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Aquarium Glass Thickness Calculator
Aquarium Glass Thickness Calculator — Minimum Safe Thickness
Choosing the correct glass or acrylic thickness for a custom aquarium is a structural safety question — not an aesthetic one. Under-thickness glass can bow, crack, or fail catastrophically under the hydrostatic pressure of a full water column. The risk increases with tank height (water pressure increases with depth), tank length (longer unsupported spans bow more), and whether the tank has bracing across the top. The critical dimension is the aspect ratio of height to the unsupported span length of the largest panel. Professional aquarium manufacturers use engineering formulas based on glass modulus of rupture and a safety factor of 3.8 (meaning the glass is designed to fail at 3.8× the expected working stress). This calculator provides minimum recommended thickness for standard rectangular aquariums made of float glass or acrylic (PMMA). For unusually tall tanks, very large displays, or structural concerns, always consult a glazier or structural engineer.
How to Use This Calculator
1
Enter the length of the longest panel in centimeters — this is usually the front/back panel.
2
Enter the tank height — this determines the water pressure the glass must withstand.
3
Select float glass (standard) or acrylic. Acrylic is lighter and won't shatter but scratches easier.
4
Select whether the tank will have a top brace. Bracing significantly reduces required thickness on long tanks.
5
Build with the recommended thickness (one size up from minimum) for a proper safety margin.
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Frequently Asked Questions
What is the difference between float glass and low-iron glass?
Both are structurally equivalent for aquarium use — the thickness recommendations apply to either. Low-iron (ultra-clear/Starphire) glass has less green tint for better aesthetics but is not stronger. Use standard float glass thickness tables for both.
Why is height more important than length for glass thickness?
Water pressure increases with depth. The glass panel at the bottom of a 30-inch deep tank experiences 3× the pressure compared to the top of the same panel. Height determines the maximum hydrostatic stress; length determines the bending span. Both matter, but height usually drives thickness requirements.
Can I use tempered glass for all panels?
Tempered glass is 4–5× stronger than annealed glass of the same thickness, meaning you can use thinner panels. However, tempered glass cannot be cut or drilled after tempering — order it exactly sized with any bulkhead holes pre-drilled. Non-tempered glass is more flexible (literally — it can flex slightly under pressure without cracking) and is used for most display panels.
Is acrylic better than glass for aquariums?
Acrylic is lighter, stronger pound-for-pound, and can be cast into curved shapes. It scratches easily (though can be buffed). Glass is heavier, does not scratch from acrylic-safe tools, and doesn't yellow over time. Most high-end custom tanks over 200 gallons use acrylic; standard display tanks use glass.
