How do I calculate volume for custom shaped tanks like cylinders or hex tanks?

For cylinder tanks, multiply Pi (3.14159) by the squared radius, then multiply by height and divide by 231. For hexagon tanks, multiply the bottom hexagon area by height and divide by 231.

Why does my 55 gallon tank hold only 48 gallons of actual water?

Advertised tank sizes measure external glass dimensions. Internal glass thickness, substrate bed depth, and leaving a 1-inch air gap at the top reduce actual water capacity by 10% to 15%.

Aquarium Volume Target

Aquarium Volume Calculator

Find out exact US gallons, liters, and water weight for any custom or standard fish tank dimensions.

Step 1

Select Aquarium Geometry

Step 2

Input Dimensions & Substrate

Quick Size Preset

Length Inches

Width Inches

Height Inches

Substrate Bed Depth (Gravel / Sand)

Standard community tanks use 2 inches (5 cm) of gravel or aquasoil.

Rectangular Tank 30" x 12" x 12"

3D visual mockup updates dynamically to your selected tank shape.

Step 3 • Hydro Calculation Output

Water Volume

0 Gallons

(0 Liters)

Filled Tank Weight

0 lbs

(0 kg)

Gravel / Sand Needed

0 lbs

(0 kg)

Specs & Stocking

Filter GPH: 0 GPH

Heater Power: 0 Watts

Max Fish Length: 0 in