Standard Aquarium Sizes Chart — Dimensions, Gallons & Weight
Complete reference of every standard aquarium size from 1 gallon to 220+ gallons — external and internal dimensions, nominal vs. actual gallons, glass thickness by tank height, filled water weight, and the best variant for each fish species and setup style. Whether you are browsing to buy, checking a sticker against reality, or comparing a Long vs. a High tank, this is the page to keep open.
Why You Need a Standard Aquarium Sizes Chart (Instead of Guessing)
The aquarium industry is loose with numbers. A 55 gallon tank advertises 55 gallons — but its outside dimensions compute to about 58 gallons, and subtracting glass wall thickness leaves roughly 52 gallons of actual water. A "220 gallon" Corner tank is labeled from a full rectangular box it never actually holds. Even the same nominal size from two brands can differ by several gallons because one rounds the nameplate up and the other rounds it down, uses thicker or thinner glass, or adds internal bracing that eats into the footprint.
That is a problem, because every downstream decision depends on the real number: how much water conditioner, how many fish, whether your stand is rated for the filled weight, how much light you need over the water surface, and whether a filter rated for "60 gallons" will actually cycle a 52 gallon tank. Guess on any of those and the tank suffers — fish get stressed, filters underperform, stands sag, or the setup simply looks wrong because the light is too strong or too weak for the actual water volume.
This guide is the correction. It lists every standard size from 1 gallon columns to 220+ gallon custom corners with both the advertised gallons and the geometric gallons you get from the box dimensions. It explains why each variant exists — Long vs. High vs. Breeder vs. Column — and gives you the glass thickness that the height demands. Use it first when you are buying, then open the fish tank volume calculator to verify the exact tank you already own by entering its inside dimensions and subtracting its glass.
Complete Standard Aquarium Sizes Chart
Advertised and geometric gallons, external dimensions in inches and centimeters, glass thickness by height, filled water weight (at 8.34 lbs per gallon), and the best use case. All dimensions are outside measurements as printed on the box. Water weight excludes the tank glass, stand, substrate, and decorations — use it as the water-only baseline for floor loading.
| Model | Variant | Dims (L×W×H) | Nominal Gal | Actual Gal | Glass Thickness | Water Weight | Best For |
|---|---|---|---|---|---|---|---|
| 1 gal Column | Column | 8 x 8 x 12 in 20 x 20 x 30 cm | 1 | 3.3(+nom) | 4 - 4.5 mm (3/16 in) | 27.5 lb | Betta cube, nano shrimp |
| 2.5 gal Column | Column | 10 x 10 x 12 in 25 x 25 x 30 cm | 2.5 | 5.2(+nom) | 4 - 4.5 mm (3/16 in) | 43.4 lb | Dwarf puffer, planted nano |
| 5 gal Column | Column | 14 x 14 x 12 in 36 x 36 x 30 cm | 5 | 10.2(+nom) | 4 - 4.5 mm (3/16 in) | 85.1 lb | Small community, betta sorority |
| 10 gal Standard | Standard | 20 x 10 x 12 in 51 x 25 x 30 cm | 10 | 10.4 | 4 - 4.5 mm (3/16 in) | 86.7 lb | Starter community, shrimp |
| 15 gal High | High | 20 x 13 x 16 in 51 x 33 x 41 cm | 15 | 18(+nom) | 6 mm (1/4 in) | 150.1 lb | Small planted tank |
| 15 gal Long | Long | 24 x 13 x 12 in 61 x 33 x 30 cm | 15 | 16.2(+nom) | 4 - 4.5 mm (3/16 in) | 135.1 lb | Top-dwelling species |
| 20 gal Standard | Standard | 24 x 12 x 16 in 61 x 30 x 41 cm | 20 | 19.9 | 6 mm (1/4 in) | 166 lb | Most popular beginner tank |
| 20 gal Long | Long | 30 x 12 x 12 in 76 x 30 x 30 cm | 20 | 18.7(-corner) | 4 - 4.5 mm (3/16 in) | 156 lb | African cichlids, long profile |
