Aquarium Sizes Chart: Dimensions & Weights
Standard aquarium sizes from 2.5 to 180 gallons with typical dimensions in inches, empty weight, and filled weight so you can plan a stand, floor, and footprint.
Before you buy a tank, you need three numbers: how much space it takes up, how much it weighs empty, and how much it weighs once it is full of water and gravel. That filled weight is the one that surprises people, because a glass aquarium gains roughly 10 pounds for every gallon it holds. The chart below covers every common standard rectangular size so you can match a tank to your stand, your floor, and your room.
Quick answer: A filled aquarium weighs about 10 pounds per gallon (water is 8.34 lb/gal, glass and substrate add the rest). A 10 gallon tank is roughly 20 x 10 x 12 inches and about 111 lb filled. A 55 gallon is 48 x 13 x 21 inches and about 625 lb filled. A 125 gallon is 72 x 18 x 23 inches and around 1,400 lb filled. Always confirm real volume with our aquarium volume calculator and total load with the aquarium weight calculator.
Standard aquarium sizes chart
Dimensions are nominal length x width x height in inches for standard glass tanks. Filled weight includes water, average gravel, and the glass itself, rounded to the common published figures used by major manufacturers.
| Tank size | Dimensions (L x W x H) | Empty weight | Filled weight |
|---|---|---|---|
| 2.5 gallon | 12 x 6 x 8 in | 3 lb | 27 lb |
| 5 gallon | 16 x 8 x 10 in | 7 lb | 62 lb |
| 10 gallon | 20 x 10 x 12 in | 11 lb | 111 lb |
| 20 gallon high | 24 x 12 x 17 in | 25 lb | 225 lb |
| 20 gallon long | 30 x 12 x 13 in | 25 lb | 225 lb |
| 29 gallon | 30 x 12 x 19 in | 40 lb | 330 lb |
| 40 gallon breeder | 36 x 18 x 17 in | 58 lb | 458 lb |
| 55 gallon | 48 x 13 x 21 in | 78 lb | 625 lb |
| 75 gallon | 48 x 18 x 21 in | 140 lb | 850 lb |
| 90 gallon | 48 x 18 x 25 in | 160 lb | 1,050 lb |
| 125 gallon | 72 x 18 x 23 in | 206 lb | 1,400 lb |
| 150 gallon | 72 x 18 x 28 in | 308 lb | 1,800 lb |
| 180 gallon | 72 x 24 x 25 in | 338 lb | 2,100 lb |
How to read the chart
Dimensions tell you whether a tank physically fits your space and stand. Pay close attention to the footprint, the length times the width, because that is what your stand and floor support. Two tanks of the same volume can have very different footprints, as the 20 high and 20 long pair shows. Height beyond about 24 inches makes planting and cleaning harder and reduces light reaching the substrate.
Empty weight matters when you carry the tank into the house and onto the stand. Filled weight matters forever after. Once a tank is running, it is effectively a permanent fixture, so plan placement carefully the first time. The 10 pounds per gallon estimate is intentionally conservative and already includes substrate, so you can trust it for stand and floor planning.
Matching tank size to a stand and floor
Any tank up to a 29 gallon sits comfortably on a sturdy, level piece of furniture rated for the load, though a purpose-built aquarium stand is always safer. From 40 gallons up, use a real aquarium stand because the cabinet distributes the weight evenly across the rim and the floor. Never set a glass tank on a surface that flexes, and never shim only the corners, because uneven support cracks the bottom panel.
For tanks of 75 gallons and larger, the floor becomes part of the equation. Place the tank perpendicular to the floor joists so the load crosses several joists rather than resting between two, and keep it near a load-bearing wall. A filled 125 gallon at roughly 1,400 pounds concentrates more weight than a household refrigerator, so on upper floors or older homes it is worth confirming structure before you fill.
