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Fish tank size chart

Dimensions, real water volume and set-up weight for the standard US glass aquarium sizes. Every figure is calculated from the dimensions with the same formulas as our calculators.

Tank	Inches	Centimeters	Rated	Real water	Empty	Set up	Heater
5 gallon	16 × 8 × 10	41 × 20 × 25	5.5 gal	4.7 gal	10 lb	55 lb	25 W
10 gallon	20 × 10 × 12	51 × 25 × 30	10.4 gal	9.1 gal	10 lb	100 lb	50 W
15 gallon	24 × 12 × 12	61 × 30 × 30	15.0 gal	12.9 gal	20 lb	150 lb	50 W
20 gallon high	24 × 12 × 16	61 × 30 × 41	19.9 gal	17.6 gal	25 lb	195 lb	75 W
20 gallon long	30 × 12 × 12	76 × 30 × 30	18.7 gal	16.1 gal	25 lb	185 lb	50 W
29 gallon	30 × 12 × 18	76 × 30 × 46	28.1 gal	25.1 gal	35 lb	270 lb	100 W
40 gallon breeder	36 × 18 × 16	91 × 46 × 41	44.9 gal	39.7 gal	60 lb	435 lb	150 W
40 gallon long	48 × 12 × 16	122 × 30 × 41	39.9 gal	34.9 gal	60 lb	390 lb	150 W
55 gallon	48 × 13 × 21	122 × 33 × 53	56.7 gal	50.8 gal	80 lb	545 lb	2 × 100 W
65 gallon	36 × 18 × 24	91 × 46 × 61	67.3 gal	59.6 gal	120 lb	660 lb	2 × 100 W
75 gallon	48 × 18 × 21	122 × 46 × 53	78.5 gal	69.2 gal	135 lb	770 lb	2 × 150 W
90 gallon	48 × 18 × 24	122 × 46 × 61	89.8 gal	79.8 gal	150 lb	870 lb	2 × 150 W
125 gallon	72 × 18 × 21	183 × 46 × 53	117.8 gal	104.4 gal	190 lb	1,145 lb	2 × 200 W
150 gallon	72 × 18 × 28	183 × 46 × 71	157.1 gal	138.5 gal	315 lb	1,555 lb	2 × 250 W

Real water: inside the glass, filled 1 inch below the rim, no substrate. Set up: plus 2 inches of wet gravel. Heater: to hold 78 °F in a 68 °F room. Have an unusual tank? Use the volume calculator or the weight calculator.

Choosing a size

Bigger is easier. More water dilutes mistakes and holds temperature better. A 20 long or 29 is a forgiving first tank; 5–10 gallons suit a betta or shrimp.
Footprint matters more than gallons. Bottom dwellers and active swimmers use floor area and length. A 20 long beats a 20 high; a 40 breeder beats a 40 long for aquascaping.
Check the floor and the stand. Above about 55 gallons, set-up weight passes 500 lb.