| 29 gal Breeder | Breeder | 30 x 18 x 12 in 76 x 46 x 30 cm | 29 | 28.1 | 4 - 4.5 mm (3/16 in) | 234.4 lb | N. American cichlids, breeding |
| 30 gal Column | Column | 16 x 16 x 36 in 41 x 41 x 91 cm | 30 | 39.9(+nom) | 12 mm+ (1/2 in), bracing required | 332.8 lb | Vertical aquascaping, discus |
| 40 gal Standard | Standard | 36 x 13 x 20 in 91 x 33 x 51 cm | 40 | 40.5 | 8 mm (5/16 in) | 337.8 lb | Community, mid-size reef |
| 40 gal Breeder | Breeder | 36 x 18 x 16 in 91 x 46 x 41 cm | 40 | 44.9(+nom) | 6 mm (1/4 in) | 374.5 lb | Native fish, large planted |
| 50 gal Long | Long | 36 x 18 x 18 in 91 x 46 x 46 cm | 50 | 50.5 | 6 mm (1/4 in) | 421.2 lb | South American cichlids |
| 50 gal Column | Column | 18 x 18 x 36 in 46 x 46 x 91 cm | 50 | 50.5 | 12 mm+ (1/2 in), bracing required | 421.2 lb | Marine column, deep reef |
| 55 gal Standard | Standard | 48 x 13 x 21 in 122 x 33 x 53 cm | 55 | 56.7(+nom) | 8 mm (5/16 in) | 472.9 lb | Reef tank baseline |
| 60 gal Column | Column | 20 x 20 x 36 in 51 x 51 x 91 cm | 60 | 62.3(+nom) | 12 mm+ (1/2 in), bracing required | 519.6 lb | Tall planted tank, arowana |
| 75 gal Standard | Standard | 48 x 18 x 20 in 122 x 46 x 51 cm | 75 | 74.8 | 8 mm (5/16 in) | 623.8 lb | Most popular community tank |
| 90 gal Long | Long | 48 x 18 x 24 in 122 x 46 x 61 cm | 90 | 89.8 | 8 mm (5/16 in) | 748.9 lb | Deep-water look, large fish |
| 90 gal High | High | 48 x 19 x 24 in 122 x 48 x 61 cm | 90 | 94.8(+nom) | 8 mm (5/16 in) | 790.6 lb | Aquascaping competition tank |
| 100 gal Column | Column | 24 x 24 x 36 in 61 x 61 x 91 cm | 100 | 89.8(-corner) | 12 mm+ (1/2 in), bracing required | 748.9 lb | Marine centerpiece tank |
| 125 gal Standard | Standard | 72 x 18 x 20 in 183 x 46 x 51 cm | 125 | 112.2(-corner) | 8 mm (5/16 in) | 935.7 lb | Large marine, monster fish |
| 150 gal Long | Long | 72 x 18 x 28 in 183 x 46 x 71 cm | 150 | 157.1(+nom) | 10 mm (3/8 in) | 1310.2 lb | Deep reef, large angels |
| 150 gal Column | Column | 30 x 30 x 36 in 76 x 76 x 91 cm | 150 | 140.3(-corner) | 12 mm+ (1/2 in), bracing required | 1170.1 lb | Premium marine, custom stand |
| 180 gal Standard | Standard | 72 x 24 x 25 in 183 x 61 x 64 cm | 180 | 187(+nom) | 10 mm (3/8 in) | 1559.6 lb | Show tank, large community |
| 220+ gal Custom Corner | Corner | 48 x 48 x 30 (advertised) in 122 x 122 x 76 cm | 220 | 234.9(+nom) | 10 mm (3/8 in) | 1958.8 lb | Custom marine, floor-to-ceiling |
Actual gallons = box dimensions × 0.785 for Corner tanks (π/4 correction for the cutaway wedge). Nominal gallons are the industry-advertised label. Water weight = actual gallons × 8.34 lbs.
Quick Lookup — Dimensions to Gallons
You know your tank is 48 × 18 × 20. How many gallons is that? Paste any outside dimensions here and we compute the exact geometric gallons, convert to liters, give you the filled water weight, and point you to the closest standard tank in the chart above. For non-rectangular shapes or glass-wall corrections, open the calculator.
Lookup Gallons From Any Dimensions
Type any length × width × height in inches. We give you the exact geometric gallons, liters, filled weight, and the closest standard tank on the chart above. This is a quick reference — if you need to subtract glass wall thickness or try non-rectangular shapes, open the full fish tank volume calculator.
Geometric Result
74.8
US Gallons
283
Liters
624
lbs H2O
Closest Standard Tank
75 gal Standard (75 gal)
Advertised dims: 48 x 18 x 20 in · Standard · Most popular community tank
Note: nominal vs. geometric differ by how the brand rounds. Compare against the table above before purchasing.
