Aquarium Calculator

Select Tank Shape:

Length :

in ▾

Width :

m ▾

Height :

m ▾

Front Pane :

ft ▾

End Pane :

ft ▾

Radius:

ft ▾

Radius 2:

ft ▾

Radius 1:

ft ▾

Length Short side:

ft ▾

Length Long side:

ft ▾

Width 1:

ft ▾

Width 2:

ft ▾

Length 1:

ft ▾

Length 2:

ft ▾

Fill Depth (Optional):

ft ▾

Full Width :

ft ▾

Use this aquarium calculator to measure the volume of your fish tank and determine the exact amount of water needed to fill it. Accurate water volume is essential for proper aquarium care, including the right number of fish, correct medication doses, and effective tank maintenance. It also helps in selecting the correct aquarium size, powerheads, or return pumps.

How to Estimate Aquarium Water Volume?

Since aquariums come in different shapes and dimensions, each requires a specific calculation formula to determine water volume accurately. Below are the formulas for the most common aquarium shapes:

Rectangular Prism Shape:

rectangular fish tank

Volume = Height × Width × Length

Cubic Shape:

cubic fish tank

Volume = Length³

Regular Hexagonal Shape:

All sides are equal. Volume = ((3√3)/2) × (Front Width)² × Height

Flat Back Hexagon Shape:

flat back hexagonal fish tank

Volume = ((((3√3)/2) × (Front Width)²)/2 + (Side × Length)) × Height

Octagonal Shape:

octagonal fish tank

Volume = 2 × (Front Width)² × (1 + √2) × Height

Cylindrical Shape:

cylindrical fish tank

Regular Cylinder:

Volume = π × (Diameter / 2)² × Height

Half Cylinder:

half cylindrical fish tank

Volume = (π × (Diameter / 2)² × Height) / 2

Quarter Cylinder:

quarter cylindrical fish tank

Volume = π × Radius² × Height / 4

Note: Diameter = 2 × Radius

Bow Front Shape:

bow front fish tank

Volume = Height × Width × Length + 0.5 × r² × (α − sin(α)) × Height

α = Central angle of the curved section
r = Radius of the bow front curve

L Shaped Tank:

L shaped fish tank

Volume = ((Length1 × Width1) + ((Length2 − Width1) × Width2)) × Height

Elliptical Shape:

elliptical fish tank

Volume = π × Radius1 × Radius2 × Height

Corner Prism Tank:

corner prism fish tank

Volume = ((Length1 × Length2)/2) × Height

Use these formulas to calculate your aquarium volume and verify your results with our online Aquarium Calculator.

Aquarium Weights & Sizes

SMALL-SIZED AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
2 1/2 gallon	12″ x 6″ x 8″	3	3	26.9	27.4
5 gallon	16″ x 8″ x 10″	7	10	58.7	59.8
10 gallon “Leader”	20″ x 10″ x 12″	11	15	109.5	111.5
15 gallon	24″ x 12″ x 12″	21	25	171.2	174.3
15 gallon High	20″ x 10″ x 18″	22	25	172.2	175.3

MID-SIZED AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
20 gallon High	24″ x 12″ x 16″	25	30	221.9	226.1
20 gallon Long	30″ x 12″ x 12″	25	30	221.9	226.1
25 gallon	24″ x 12″ x 20″	32	40	280.6	285.9
29 gallon	30″ x 12″ x 18″	40	45	327	333.1
30 gallon Breeder	36″ x 18″ x 12″	48	48	346.4	352.6
40 gallon Breeder	36″ x 18″ x 16″	58	60	451.8	460.2
40 gallon Long	48″ x 12″ x 16″	55	60	448.8	457.2

LARGE AQUARIUMS
Tank Size	L x W x H	Empty Weight	Plants & Rocks	Filled Weight Freshwater (Including Plants & Rocks)	Filled Weight Saltwater (Including Plants & Rocks)
	Inches	lbs	lbs	lbs	lbs
50 gallon	36″ x 18″ x 19″	100	70	587.3	597.7
55 gallon	48″ x 13″ x 21″	107	75	641	652.5
65 gallon	36″ x 18″ x 24″	126	90	758.5	772
75 gallon	48″ x 18″ x 21″	140	110	875.9	891.6
90 gallon	48″ x 18″ x 24″	160	120	1031.1	1049.9
125 gallon	72″ x 18″ x 21″	206	130	1379.2	1405.3
150 gallon	72″ x 18″ x 28″	338	140	1729.8	1761.1
180 Gallon	72″ x 24″ x 25″	350	170	2022.2	2059.7
225 Gallon	72″ x 27.5″ x 27.5″	360	190	2427.7	2474.7

Source: saltwateraquarium.com

FAQ’s

Does the Shape of the Aquarium Impact Its Volume?

Yes, each aquarium shape requires a different volume formula. For instance, a rectangular tank uses length × width × height, whereas a cube relies on length³.

What Happens If the Fish Tank Is Too Small?

A small tank can lead to rapid water parameter changes, causing stress and health problems for fish due to the limited water volume.

Are Bigger Aquariums Easier to Maintain?

Yes. Larger tanks offer more stable ecosystems and water parameters, making maintenance easier and providing a healthier environment for fish.