Aquarium Tank Volume Calculator
Calculate aquarium volume in gallons and litres from tank dimensions — rectangular, cube, cylinder, hexagonal, or bow-front shapes.
Result
- Volume19.95 gal · 75.5 L
- Raw internal volume4,608 in³
- Imperial (UK) gallons16.61 gal
- Approx. water volume (−10% for substrate/decor)17.95 gal
Step-by-step
- Volume = L × W × H = 4,608 in³.
- Convert to gallons: 4,608 in³ ÷ 231 = 19.95 US gal (and × 0.016387 = 75.5 L).
- Allow ~10% for substrate and decorations: usable water ≈ 17.95 gal.
How to use this calculator
- Choose the tank shape and whether you are measuring in inches or centimetres.
- Enter the dimensions the selected shape needs (e.g. length/width/height, or diameter for a cylinder).
- Read the volume in US gallons and litres, plus imperial gallons.
- Use the −10% figure as a realistic water volume once substrate and decor are added.
About this calculator
This calculator converts aquarium dimensions into volume in US gallons, imperial gallons, and litres, for the most common tank shapes: rectangular, cube, cylinder, regular hexagon, and bow-front. Knowing the true volume matters for stocking levels (the "one inch of fish per gallon" guideline), dosing water conditioners and medications, and sizing filters and heaters. The math is straightforward geometry — length × width × height for a rectangle, π·r²·h for a cylinder — converted using exact factors: one US gallon is defined as 231 cubic inches, and one litre is 1000 cubic centimetres. Because substrate, rocks, and decorations displace water, the tool also reports an approximate actual water volume at about 90% of the gross figure. For best accuracy, measure the inside dimensions of the glass rather than the outside.
How it works — the formula
Rectangular: V = L × W × H
Cube: V = s³
Cylinder: V = π × (d/2)² × H
Hexagon: V = (3√3/2) × s² × H
Bow-front: V ≈ (L×W + ⅔·L·bow) × H
Gallons(US) = V(in³) ÷ 231 | Litres = V(cm³) ÷ 1000Each shape uses its standard solid-geometry volume formula. The result is converted to gallons and litres with exact unit factors: 231 in³ per US gallon and 1000 cm³ per litre.
Worked examples
- Inputs:
- shape=rectangular, units=in, length=24, width=12, height=16
- Output:
- 4608 in³ ÷ 231 = 19.95 gal (75.5 L)
- Inputs:
- shape=cylinder, units=in, diameter=20, height=24
- Output:
- π·10²·24 = 7540 in³ ÷ 231 = 32.64 gal
- Inputs:
- shape=cube, units=in, length=12
- Output:
- 1728 in³ ÷ 231 = 7.48 gal
Limitations
- Uses inside dimensions ideally; outside measurements over-count by the glass thickness.
- Bow-front and hexagon results are geometric approximations of real tank shapes.
- The −10% water-volume figure is a typical allowance, not exact for your decor.
Volume estimate for stocking and dosing guidance. Verify critical dosing against measured fill volume.