Cube Tank Volume
edge³ ÷ 231. Enter your measurements for gallons and liters.
Volume
28.05 gal
Liters
106.2 L
This is the full water volume; actual capacity is a bit lower once you add substrate, rocks and the fill line.
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The cube formula
Volume in US gallons is edge³ ÷ 231, with every measurement in inches. The 231 is fixed: a US gallon is exactly 231 cubic inches, so cubic inches divided by 231 is gallons, and gallons × 3.785 is liters.
Measuring it without inflating the number
Measure one inside edge. If the tank is not perfectly square (many are an inch off in depth), measure all three and use the rectangular formula instead.
What this shape does to your stocking limit
A cube packs the most water into the smallest footprint, so it suits a side table or a nano setup. The cost is depth front to back, which makes aquascaping harder to light evenly and reduces swimming length for active fish.
Standard sizes in this shape family
Nominal gallons and the real footprint they ship with.
- 5 gallon tank16" × 8" × 10.5"
- 10 gallon tank20" × 10" × 12"
- 20 gallon tank24" × 12" × 16"
- 29 gallon tank30" × 12" × 18"
- 40 gallon tank36" × 18" × 16"
- 55 gallon tank48" × 13" × 21"
- 75 gallon tank48" × 18" × 21"
- 90 gallon tank48" × 18" × 24"
- 125 gallon tank72" × 18" × 21"
Volume by tank shape
- Rectangular tankslength × width × height ÷ 231
- Cylinder tanksπ × (diameter ÷ 2)² × height ÷ 231
- Bowfront tankslength × width × height × 1.06 ÷ 231
- Hexagonal tanks(3√3 ÷ 2) × edge² × height ÷ 231
What to do with the number
- What bioload actually isGallons is the denominator, not the answer
- Cycle the tank firstFishless cycling, step by step
Frequently asked questions
How do you calculate the volume of a cube tank?
edge³ ÷ 231, with every dimension in inches. Dividing cubic inches by 231 gives US gallons.
How do I measure a cube tank correctly?
Measure one inside edge. If the tank is not perfectly square (many are an inch off in depth), measure all three and use the rectangular formula instead.
Does tank shape change how many fish I can keep?
A cube packs the most water into the smallest footprint, so it suits a side table or a nano setup. The cost is depth front to back, which makes aquascaping harder to light evenly and reduces swimming length for active fish.
Keep going with the same pet
Got your gallons? Check how many fish that really supports.
Your dog's age in human years, breed-size adjusted, not the ×7 myth.
Your cat's age in human years using the real feline curve, not the ×7 myth.
How much to feed: daily calories and cups by weight, activity and life stage.
Bioload-based stocking guidance, not the oversimplified 1-inch-per-gallon rule.