistry.
- The tool validates inputs and rounds displayed figures for readability; it does not validate assumptions against external records.
Worked examples
Worked example
A tank 100 × 40 × 35 cm has gross volume 140 litres; at 95% effective fill it holds about 133 litres before décor displacement.
100 × 40 × 35 ÷ 1,000 × 0.95 = 133 litres.
The estimated water capacity is 133 litres.
Understanding the result
Aquarium volume helps estimate the water actually held after choosing an effective fill percentage. Internal dimensions are more appropriate than external glass dimensions.
Substrate, rocks, equipment and freeboard reduce water volume. This is not advice about stocking or water chemistry.
Important notes
Substrate, rocks, equipment and freeboard reduce water volume. This is not advice about stocking or water chemistry.
Treat the result as an estimate from the entered assumptions. For safety, legal, engineering, health or commercial decisions, verify relevant specifications and professional guidance.
Frequently asked questions
Should I use outer dimensions?
No. Glass thickness makes external dimensions overstate internal volume.
Does this tell me how many fish to keep?
No. Stocking depends on species, filtration, tank maturity and husbandry guidance.
How should I interpret this result?
Substrate, rocks, equipment and freeboard reduce water volume. This is not advice about stocking or water chemistry.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.