Shape guide

Aquarium Shapes

Look at your tank from above and match the footprint. Each entry describes the shape in a sentence and links to its calculator.

Standard Tanks

Standard tanks are rectangular prisms: four vertical walls at right angles and a flat floor. They include the everyday framed tank, the rimless cube, the wide breeder and the low shallow tank. All four use the same formula, but each has its own proportions, typical sizes and measurement pitfalls.

Rectangular standard tank · box tank

The rectangular tank is the baseline every other aquarium shape is compared against.

Needs: Length, Width, Height

Calculate rectangular volume →

Cube cube tank · rimless cube

Cube aquariums have equal length, width and height, so a single measurement is enough to find the volume.

Needs: Side Length

Calculate cube volume →

Breeder 40 breeder · breeder tank

Breeder tanks are rectangular aquariums with a much wider front-to-back footprint than standard tanks of the same length.

Needs: Length, Width (front to back), Height

Calculate breeder volume →

Shallow shallow rimless · low tank

Shallow aquariums put a large footprint under a low water column.

Needs: Length, Width, Height

Calculate shallow volume →

Curved Tanks

Curved tanks have at least one panel that is not flat. Cylinders and bowls are fully round, while bow fronts, bullnose and round end tanks combine straight sections with arcs. Each needs a formula that includes π somewhere, and each has a measurement that is easy to take in the wrong place.

Bow Front bowfront tank · curved front aquarium

A bow front aquarium has a flat back and sides with a front panel that curves outward.

Needs: Length, Flat Depth, Bow Depth, Height

Calculate bow front volume →

Cylinder column tank · tube aquarium

Cylindrical aquariums range from desktop acrylic columns to floor-to-ceiling tower tanks.

Needs: Radius, Height

Calculate cylinder volume →

Half Cylinder D-shaped tank · semi-circular tank

A half cylinder aquarium has a flat back panel and a semicircular front, forming a D shape when viewed from above.

Needs: Radius, Height

Calculate half cylinder volume →

Elliptical oval tank · oval column

Elliptical aquariums have an oval footprint, usually seen in acrylic columns and some designer desktop tanks.

Needs: Semi-Major Axis (a), Semi-Minor Axis (b), Height

Calculate elliptical volume →

Bullnose single round end · peninsula tank

A bullnose aquarium is a rectangular tank with one end replaced by a semicircle.

Needs: Overall Length, Width, Bullnose Radius, Height

Calculate bullnose volume →

Round End stadium tank · capsule tank

Round end aquariums have a stadium or capsule footprint: a rectangle with a semicircle on each end.

Needs: Overall Length, Width, Height

Calculate round end volume →

Fish Bowl goldfish bowl · globe tank

A fish bowl is approximately a sphere, so a single diameter measurement gives the full volume.

Needs: Diameter

Calculate fish bowl volume →

Corner Tanks

Corner tanks have two straight panels that meet at a right angle so the tank can sit against two walls. What differs is the front: a flat panel makes a corner prism, a shallow curve makes a corner bow front and a full quarter-circle arc makes a corner cylinder.

Corner Bow Front corner curved tank · corner panorama

A corner bow front sits in a 90-degree room corner with two flat sides against the walls and a curved front panel facing the room.

Needs: Front Span, Bow Depth, Height

Calculate corner bow front volume →

Corner Cylinder quarter cylinder · quarter round tank

A corner cylinder tank is a quarter of a cylinder: two straight panels meet at a right angle against the room corner and a curved front panel joins their outer ends.

Needs: Radius, Height

Calculate corner cylinder volume →

Corner Prism triangular corner tank · corner triangle

A corner prism aquarium has a right-triangle footprint: two panels meet at 90 degrees against the walls and a single flat front panel closes the triangle.

Needs: Leg 1 (wall side), Leg 2 (wall side), Height

Calculate corner prism volume →

Polygon Tanks

Polygon tanks are built from flat panels arranged around a centre. Regular polygons have equal sides and need only one panel width plus the height. The flat back hexagon is the important exception: six sides, but a long back panel and short sides for wall placement.

Hexagon hex tank · six-sided tank

Hexagonal aquariums have six equal glass panels and are often built tall, which gives a strong vertical display in a small footprint.

Needs: Side Length, Height

Calculate hexagon volume →

Flat-Back Hexagon flat back hex · half hex

A flat back hexagon has a straight back panel for wall placement, two short straight sides, two angled panels and a front panel: six sides, but not a regular hexagon.

Needs: Back Length, Overall Depth, Front Panel Width, Straight Side Panel Length, Height

Calculate flat-back hexagon volume →

Octagon octagonal tank · eight-sided column

Octagonal aquariums have eight equal panels and come closer to a cylinder than a hexagon does, while still using flat glass.

Needs: Side Length, Height

Calculate octagon volume →

Pentagon five-sided tank · pentagonal column

Pentagonal aquariums are uncommon but distinctive.

Needs: Side Length, Height

Calculate pentagon volume →

Custom Shapes

Custom tanks are built to fit a space rather than a catalogue. Most can be broken into rectangles, triangles and arcs. The L-shaped and trapezoid calculators cover the two most common custom footprints, and almost any other layout can be assembled from them plus the standard shapes.

L-Shaped L tank · wrap-around tank

L-shaped aquariums wrap around a room corner or a structural column.

Needs: Section 1 Length, Section 1 Width, Section 2 Length, Section 2 Width, Height

Calculate l-shaped volume →

Trapezoid tapered tank · wedge tank

Trapezoid aquariums have a front and back panel of different widths joined by angled sides.

Needs: Front Base, Back Base, Depth (front to back), Height

Calculate trapezoid volume →

How shape affects volume

Two tanks with the same width across and the same height can differ by half their volume depending on footprint. A circle fills 78.5 percent of the square that contains it, a hexagon 65 percent, a right triangle 50 percent. Curved fronts add a few percent over the equivalent box; cut corners remove a few. That is why picking the right calculator matters more than measuring to the last millimetre.

Still not sure?

Ask three questions. Is any panel curved? Do two sides meet at a right angle so the tank sits in a corner? Are all the panels the same width? Flat, not corner, not equal: rectangular or trapezoid. Curved: bow front, cylinder family, bullnose or round end. Corner: corner prism, corner bow front or corner cylinder. Equal panels: hexagon, octagon or pentagon. If none fit, send us a sketch.