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Aquarium gallons to litres
Convert any common fish tank size between US gallons, UK gallons and litres at a glance. Every figure uses the exact conversion: 1 US gallon = 3.785411784 litres.
US gallons to litres
Nominal tank sizes as sold in the US. A 20-gallon tank holds about 75.7 litres and a 55-gallon about 208 litres. Real tanks often hold slightly more or less than their label, so check your exact size in the volume calculator.
| US gallons | Litres | UK gal |
|---|---|---|
| 5 US gal | 18.9 | 4.2 |
| 10 US gal | 37.9 | 8.3 |
| 15 US gal | 56.8 | 12.5 |
| 20 US gal | 75.7 | 16.7 |
| 29 US gal | 109.8 | 24.1 |
| 30 US gal | 113.6 | 25.0 |
| 40 US gal | 151.4 | 33.3 |
| 55 US gal | 208.2 | 45.8 |
| 65 US gal | 246.1 | 54.1 |
| 75 US gal | 283.9 | 62.5 |
| 90 US gal | 340.7 | 74.9 |
| 125 US gal | 473.2 | 104.1 |
| 150 US gal | 567.8 | 124.9 |
Litres to gallons
Common metric tank sizes sold in Europe, Latin America and Asia, in US and UK gallons. A 100-litre tank is about 26.4 US gallons or 22 UK gallons.
| Litres | US gal | UK gal |
|---|---|---|
| 20 L | 5.3 | 4.4 |
| 30 L | 7.9 | 6.6 |
| 40 L | 10.6 | 8.8 |
| 54 L | 14.3 | 11.9 |
| 60 L | 15.9 | 13.2 |
| 80 L | 21.1 | 17.6 |
| 100 L | 26.4 | 22.0 |
| 120 L | 31.7 | 26.4 |
| 150 L | 39.6 | 33.0 |
| 200 L | 52.8 | 44.0 |
| 240 L | 63.4 | 52.8 |
| 300 L | 79.3 | 66.0 |
| 400 L | 105.7 | 88.0 |
| 500 L | 132.1 | 110.0 |
US gallons vs UK gallons
They are different units. A US gallon is 3.785 litres, while a UK (imperial) gallon is 4.546 litres, about 20% larger. So a tank sold as 20 gallons in the US holds about 16.7 UK gallons. Tanks and products from the UK quote imperial gallons; most aquarium products sold worldwide use US gallons.
How to convert
Multiply US gallons by 3.785 to get litres, or divide litres by 3.785 to get US gallons. For UK gallons, use 4.546 instead. From tank dimensions, length × width × height in centimetres ÷ 1,000 gives litres, and in inches ÷ 231 gives US gallons.
Frequently asked questions
- How many litres is a 20 gallon fish tank?
- A 20 US gallon tank holds about 75.7 litres (20 × 3.785). A '20 long' (30 × 12 × 12 in) measures 70.8 litres from its outside dimensions, and a '20 high' (24 × 12 × 16 in) about 75.5 litres.
- How many litres is a 29 gallon tank?
- About 109.8 litres (29 × 3.785). The standard 29-gallon tank (30 × 12 × 18 in) measures 106.2 litres from its outside dimensions.
- How many litres is a 55 gallon tank?
- About 208 litres (55 × 3.785). The common 48 × 13 × 21 inch 55-gallon tank measures 214.7 litres from its outside dimensions and holds a little less water once you allow for the glass and substrate.
- How many gallons is a 100 litre aquarium?
- About 26.4 US gallons, or 22 UK gallons.
- How many gallons is a 200 litre tank?
- About 52.8 US gallons, or 44 UK gallons.