Common Aquarium Dimensions Chart
Standard aquarium dimensions for 5 to 125 gallon tanks in inches and centimeters. Length, width, and height for every common size to plan stands, lids, lights, and footprints.
Before you buy a tank, a lid, a light, or a stand, you need its exact footprint and height. Two tanks of the same volume can have very different shapes, which changes how your fish swim, how the tank fits your space, and which accessories will fit. This chart lists the standard dimensions for the most common aquarium sizes in both inches and centimeters.
Quick answer: A 10 gallon tank is about 20 x 10 x 12 inches (51 x 25 x 30 cm), a 40 breeder is 36 x 18 x 17 inches (91 x 46 x 43 cm), a 55 gallon is 48 x 13 x 21 inches (122 x 33 x 53 cm), and a 125 gallon is 72 x 18 x 23 inches (183 x 46 x 58 cm). Dimensions are length x width x height. Confirm your real volume with our aquarium volume calculator and plan the loaded weight on your stand with the aquarium weight calculator.
Standard aquarium dimensions chart
Dimensions are nominal length x width x height for standard rectangular glass tanks, listed in inches and rounded centimeters (1 inch = 2.54 cm). Actual sizes vary slightly by manufacturer because of glass thickness and trim.
| Tank size | L x W x H (inches) | L x W x H (cm) | Footprint (L x W) |
|---|---|---|---|
| 5 gallon | 16 x 8 x 10 in | 41 x 20 x 25 cm | 16 x 8 in |
| 10 gallon | 20 x 10 x 12 in | 51 x 25 x 30 cm | 20 x 10 in |
| 20 gallon high | 24 x 12 x 17 in | 61 x 30 x 43 cm | 24 x 12 in |
| 20 gallon long | 30 x 12 x 13 in | 76 x 30 x 33 cm | 30 x 12 in |
| 29 gallon | 30 x 12 x 19 in | 76 x 30 x 48 cm | 30 x 12 in |
| 40 gallon breeder | 36 x 18 x 17 in | 91 x 46 x 43 cm | 36 x 18 in |
| 55 gallon | 48 x 13 x 21 in | 122 x 33 x 53 cm | 48 x 13 in |
| 75 gallon | 48 x 18 x 21 in | 122 x 46 x 53 cm | 48 x 18 in |
| 90 gallon | 48 x 18 x 25 in | 122 x 46 x 64 cm | 48 x 18 in |
| 125 gallon | 72 x 18 x 23 in | 183 x 46 x 58 cm | 72 x 18 in |
How to read the chart
The first number, length, tells you how wide a space and stand you need. The second, width or depth, is the front-to-back measurement that decides how much room fish have to turn and how easy the tank is to aquascape. The third, height, affects lighting and maintenance: anything past about 24 inches makes planting, cleaning, and getting light to the substrate harder.
Pay special attention to the footprint, length times width, because that is what determines surface area for gas exchange and usable floor space for your fish. It is also the area your stand and floor must support. A 40 breeder and a 55 hold similar volumes but the breeder is far wider front to back, which most fish and aquascapers prefer.
Matching tanks to stands, lids, and lights
Lids, glass tops, and most lights are sold to fit standard footprints, so a 48 inch fixture suits a 55, 75, or 90 gallon tank, while a 24 inch fixture fits a 20 high. Because exact outside dimensions drift between brands, always measure your specific tank before ordering an accessory that has to sit on the rim or clip to the glass. A light an inch too long will not seat properly on the frame.
Stand width should match or slightly exceed the tank length, and the stand must support the full loaded weight, not just the empty glass. A filled tank weighs roughly 10 pounds per gallon once water, substrate, and decor are in, so a 125 gallon can top 1,400 pounds. Run your size through the weight calculator before choosing a stand or placing the tank on an upper floor.
Same volume, different shape
The 20 high versus 20 long pair is the clearest example of why shape matters. Both hold 20 gallons, but the long version trades height for an extra six inches of length, giving more swimming room and surface area. For most community fish, longer and wider beats taller. The 40 breeder takes this further, offering one of the best footprints in the hobby in a tank that still fits a 36 inch stand.
When you are choosing between sizes, think about the fish first. Active swimmers and schooling species want length, bottom dwellers want floor space, and tall plants want height. Use our minimum tank size calculator to find the smallest sensible footprint for a given species, then the stocking calculator to plan a balanced community around your chosen tank.
Confirm your real numbers
Published dimensions are nominal and rounded, so measure the inside of your tank before you trust a volume. Glass thickness, trim, and the exact mold all shift the figures slightly. Enter your real inside length, width, and water height into the volume calculator for an accurate gallon count, which you will need for dosing, stocking, and equipment sizing. For volume unit conversions, see our gallons to liters chart, and browse every quick-lookup table in the reference charts hub.
Frequently Asked Questions
What are the dimensions of a standard 55 gallon tank?
A standard 55 gallon aquarium is about 48 inches long, 13 inches wide, and 21 inches tall, or roughly 122 x 33 x 53 centimeters. That long, narrow footprint is why a 55 is popular for stand-mounted community tanks but is considered shallow front to back, which can make aquascaping and housing larger fish a little tight compared to a 75 with the same length but more width.
What is the difference between a 20 high and a 20 long?
Both hold 20 gallons but the shape differs. A 20 high is about 24 x 12 x 17 inches, taller and more compact. A 20 long is about 30 x 12 x 13 inches, lower and stretched out. The 20 long gives more surface area for gas exchange and more floor space for bottom dwellers and schooling fish, so most aquarists prefer it for community setups, while the 20 high suits tall plants or a narrow spot.
Are aquarium dimensions exact between brands?
No. These are nominal sizes for standard rectangular glass tanks, which is what brands like Aqueon and Tetra build. Real outside dimensions vary by a fraction of an inch between manufacturers because of glass thickness and trim, and inside dimensions vary a bit more. Always measure your specific tank before buying a lid, light, or stand, and confirm volume with our volume calculator rather than the label.
Why does footprint matter more than height?
Footprint, the length times the width, decides how much swimming and floor space your fish actually get, and how much surface area is available for oxygen exchange. Two tanks of equal volume can have very different footprints, like the 40 breeder versus a 55. Wider, longer tanks suit most fish better than tall ones, and they are easier to aquascape and clean because light reaches the substrate.
What is a 40 breeder good for?
The 40 breeder is a favorite because of its wide 36 x 18 inch footprint and modest 17 inch height. That shape gives lots of floor space and surface area in a tank that still fits a 36 inch stand, making it excellent for cichlids, bottom dwellers, planted scapes, and even some reef nano builds. It holds the same 40 gallons as taller designs but is far more usable for most livestock.
How do I convert tank dimensions to centimeters?
Multiply inches by 2.54 to get centimeters. So a 24 inch length is about 61 cm, and an 18 inch width is about 46 cm. The chart below lists both units so you can match lids, lights, and backgrounds sold in either system. For volume conversions between gallons and liters, see our gallons to liters chart and the aquarium unit converter.
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