Free aquarium calculator
Aquarium Glass Thickness Calculator
Find the minimum glass thickness for each pane of a rectangular aquarium from its length, width and water height, rounded up to a real stock sheet size.
Use the full tank height unless you will always fill lower — water pressure depends on depth.
3.8 is the long-standing standard for aquarium glass. Choose a higher factor for tanks in busy areas, with children around, or when you want extra peace of mind.
Recommended thickness
Front & back panes
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This tank is over 60 cm (24 in) tall. Add a euro-brace or top bracing, and have the design checked by a professional glass supplier before building.
Enter length, width and water height to get a recommendation.
See the weight of this tank →For unbraced (rimless) tanks of plain annealed float glass. Braced or framed tanks can use thinner glass. This is a planning guide, not an engineering certification. Always confirm a custom build with your glass supplier.
How the glass thickness calculator works
Enter the inside length and width of your tank and the height of the water, then choose a safety factor. The calculator treats each upright pane as a sheet of glass held along its base and two sides, with the top edge free, and works out the thickness needed to keep the bending stress from water pressure safely below the strength of the glass. It reports a calculated minimum for the front and back panes and for the end panes, rounds each up to the next stock sheet size (4, 5, 6, 8, 10, 12, 15, 19 or 25 mm), and recommends a base at least as thick as the thickest upright pane.
The formula
Thickness = √(β × γ × H³ × SF ÷ σ). H is the water height, γ is the weight of water (9.81 × 10⁻⁶ N/mm³), σ is the modulus of rupture of float glass (19.2 N/mm²), and SF is the safety factor, 3.8 by default. β is a bending coefficient that depends on the pane's shape: it rises from 0.085 for a pane twice as tall as it is long to 0.37 for a pane three or more times longer than it is tall. Because height is cubed inside a square root, thickness grows with height to the power of 1.5. Double the height of a tank and it needs roughly 2.8 times thicker glass, while doubling the length at the same height adds far less.
Worked example
A rimless 120 × 45 × 50 cm tank has a front pane 2.4 times longer than it is tall, giving β ≈ 0.344. With 500 mm of water the calculation is √(0.344 × 9.81 × 10⁻⁶ × 500³ × 3.8 ÷ 19.2) ≈ 9.1 mm, so the front and back need 10 mm glass. The 45 cm end panes have a ratio of 0.9 and work out at about 6.0 mm, so 6 mm glass is enough, and the base should be 10 mm. Most builders would still use 10 mm all round for a uniform look and simpler silicone joints.
Rimless, braced and framed tanks
The calculator assumes an unbraced, rimless tank, which is the most demanding case. A plastic frame or a glass euro-brace around the top edge supports the panes so they bend less, which is why mass-produced framed tanks often use thinner glass than these figures. A typical 55-gallon framed tank, for example, uses about 6 mm glass with a center brace, where a rimless version of the same size needs about 10 mm. Never remove the frame or brace from an existing tank. It is part of the structure, and the glass may not be thick enough without it.
Glass thickness chart for common tank sizes
Recommended thickness for rimless tanks filled to the top, at the standard 3.8 safety factor. Sizes are length × width × height in centimeters.
| Tank size (cm) | Front & back panes | End panes | Base |
|---|---|---|---|
| 45 × 30 × 30 | 4 mm | 4 mm | 4 mm |
| 60 × 30 × 36 | 6 mm | 4 mm | 6 mm |
| 80 × 35 × 40 | 8 mm | 5 mm | 8 mm |
| 90 × 45 × 45 | 8 mm | 6 mm | 8 mm |
| 100 × 40 × 50 | 10 mm | 6 mm | 10 mm |
| 120 × 45 × 50 | 10 mm | 6 mm | 10 mm |
| 150 × 50 × 60 | 15 mm | 8 mm | 15 mm |
| 180 × 60 × 60 | 15 mm | 10 mm | 15 mm |
Frequently asked questions
- How thick should aquarium glass be?
- It depends mainly on the water height and, to a lesser degree, the length of each pane. As a guide for rimless tanks: up to 30 cm (12 in) tall, 4–5 mm; 40 cm (16 in), 6–8 mm; 50 cm (20 in), 10 mm; 60 cm (24 in), 12–15 mm. Enter your exact dimensions in the calculator for a pane-by-pane recommendation.
- Why does height matter more than volume?
- Water pressure increases with depth, not with the amount of water. At 50 cm deep the pressure on the glass is about 4.9 kPa whatever the length of the tank. The bending load on a pane grows with the cube of its height, so a tall, narrow tank can need thicker glass than a long, shallow tank holding twice the water.
- What safety factor should I use?
- A safety factor of 3.8 is the long-established standard for aquarium glass and allows for flaws in the glass, scratches, uneven stands and the long-term fatigue of a pane under constant load. Use a higher factor if the tank is in a busy area, with children or pets around, or if you simply want a larger margin.
- Should the base be thicker than the sides?
- The base should be at least as thick as the thickest upright pane. On a properly level stand with a foam leveling mat or a full support the base is evenly loaded. On tanks supported only around the edges, or larger tanks, many builders go one size thicker on the base for extra stiffness.
- Can I use this for acrylic tanks?
- No. Acrylic is far more flexible than glass and has a different strength, so it needs its own calculation and is usually specified by the manufacturer. This calculator is for annealed float glass. Low-iron (ultra-clear) glass has practically the same strength as standard float glass, so the same figures apply.