Beginner-Friendly Tank Kits
Tetra Aquarium 20 Gallon Kit with LED and Filter
$119.14 on Amazon
Complete tropical kit, a forgiving beginner size.
Aqueon Aquarium Starter Kit 20-Gallon
$151.99 on Amazon
Smart Clean filtration and LED, freshwater or saltwater.
Why bigger tanks are easier to keep
It feels backward, but a large aquarium is more forgiving than a small one. A bigger water volume dilutes ammonia and nitrate, so a single overfeeding or a missed water change does less harm. Temperature also swings more slowly in a large body of water, which protects fish during a heater hiccup or a hot afternoon. That stability is the main reason we steer beginners toward 20 gallons or more rather than a desktop nano.
Volume also decides how many fish you can keep. Surface area for gas exchange and total water both rise with tank size, so a 55 gallon supports a far richer community than a 10 gallon. Plan stock against real volume with our stocking calculator, and if you are still choosing a fish first, the minimum tank size calculator tells you the smallest sensible home for a given species.
Confirm your real numbers
Published sizes are a starting point, not gospel. Glass thickness, trim, and the exact mold vary between brands, and your fill line and decor change the working volume. Measure the inside of your tank and run the figures through the volume calculator for an accurate gallon count, then use the weight calculator to get a filled total for your stand and floor. Dose medications and conditioner to that real volume, since most tanks hold about 85 to 90 percent of their rated label once filled.
For more planning tables, browse our full aquarium reference charts, and when you are ready to set up, the calculators hub walks you through volume, weight, heater size, filtration, and stocking in order.
Frequently Asked Questions
How much does a filled aquarium weigh?
A safe rule of thumb is about 10 pounds per gallon once a glass tank is filled with water, substrate, rocks, and equipment. Water alone is 8.34 pounds per gallon, and the glass plus gravel add the rest. A 55 gallon tank lands near 625 pounds, and a 125 gallon near 1,400 pounds, which is why large tanks need a dedicated stand and a load-bearing wall or floor joist underneath.
What is the difference between a 20 gallon high and a 20 gallon long?
Both hold 20 gallons, but the footprint differs. A 20 high is 24 inches long and tall (around 16 inches), while a 20 long is 30 inches long and only 12 inches tall. The 20 long gives more surface area for gas exchange and floor space for bottom dwellers and schooling fish, so most aquarists prefer it for community setups. The 20 high suits tall plants or a small centerpiece display.
Are these aquarium dimensions exact?
They are rounded nominal sizes for standard rectangular glass aquariums, which is what most brands like Aqueon and Tetra produce. Actual outside dimensions vary by a fraction of an inch between manufacturers because of glass thickness and trim. Always measure your specific tank and stand before buying a hood, light, or lid, and confirm your exact volume with our volume calculator rather than trusting the label.
How do I know if my floor can hold a large aquarium?
Tanks up to about 55 gallons sit safely on most floors near a wall. Above roughly 75 to 125 gallons, the concentrated load matters: position the tank perpendicular to the floor joists, ideally near a load-bearing wall, and spread the weight with a proper stand. For 150 gallon or larger setups on an upper floor, consult a contractor. Filled weight is the number that counts, not the empty weight.
Why does my tank hold less water than the label says?
The rated gallons describe the tank to the very top rim. In practice you fill to about an inch below the rim, and substrate, rocks, and decor displace several more gallons. Real water volume is usually around 85 to 90 percent of the label. This matters when you dose medication or water conditioner, so calculate doses on actual volume using our volume calculator, not the printed rating.
What size tank is best for a beginner?
A 20 gallon long or a 29 gallon is the easiest starting point. Bigger water volumes dilute waste and resist sudden swings in temperature and pH, so they forgive early mistakes far better than a tiny 2.5 or 5 gallon. Nano tanks look simple but crash fast. If space and budget allow, start at 20 gallons or larger and use our stocking calculator to plan a sensible community.
Planning or running a tank?
Use our free calculators and guides to get every number right.
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