Aquarium Shapes — Find the Right Volume Calculator
Aquariums come in more than 20 distinct shapes, and each one requires a specific formula to calculate water volume accurately. Browse every shape below, learn what makes each one unique, and jump directly to the matching volume calculator.
Standard Aquarium Shapes
Rectangular
The rectangular aquarium is the most common fish tank shape, found in sizes from desktop nano tanks to massive display setups.
Calculate VolumeCube
Cube aquariums are popular in modern aquascaping for their equal dimensions, which create a balanced visual perspective from all angles.
Calculate VolumeBreeder
Breeder aquariums share the rectangular shape but feature a wider front-to-back depth and shorter height than standard tanks.
Calculate VolumeShallow
Shallow aquariums prioritize surface area over depth, making them excellent for planted tanks where light must reach the substrate and for paludariums that combine aquatic and terrestrial elements.
Calculate VolumeCurved Aquarium Shapes
Bow Front
Bow front aquariums feature a gently curved front panel that adds visual depth and creates a panoramic viewing experience.
Calculate VolumeCylindrical
Cylindrical aquariums offer a 360-degree viewing experience and serve as striking centerpiece displays.
Calculate VolumeHalf Cylinder
Half cylinder aquariums feature a flat back panel that sits flush against a wall and a curved front that provides wide-angle viewing.
Calculate VolumeElliptical
Elliptical aquariums have an oval cross-section that produces a softer, more organic appearance than rectangular tanks.
Calculate VolumeBullnose
Bullnose aquariums have a rectangular body with one end replaced by a smooth half-cylinder curve.
Calculate VolumeRound End
Round end aquariums, also called stadium-shaped tanks, combine a rectangular center section with semicircular caps on both short ends.
Calculate VolumeFish Bowl
The classic fish bowl is a sphere, and calculating its volume requires the sphere formula.
Calculate VolumeCorner Aquarium Shapes
Corner Bow Front
Corner bow front aquariums combine the space-saving advantage of a corner placement with the elegant curved glass of a bow front design.
Calculate VolumeCorner Cylinder
Corner cylinder aquariums are quarter-circle tanks designed to tuck into a 90-degree room corner while presenting a curved viewing panel.
Calculate VolumeCorner
Corner aquariums are right-triangle prisms designed to fit snugly into a 90-degree room corner.
Calculate VolumePolygon Aquarium Shapes
Hexagonal
Hexagonal aquariums provide six flat viewing panels that give a near-360-degree experience while using flat glass that avoids optical distortion.
Calculate VolumeFlat Back Hexagon
Flat back hexagon aquariums are modified hex tanks with one flat rear panel designed to sit flush against a wall.
Calculate VolumeOctagon
Octagonal aquariums offer eight viewing panels that closely approximate a cylinder while using flat glass for distortion-free clarity.
Calculate VolumePentagon
Pentagon aquariums are five-sided tanks that offer an unusual geometric footprint, making them a conversation piece in any room.
Calculate VolumeCustom Aquarium Shapes
L-Shaped
L-shaped aquariums wrap around a corner or architectural feature using two joined rectangular sections that form an L when viewed from above.
Calculate VolumeTrapezoid
Trapezoid aquariums have a cross-section with two parallel sides of different lengths, creating a tapered profile that is wider at the front and narrower at the back (or vice versa).
Calculate VolumeHow Aquarium Shape Affects Volume
Two aquariums can occupy the same amount of floor space yet hold very different amounts of water. A rectangular tank and a bow front tank with identical back-panel dimensions differ in volume because the bow front's curved glass pushes outward, adding a half-ellipse of extra water. Similarly, a corner prism tank filling a 24 × 24-inch corner holds exactly half the water of a rectangular tank with the same footprint because the triangular cross-section eliminates half the area.
Polygon shapes like hexagons and octagons approximate circles, but the number of sides determines how much area the cross-section captures. A regular octagon inscribed in the same circle as a hexagon has a larger area — about 90% of the circle versus 83% for the hexagon. This means an octagon tank of the same outer diameter holds roughly 8% more water than a hexagon tank, a meaningful difference for stocking and filtration.
Curved tanks have predictable volume ratios between related shapes. A half cylinder always holds exactly half the water of a full cylinder with the same diameter and height because the flat back panel bisects the circular cross-section along the diameter; see the cylinder vs half cylinder aquarium volume comparison for the worked formulas and a side-by-side reference table.
Custom shapes such as L-shaped and trapezoid tanks require decomposing the footprint into simpler geometric primitives. An L-shaped tank is calculated as two separate rectangles added together, while a trapezoid uses the average of its two parallel bases multiplied by depth. Using the wrong formula — for example, treating a trapezoid as a rectangle using only the longer base — will overstate volume and lead to inaccurate chemical dosing, incorrect heater sizing, and unreliable stocking estimates.
Choosing the Correct Calculator
The fastest way to identify your tank shape is to look at it from directly above. A rectangular outline means you need the Rectangle, Cube, Breeder, or Shallow calculator depending on proportions. An oval or circular outline points to the Cylinder, Elliptical, or Fish Bowl calculator. If you see an L-shape, two joined rectangles, or a triangle in a corner, the specialized calculators for those shapes will give you the most accurate result.
When in doubt, measure the key dimensions and try the calculator that seems closest. Each calculator page includes a detailed measurement guide explaining exactly where to place your tape measure. If your tank is truly irregular and does not fit any of the 20 shapes offered here, you can break it into smaller sections, calculate each one separately using the appropriate formula, and add or subtract the results to arrive at a total volume.