First Principles — Why the Variants Exist
💡 Why Long and High are Not Interchangeable
Two tanks can share the same advertised gallons while serving opposite purposes. Volume is length × width × height. A 20 gal Long (30 × 12 × 12) spreads its water across a shallow footprint, which means low water pressure on the glass, a wide swimming lane for top-dwelling and schooling fish, and a more forgiving light spread that works well for planted tanks with low-to-mid light requirements. A 20 gal High (24 × 12 × 16) packs the same volume into a taller column — it creates more vertical swim space for discus or angelfish, a larger viewing window, and more water pressure on the front glass (hence the thicker glass recommendation for anything over 16 inches tall).
Rule of thumb: pick Long when your fish swim horizontally (cichlids, tetras, danios) or you want a planted tank. Pick High when they swim vertically (discus, angels) or when your room has limited wall width but ceiling height to spare.
⚠️ Corner Tanks Are 21.5% Less Than Advertised
A corner aquarium sits flush against two perpendicular walls, so it uses only the quadrant of its bounding rectangular box. The volume is π/4 ≈ 0.785 of the full box — always. A "220 gallon" corner tank (48 × 48 × 30 inches advertised) actually holds about 173 gallons. Brand websites never do this math for you because the higher number sells better, but every purchase decision downstream depends on the real number: filter sizing, floor loading, fish count, and UV sterilizer capacity. Multiply the advertised gallons by 0.785 for a corner tank, or use the calculator's corner/oval shape and input the bounding box.
❌ Don't Use a Breeder Tank as a Showcase Tank
Breeder tanks (29 gal = 30 × 18 × 12, 40 gal = 36 × 18 × 16) are intentionally short. That low water column serves a purpose — it reduces water pressure for the fish, makes fry access to the surface easier, and lets breeders net babies quickly from the front without disturbing a deep water column. But that same short height makes a terrible showcase tank: the viewing window feels cramped, fish have no vertical swim space, and planted tanks struggle because light has too little distance to spread. If you want a showcase, look at the Long or High variant of the same footprint, or step up to the next standard size that gives you 18+ inches of height.
Glass Thickness by Tank Height — The Pressure Rule
Water pressure at the bottom of a tank is purely a function of height: 0.036 psi per inch of water column, or roughly 0.433 psi per foot. A 12 inch tank bottom sees about 0.43 psi; a 30 inch column sees 1.08 psi. The front glass must resist that pressure multiplied by its area, and thinner glass deflects more under load, which can fatigue the silicone seal over time. The industry uses the following thickness bands, and the chart above follows them for every tank by its advertised height.
Tank Height
Up to 10 in
3.5–4 mm (1/8 in)
Betta cubes, 1–5 gal columns
Tank Height
12 in
4–4.5 mm (3/16 in)
10 gal standard, 20 gal long
Tank Height
15 in
5 mm (3/16 in)
15 gal high
Tank Height
18 in
6 mm (1/4 in)
40 gal breeder, 50 gal long
Tank Height
24 in
8 mm (5/16 in)
90 gal long, 50 gal column
Tank Height
30 in+
10 mm+ (3/8 in)
100–220 gal, eurobrace required
How Much Weight Does Your Floor Actually See?
Water is the single heaviest component of any aquarium setup. Every US gallon weighs 8.34 lbs, so a tank that holds 75 gallons of water puts 625 lbs of water alone on whatever it sits on. Add glass (roughly 50–80 lbs for a 75 gal), a stand (another 60–120 lbs), substrate (gravel = ~10 lbs per gal, sand = ~12 lbs per gal, so 700–900 lbs for 75 gal), live rock in a marine tank (5–15 lbs per gal for the rock itself, plus water it displaces), equipment, and livestock — and a fully set up 75 gal reef can sit at 1,200–1,800 lbs.
Compare that against a typical residential floor rating of 40 lbs per square foot. A 75 gal tank has a footprint of 48 × 18 = 864 sq inches = 6 sq ft. Water alone is 625 lbs ÷ 6 sq ft = 104 lbs/sq ft — already 2.6 times the default floor rating. The stand spreads this load across the entire footprint, but you still need to check that your home's floor joists are properly sized, or place the tank directly over a bearing wall. Large tanks (125 gal and up) almost always require a structural assessment before purchase.
The water weight column in the chart gives you the correct starting point — actual gallons × 8.34 — so you can multiply by your chosen substrate and rock density to arrive at a realistic total before the stand is ordered.
Corner Aquariums — True Capacity & Filter Sizing
The wedge that makes a corner tank a corner tank is exactly π/4 of the full rectangle it sits in. Mathematically, a corner tank is a quarter of a cylinder stretched across the diagonal — but the practical number you need is the ratio: actual gallons ≈ advertised gallons × 0.785. The other 21.5% never exists.
