Aquarium Volume & Glass Thickness Calculator.

Measure the internal length, width, and height of your tank in centimetres, then use the formula: Volume (litres) = L × W × H ÷ 1000. For non-rectangular shapes such as bowfront or hexagonal tanks, our aquarium calculator adjusts the base-area formula automatically. Subtract substrate displacement (gravel or sand depth × base area) to get the net water volume available for fish and filtration.

Enter your tank's length, width, and height into the fish tank gallon calculator. The tool computes gross volume in litres first, then converts: 1 US gallon = 3.785 L. A standard 60 × 30 × 36 cm tank is approximately 65 litres or 17.2 US gallons. Remember that substrate and decorations reduce this figure by 10–20% in a planted setup.

Always measure the inside (interior) dimensions. Glass panels add 6–19 mm per side depending on thickness. Measuring exterior dimensions and then subtracting twice the glass thickness for each dimension gives the true water volume. Our calculator includes a glass-offset field that performs this correction automatically.

For a bow-front aquarium, the calculator uses the trapezoid approximation: base area = ((front width + back width) / 2) × depth. For a hexagonal prism tank, the formula is: base area = (3√3 / 2) × s², where s is the flat-to-flat width divided by √3. Select the matching shape in our aquarium size chart calculator and enter the requested dimensions — the correct formula is applied automatically.

Manufacturers state gross nominal volume measured from outside edges at full depth. In practice, glass thickness, substrate (gravel or sand), rocks, driftwood, filter equipment, and an air gap below the waterline all displace water. A well-planted 100-litre (26 gal) aquarium may hold only 70–80 litres of actual water. Use our fish tank water capacity calculator with the substrate offset to get the true net volume.

For a rectangular aquarium, multiply Length × Width × Height (in cm) and divide by 1,000 to get volume in litres. To convert litres to US gallons, multiply by 0.264172 (or divide cubic inches by 231).

Gross volume is the maximum external capacity of the empty glass shell. Net water volume is the actual amount of liquid in the tank after accounting for glass thickness, the top headroom gap (~1 cm fill line), and displacement from substrate and rocks.

For a bowfront tank, calculate the rectangular base area plus the parabolic curve area: (L × W) + (2/3 × L × bow depth) multiplied by height. For a cylinder tank, use π × radius² × height.

Glass thickness for aquariums is calculated using the plate-bending formula: t = √(SP × h² / (0.75 × E)), where SP is water pressure, h is the longest unsupported panel height, and E is the allowable bending stress for glass (~19 MPa with a safety factor of 3.8). Our aquarium glass thickness calculator outputs the minimum recommended thickness in millimetres, then rounds up to the nearest standard glass size (4, 5, 6, 8, 10, 12, 15, 19 mm).

The safety factor divides the allowable bending stress used in the thickness formula. A factor of 3.8 is the DIY and rimless standard (recommended default). Use 4.0 for extra conservatism on large rimless builds, 3.0 for fully braced Euro-brace tanks, and 2.5 only for smaller braced tanks where deflection is mechanically constrained. A higher safety factor results in a thicker — and safer — glass recommendation.

Yes. Without a top frame or cross-brace to distribute hydrostatic pressure, each glass panel in a rimless build bears the full bending load from water. Our how thick glass for aquarium calculator automatically applies the higher safety factor of 3.8–4.0 for rimless builds versus 2.5–3.0 for braced tanks, which typically results in 2–4 mm thicker panels for the same tank dimensions.

Acrylic deflection is calculated using the same plate-bending equations, but with acrylic's Young's modulus (~3 GPa vs. glass's ~70 GPa). This means acrylic flexes significantly more for the same thickness. Our calculator outputs the expected panel deflection (bow) in millimetres. For acrylic tanks, the maximum recommended deflection is L/250, where L is the panel's long edge, to avoid permanent deformation or silicone joint stress.

Glass thickness depends on water height and panel length. For a standard 60 cm long by 36 cm high rimless tank, 6 mm float glass with a safety factor of 3.8 is standard. Taller tanks (over 50 cm) require 10 mm to 12 mm glass to prevent bowing deflection and failure.