Tank Setup
Aquarium volume
Gallons and liters from interior inches, including bowfront, cylinder, and hex.
Tank shape
Common sizes
Results
Water volume
48.6gal
Water volume
184L
Gross (rim-full)
54.0gal
Gross (rim-full)
205L
How to use this
- Pick a tank shape (rectangular, bowfront, cylinder, half-moon, corner, hexagon, or oval).
- Use a common-size preset or enter interior dimensions in inches or centimeters.
- Set fill level and optional substrate/hardscape displacement.
- Use water volume — not rim-full gross — for medication, salt, and water-change doses.
Formulas
- Rectangular: L × W × H
- Cylinder: π × r² × H
- Half-moon: ½ × π × r × depth × H
- Corner: ¼ × π × r² × H
- Hexagon: (3√3/2) × side² × H
- Oval: π × (L/2) × (W/2) × H
- Bowfront: rectangle + half-ellipse bulge
- Water = gross × (1 − displacement) × fill ratio
Sticker gallons vs rim-full rectangle
US nicknames are marketing. Interior inches ÷ 231 is rim-full. Subtract fill gap and substrate before you dose.
| Nickname | Typical interior | Rim-full gal |
|---|---|---|
| 10 gallon | 20×10×12″ | 10.4 |
| 20 long | 30×12×12″ | 18.7 |
| 29 gallon | 30×12×18″ | 28.1 |
| 40 breeder | 36×18×16″ | 44.9 |
| 55 gallon | 48×13×21″ | 56.7 |
| 75 gallon | 48×18×21″ | 78.5 |
Worth knowing
- Manufacturer “55 gallon” labels are nominal — always measure if dosing matters.
- Save tanks in this tool so stocking and water-change calculators stay consistent.
- Bow depth is how far the curved front extends beyond a straight front pane.
Usual mistakes
- Using external glass measurements (includes glass thickness).
- Forgetting substrate and hardscape displace several gallons.
- Dosing meds from gross rim-full volume and overdosing.
See also: Water Change · Stocking · Substrate