What glass thickness does a 60cm tank need?

A 600×300×360 60P uses 6mm low-iron glass. A 600×400×400 standard tank runs at about 385mm of water, where 6mm is still enough; if it is rimless and you want more margin, go to 8mm.

How thick should a 90cm tank be?

A 900×450×450 runs at about 425mm of water: 8mm is recommended for a rimless tank, and 8mm is adequate with bracing; above 500mm in height, 10mm is advisable.

How thick does a 120cm tank need to be?

A 1200×500×500 runs at about 475mm of water: 12mm is recommended for a rimless tank, and the base pane is automatically thickened to 15mm for the span; with bracing you can drop to 10mm.

Why is the base pane thicker than the sides?

The base carries the entire water volume plus the substrate and hardscape, and it has to stay perfectly flat with no flex, so it is normally at least as thick as the sides and goes one step thicker once the span exceeds 800mm.

Does low-iron glass break more easily than ordinary glass?

Low-iron glass has a flexural strength close to ordinary float glass; the difference is mainly iron content and light transmission. The real risks come from how flat the glass is and the quality of the cutting, edge polishing and silicone work.

C-01

Glass Thickness

Glass thickness is not driven by overall tank height but by water height (tank height − water gap). Two tanks of the same 500mm height, one with a 15mm gap and one with a 50mm gap, can need thicknesses a whole step apart.

Choose aquarium glass thickness by water height: a rimless tank at 450mm needs 8mm, and bracing brings that down to 6mm.

Units

Input parameters

Tank body height H

Water gap below rim

Tank long edge (used to thicken the bottom)

Bracing style

Comparison of the two cases

Recommended side thickness: 0.31 in (≈ 5/16")
Recommended bottom thickness: 0.39 in (≈ 3/8")
Water level: 17.13 in
Height-to-thickness ratio (water level ÷ thickness): 54.4 / limit 67.8

Case	Thickness needed
Rimless (no bracing)	0.31 in
Braced / framed	0.24 in

A rimless tank has no upper bracing to share the water pressure, so the height-to-thickness limit is lower (the curve drops from about 80 to 30), and the same size therefore needs thicker glass. The bottom panel carries the water and the substrate, must be absolutely flat, and is usually no thinner than the sides, thickened by 1~2 steps according to the span.

Safety note: the curves are calibrated against common ready-made tank setups; actual strength depends on glass quality (float / low-iron), flatness, silicone workmanship, and the flatness of the base mat and floor. For large tanks, ask a professional shop to review the design.

The calculator above follows the unit system selected at the top of this page; the explanatory text below stays metric (mm / L / kg / ℃).

Need a full design?

Want to turn the dimensions into a 3D model and a complete bill of materials: Enter length, width and height in the aquarium designer and it generates the 3D model, dimensions, glass cut list, silicone usage and equipment selection, all exportable as CSV and PNG.

How to use it

Step 1Measure tank height and water gapThe water gap is the distance from the water surface to the rim, usually 10~30mm; on a sump tank, use the overflow-set water level.
Step 2Decide the bracingRimless / low-iron with no bracing, or with top bracing, a frame or edge trim. Bracing raises the safe span-to-height ratio substantially.
Step 3Read off side and base thicknessThe sides take the next standard step on the span-to-height curve; the base pane then goes 1~2 steps thicker for the span.

Frequently asked questions

What glass thickness does a 60cm tank need?: A 600×300×360 60P uses 6mm low-iron glass. A 600×400×400 standard tank runs at about 385mm of water, where 6mm is still enough; if it is rimless and you want more margin, go to 8mm.
How thick should a 90cm tank be?: A 900×450×450 runs at about 425mm of water: 8mm is recommended for a rimless tank, and 8mm is adequate with bracing; above 500mm in height, 10mm is advisable.
How thick does a 120cm tank need to be?: A 1200×500×500 runs at about 475mm of water: 12mm is recommended for a rimless tank, and the base pane is automatically thickened to 15mm for the span; with bracing you can drop to 10mm.
Why is the base pane thicker than the sides?: The base carries the entire water volume plus the substrate and hardscape, and it has to stay perfectly flat with no flex, so it is normally at least as thick as the sides and goes one step thicker once the span exceeds 800mm.
Does low-iron glass break more easily than ordinary glass?: Low-iron glass has a flexural strength close to ordinary float glass; the difference is mainly iron content and light transmission. The real risks come from how flat the glass is and the quality of the cutting, edge polishing and silicone work.