Corner tank math breaks down like this. A brand advertises a 48 × 48 × 30 inch tank as 220 gallons. The full rectangular box would be 48 × 48 × 30 ÷ 231 = 300.8 gallons. The corner quarter is π/4 of that box volume, so 300.8 × 0.785 = 236 gallons of geometric capacity. But brands round that down, often using thicker glass, and the sticker reads "220 gal." Subtract the glass and you land around 195–210 gallons of actual water, not the 220 on the box.
Dims in: 36 × 36 × 28
Dims in: 48 × 48 × 30
Dims in: 54 × 54 × 30
Dims in: 60 × 60 × 36
Filter rule: buy a filter rated for the actual gallons, not the advertised gallons of your corner tank. A rated 220 gal filter on a 173 gal tank will underperform by roughly 25% — enough to cause nitrite spikes in a reef setup.
Frequently Asked Questions
How big is a standard 10 gallon fish tank?▼
A standard 10 gallon aquarium advertises 20 × 10 × 12 inches (51 × 25 × 30 cm) of outside dimension. Geometrically that is about 10.4 gallons (20 × 10 × 12 ÷ 231), so manufacturers round down to a 10 gallon nameplate. After glass wall thickness — typically 4 mm — the inside dimensions are roughly 19.2 × 9.2 × 11.6 inches, yielding about 9.4 gallons of actual water capacity.
What glass thickness does a 55 gallon tank need?▼
A 55 gallon standard tank stands 21 inches tall. The water pressure at the bottom of a 21-inch column is about 0.74 psi, which requires at least 6 mm (1/4 in) glass on the front, back, and sides. Premium brands like Red Sea or Marineland use 8 mm (5/16 in) for extra rigidity. Bracing — either a plastic cross-brace at the top or a eurobrace frame — is standard on any tank over 20 inches tall and is not optional on a 55.
What is the difference between a Long and a High tank of the same gallonage?▼
They hold the same advertised volume but distribute it differently. A 15 gallon Long (24 × 13 × 12) spreads its 15 gallons across a longer footprint and a lower water column; a 15 gallon High (20 × 13 × 16) packs the same volume into a taller, narrower box. The long profile favors top-swimming and schooling species, gives more horizontal swim space, and creates a more natural current. The high profile favors vertical aquascaping, discus, and other mid-water species, but creates more water pressure on the glass and a taller viewing window that can look cramped if the room has low ceilings.
How many gallons does a Corner aquarium really hold?▼
Most corner tanks advertise gallons based on the bounding box (for example, a 48 × 48 × 30 corner is labeled as 220 gallons). But a corner tank uses only π/4 ≈ 78.5% of that box volume — the other 21.5% is the wedge cut out to fit into a corner. So a "220 gallon" corner actually holds about 173 gallons of water. Always multiply the advertised gallons by 0.785 for a true corner tank, or use your fish tank volume calculator with the oval/corner shape selected.
What does "Breeder" mean in aquarium sizing?▼
A Breeder tank is intentionally short in height — typically 12–16 inches — but maintains the same length and width footprint as a taller tank of higher nominal gallons. The shallow water column reduces water pressure and makes maintenance easier, but the real reason is that short tanks give breeding pairs and fry a more accessible top surface for oxygen exchange and allow easier fry removal. A 29 gal Breeder (30 × 18 × 12) and a 40 gal Standard (36 × 13 × 20) sit on very different footprints and serve different fish — breeder tanks are not interchangeable with tall showcase tanks.
How much does a full aquarium weigh?▼
Water weighs 8.34 lbs per US gallon. Multiply the actual water gallons by 8.34 to get the water-only weight. Then add the tank itself (10–25 lbs for small glass, up to 100+ lbs for large), the stand (40–150 lbs), substrate (10–50 lbs for a 55 gal), rock and wood (variable), equipment, and livestock. A fully set up 55 gal reef commonly tops 700–900 lbs; a 125 gal can easily exceed 1,500 lbs. Always check your floor's live-load rating before buying — most residential floors are rated at 40 lbs per sq ft, which a 75 gal tank on a 18 × 48 footprint just barely exceeds.
Pair This Chart With the Calculator
This standard aquarium sizes chart pairs with the main fish tank volume calculator at the site homepage — use the calculator when you need to verify your tank's real capacity, and this guide when you are choosing a size before purchasing. Browse the full guides hub for more reference pages.