Skip to content

FishTankSizes.comThe aquarist’s blueprint and field guide

Every standard fish tank size, measured

Dimensions, weight, gear and what fits, for 20 aquariums from 2.5 to 180 gallons. Plus free calculators and sourced guides.

Better tanks,
happier fish

Watercolor of a planted aquarium with driftwood, rocks and a school of tetras

Know the size→Plan with confidence→Build a better tank

Popular tank sizes

See all 20 sizes

Standard aquarium size chart

Measure your own tank

Outside dimensions in inches, length × width × height. Water is to the brim. Weights in pounds are our estimates; filled includes two inches of gravel.

Tank	L × W × H (in)	Gallons	Litres	Empty (lb)	Filled (lb)	Heater
Small tanks · Up to 20 gallons
2.5 Gallon	12 × 6 × 8	2.5	10	4	33	25 W
5 Gallon	16 × 8 × 10	5.5	19	7	62	25 W
10 Gallon	20 × 10 × 12	10.4	38	10	115	50 W
15 Gallon	24 × 12 × 12	15	57	20	176	75 W
20 Gallon High	24 × 12 × 16	19.9	76	24	222	100 W
20 Gallon Long	30 × 12 × 12	18.7	76	23	229	100 W
Medium tanks · 29 to 75 gallons
29 Gallon	30 × 12 × 18	28.1	110	42	323	150 W
30 Gallon Breeder	36 × 18 × 12	33.7	114	44	364	150 W
33 Gallon Long	48 × 13 × 12	32.4	125	47	390	150 W
37 Gallon	30 × 12 × 24	37.4	140	54	401	150 W
40 Gallon Breeder	36 × 18 × 16	44.9	151	54	457	200 W
55 Gallon	48 × 13 × 21	56.7	208	90	616	250 W
60 Gallon Breeder	48 × 18 × 16	59.8	227	84	678	250 W
65 Gallon	36 × 18 × 24	67.3	246	91	704	300 W
75 Gallon	48 × 18 × 21	78.5	284	123	842	300 W
Large tanks · 90 gallons and up
90 Gallon	48 × 18 × 24	89.8	341	137	980	2 x 200 W
120 Gallon	48 × 24 × 24	119.7	454	156	1,281	2 x 250 W
125 Gallon	72 × 18 × 22	123.4	473	178	1,360	2 x 250 W
150 Gallon	72 × 18 × 28	157.1	568	286	1,677	2 x 300 W
180 Gallon	72 × 24 × 24	179.5	681	286	1,974	2 x 400 W

Brands differ by up to an inch, and weights are estimates worked out from glass thickness. Treat them as close, not exact. How we source our numbers.

Fish guides

All fish guides

BettaTank size, heater and tank mates.Read guide

Neon tetraThe smallest tank for a proper school.Read guide

GoldfishHow many gallons each goldfish needs.Read guide

AngelfishWhy height and width both matter.Read guide

Guides

Best first tank sizeBigger than you think. Most sources point beginners to 20 to 40 gallons, because more water is more forgiving.Read guide

Cycling a new tankA new tank has no bacteria to process fish waste. Cycling grows them first, and it usually takes four to eight weeks.Read guide

Water changesAbout a quarter of the water each week suits most tanks. Your nitrate reading tells you whether yours needs more.Read guide

Filter flow rate (GPH)Aim for a filter rated at four to six times your tank’s volume per hour, then expect it to move less than the box says once it is full of media.Read guide

Aquarium heater sizeMost sources land between 3 and 5 watts per gallon. The right end of that range depends on how cold your room gets, not just on the tank.Read guide

Choosing substrateGravel is the easy default. Sand suits bottom-sifting fish, soil suits plants, and crushed coral or aragonite is for hard-water fish.Read guide

Stands and floor weightA filled tank weighs about 10 pounds per gallon and puts all of it on a small patch of floor. Here is how to place one safely.Read guide

Glass vs acrylicGlass is cheaper and resists scratches. Acrylic is lighter, tougher and clearer at thickness, but scratches easily and needs full support underneath.Read guide

All tanks at the same scale

Back to the chart

Each tank drawn from the front on a 30 inch stand, next to a 5 ft 8 in person. Pick any tank for its full measurements.

Free calculators

About the calculators

Stocking calculatorCheck how many fish fit, and whether they get along.Volume calculatorGallons and liters for six tank shapes, at your real water line.Weight calculatorWhat a filled tank weighs, and the load it puts on your floor.Substrate calculatorPounds and bags of gravel, sand or soil for any depth.

How many fish, and which tank

How many fish in a 5 gallon tankA betta, or a few tiny fish.How many fish in a 10 gallon tankAbout 8 to 10 small fish.How many fish in a 20 gallon tankAround 15 small fish, in the right mix.How many fish in a 29 gallon tankA school of 12, plus a few bottom fish.How many fish in a 40 gallon tankRoom for a pair of dwarf cichlids with a school.How many fish in a 55 gallon tankBig schools, or a first cichlid tank.How many fish in a 75 gallon tankAngelfish, discus or a rainbowfish community.20 gallon long vs 20 gallon highSame water, different floor space.29 gallon vs 40 gallon breederThe two most common step-up tanks.