Aquarium Glass Thickness Calculator
Planning a DIY or rimless tank? Estimate how thick the front, end and bottom glass should be, rounded up to the next standard glass size.
How to use this calculator
- Enter the outside length, width and height of the tank you plan to build. The calculator assumes the tank is filled to the top, which is the worst case.
- Keep the safety factor at 3.8 unless you have a reason to change it. Raise it for tall or rimless display tanks.
- Read the minimum thickness for each panel, then the standard glass size it rounds up to. Most builders use the thickest wall figure for all four walls so the joints line up.
- Check the bow figure. It shows how far the middle of the front panel pushes outward under full water pressure at the recommended thickness. A fraction of a millimeter is normal.
How the glass thickness is calculated
This calculator uses the plate bending method that has been the standard in the fishkeeping hobby for years, and is the same approach used by most online glass calculators. Each wall is treated as a flat glass plate held along the bottom and both sides, with the top edge free (no rim or brace). Water pushes on it with a pressure that grows with depth.
- H is the water height in millimeters.
- 0.00001 is the weight of water in N/mm³ (density × gravity, with gravity rounded up to 10 m/s², which adds a small extra margin).
- 19.2 N/mm² (MPa) is the long-term tensile strength used for ordinary annealed float glass.
- SF is the safety factor. At 3.8 the glass is only allowed to reach about 5.05 N/mm² of bending stress.
- β (beta) is a plate coefficient that depends on the panel's shape (its length divided by its height). A long, low panel bends more in the middle than a narrow one, so it gets a higher β.
The bottom panel uses the same formula with a β taken from a second table, based on the tank's length divided by its width. The front panel bow (deflection) is estimated with a matching α coefficient and a glass stiffness of 69,000 N/mm²:
Values between table rows are interpolated in a straight line. Ratios below the first row use the first row, and ratios above 3 use the last row.
Plate coefficients used
| Wall ratio (L ÷ H) | α | β |
|---|---|---|
| 0.5 | 0.003 | 0.085 |
| 1.0 | 0.022 | 0.160 |
| 1.5 | 0.042 | 0.260 |
| 2.0 | 0.056 | 0.320 |
| 2.5 | 0.063 | 0.350 |
| 3.0 | 0.067 | 0.370 |
| Bottom ratio (L ÷ W) | α | β |
|---|---|---|
| 1.0 | 0.0770 | 0.4530 |
| 1.5 | 0.0906 | 0.5172 |
| 2.0 | 0.1017 | 0.5688 |
| 2.5 | 0.1110 | 0.6102 |
| 3.0 | 0.1335 | 0.7134 |
A note on the bottom table: published versions of it differ slightly between sources, and it is applied with the water height rather than the tank width. That makes the bottom figure conservative (thicker) compared with a strict plate calculation, which is a reasonable choice because real bottoms also face uneven stands and point loads from rock.
Worked example: a rimless 55 gallon (48 × 13 × 21 in)
Water height H = 21 in = 533.4 mm. The front panel ratio is 48 ÷ 21 = 2.29, which falls between the 2.0 and 2.5 rows, so β ≈ 0.337.
t = √(0.337 × 533.4³ × 0.00001 ÷ 5.05) ≈ 10.1 mm, which rounds up to 12 mm glass. At 12 mm the front panel bows about 0.22 mm in the middle.
The end panels (ratio 13 ÷ 21 = 0.62) need about 5.6 mm, so 6 mm. The bottom (ratio 48 ÷ 13 = 3.7, capped at 3.0) comes out at about 14.6 mm, so 15 mm.
A store-bought 55 gallon tank usually has 1/4 in (6 mm) walls. It gets away with that because its plastic rim and center brace hold the top edge in place. Take the rim off and you would need much thicker glass, which is why rimless tanks are built from heavier glass.
Standard glass thicknesses
| Metric | Nearest US size | Typical use |
|---|---|---|
| 4 to 5 mm | 5/32 to 3/16 in | Small nano tanks |
| 6 mm | 1/4 in | Small to medium tanks |
| 8 mm | 5/16 in | Medium tanks |
| 10 mm | 3/8 in | Medium to large tanks |
| 12 mm | 1/2 in | Large and rimless tanks |
| 15 mm | 5/8 in | Large tanks and bottoms |
| 19 mm | 3/4 in | Very large tanks |
| 25 mm | 1 in | Very large tanks (professional design) |
Frequently asked questions
Why does the calculator say thicker glass than my store-bought tank uses?
Most mass-produced tanks have a plastic rim and often a center brace. These hold the top edge of the glass so it cannot bow outward, which lets the maker use thinner glass. This calculator assumes a rimless tank with a free top edge, which is the more demanding case.
What safety factor should I use for aquarium glass?
A safety factor of 3.8 is the long-standing default used by hobby glass calculators. Many builders go higher for rimless display tanks, tall tanks or tanks in places where a failure would be dangerous or very costly.
Does tank length or height matter more?
Height matters far more. Water pressure grows with depth, and the required thickness rises roughly with the height to the power of 1.5. Doubling the height nearly triples the glass thickness, while making a tank longer only raises it a little.
Can I use tempered glass to go thinner?
Tempered glass is much stronger, but it cannot be cut or drilled after tempering and it shatters into small pieces if it fails. Most aquarium builders use annealed float glass for the walls. This calculator only covers annealed glass.
Is the bottom glass thickness important if the tank sits on a mat?
Yes. A level stand and a foam mat spread the load, but uneven stands, heavy rock and point loads still stress the bottom. The bottom panel figure here is a conservative hobby estimate, and the bottom should never be thinner than the walls.
Related calculators
- Aquarium volume calculator: gallons and liters for your planned tank
- Aquarium weight calculator: total weight of glass, water and substrate on your stand
Sources: Formula, glass strength (19.2 N/mm²), safety factor 3.8, modulus (69,000 N/mm²) and α/β tables from Aquarium World NZ, "Calculating Glass Thickness for Aquariums" and MonsterFishKeepers, "How to calculate the glass thickness for your aquarium". Results cross-checked against the Omni aquarium glass thickness calculator. Simplified strip method and standard sizes compared with calculate.co.nz.
Last updated: October 2026