Aquarium size chart
Standard fish tank sizes and aquarium tank dimensions from 5 to 125 gallons, in inches, centimetres and litres.
| Tank | Inches (L x W x H) | Centimetres | Litres | Water weight (lb) |
|---|---|---|---|---|
| 5 gallon | 16 x 8 x 10 | 40.6 x 20.3 x 25.4 | 19 | 42 |
| 10 gallon | 20 x 10 x 12 | 50.8 x 25.4 x 30.5 | 38 | 83 |
| 20 gallon | 24 x 12 x 16 | 61 x 30.5 x 40.6 | 76 | 167 |
| 20 gallon long | 30 x 12 x 12 | 76.2 x 30.5 x 30.5 | 76 | 167 |
| 29 gallon | 30 x 12 x 18 | 76.2 x 30.5 x 45.7 | 110 | 242 |
| 30 gallon | 36 x 12 x 16 | 91.4 x 30.5 x 40.6 | 114 | 250 |
| 40 gallon breeder | 36 x 18 x 16 | 91.4 x 45.7 x 40.6 | 151 | 334 |
| 50 gallon | 36 x 18 x 19 | 91.4 x 45.7 x 48.3 | 189 | 417 |
| 55 gallon | 48 x 13 x 21 | 121.9 x 33 x 53.3 | 208 | 459 |
| 60 gallon | 48 x 13 x 22 | 121.9 x 33 x 55.9 | 227 | 500 |
| 75 gallon | 48 x 18 x 21 | 121.9 x 45.7 x 53.3 | 284 | 626 |
| 90 gallon | 48 x 18 x 24 | 121.9 x 45.7 x 61 | 341 | 751 |
| 100 gallon | 72 x 18 x 18 | 182.9 x 45.7 x 45.7 | 379 | 834 |
| 125 gallon | 72 x 18 x 21 | 182.9 x 45.7 x 53.3 | 473 | 1,042 |
Standard fish tank sizes explained
Aquariums in the US are sold by nominal gallon size, and most manufacturers build to the same standard dimensions, so fish tank specs such as length and footprint are similar between brands. Small differences of a fraction of an inch are common, so check the label before ordering a custom lid or stand.
Tanks that share a footprint
Several sizes use the same floor area, which makes upgrading easier because the same stand often fits:
- 20 gallon long and 29 gallon: 30 x 12 inches
- 40 gallon breeder and 50 gallon: 36 x 18 inches
- 75 gallon and 90 gallon: 48 x 18 inches
Check your stand's rated weight before moving to a taller tank on the same footprint. The 20 long vs 29 gallon comparison walks through one of the most common upgrades.
How heavy are these tanks?
Water alone weighs about 8.34 lb per gallon, so even mid-size tanks need a proper stand. The fish tank weight guide lists the full weight of every size.
Measure your own tank
If your tank isn't a standard size, use the aquarium volume calculator with your own measurements. Then work out how much gravel or sand it needs.
Frequently asked questions
What are standard aquarium sizes?
Common US sizes include 5, 10, 20, 29, 40 breeder, 55, 75 and 125 gallons. Many share footprints: the 20 long and 29 gallon are both 30 x 12 inches, and the 75 and 90 gallon are both 48 x 18 inches.
Why do tanks of the same size have different dimensions?
Each manufacturer builds to slightly different specs, and some sizes come in long, tall or breeder shapes. Always check the measurements on your tank's label or the maker's website.
Are these inside or outside measurements?
They are typical outside measurements, the size you need for a stand or a space in your home. Inside measurements are smaller by the glass thickness.