20 Gallon High Tank: Dimensions, Volume & Weight
A standard 20 Gallon High aquarium measures about 24 x 12 x 16 in (61 x 30.5 x 40.6 cm) and holds 75.7 L (20 US gal) at its full nominal rating. At a typical 90% fill with 15 L of substrate and decor, usable water volume is about 53.1 L (14 US gal); filled, the water alone weighs about 166.6 lb (75.5 kg). Figures use the exact 1 US gal = 3.785411784 L conversion and published standard external dimensions, compiled 2026-09-25.
- Nominal size
- 20 US gal
- Standard footprint
- 24×12×16 in
- Nominal volume
- 75.7 L
- Usable volume (90% fill)
- 53.1 L / 14 gal
- Full tank water weight
- 166.6 lb / 75.5 kg
| Fill level | Usable volume (L) | Usable volume (US gal) |
|---|---|---|
| 80% | 45.6 | 12 |
| 90% | 53.1 | 14 |
| 100% | 60.7 | 16 |
Open this size in the calculator
Dimensions, weight, and fill assumptions
These are typical external footprint dimensions published across major US tank manufacturers' standard-size charts, not a measurement of one specific tank on a shelf; rimless, low-iron, and non-US models can differ by an inch or more per side. The nominal 20 US gal rating is the manufacturer's full-tank figure, so it slightly overstates the water you will actually keep: after subtracting a typical 15 L (about 4 US gal) of substrate, decor, and hardscape, and filling to a realistic 90% of the rim height to leave room for equipment and evaporation, usable volume drops to 53.1 L. Water weight uses fresh water at about 25 degrees C (0.997 kg/L, 8.328 lb/US gal); a filled tank also carries the glass, stand, substrate, and hardscape, so total load on a floor or stand is higher than the water weight alone. The prefilled link below opens TankStockPlan with this size's typical external dimensions, a 90% fill, and 15 L of displacement already entered; replace the length, width, and height with your own internal (inside-the-glass) measurements for an exact usable-volume figure, since that is what actually determines how much water and livestock the tank can support. Prioritize animal welfare. A specialist-reviewed husbandry plan and a properly cycled, stable aquarium are required; this calculator is not approval to add fish.