Aquarium Glass Thickness Calculator: Front, End and Bottom Panels
Find the minimum glass thickness for a DIY aquarium’s front, end and bottom panels from its size and safety factor, with standard sheets and bowing.
How it works
t = √(β × H³ × 0.00001 ÷ (MOR ÷ SF)) in mm, with H = water height (mm), MOR = 19.2 N/mm² for annealed glass and SF = safety factor (3.8) · β from the panel ratio: front/back L/H, ends W/H (0.5 → 0.085, 0.666 → 0.1156, 1 → 0.16, 1.5 → 0.26, 2 → 0.32, 2.5 → 0.35, 3 → 0.37), bottom L/W (1 → 0.453, 1.5 → 0.5172, 2 → 0.5688, 2.5 → 0.6102, 3 → 0.7134) · Bowing = α × H⁵ × 0.00001 ÷ (69,000 × t³)
Water pushes on aquarium glass with a pressure that grows with depth, so the panels act like plates bending under load. The method used by hobby glass calculators treats each side panel as a plate held on three edges with a free top, and looks up a stress factor β from the panel’s length-to-height ratio: a long, low panel spreads the load to its ends less, so β rises up to the 3:1 limit of the table. Dividing the glass strength (19.2 MPa for ordinary annealed float glass) by a safety factor gives the stress the glass is allowed to carry; 3.8 is the figure most builders use for a braced tank. The calculator works out the minimum thickness for the front and back, the ends and the bottom (whose β comes from its length-to-width ratio), then rounds up to the next standard sheet: 6, 8, 10, 12, 15, 19 or 25 mm (about 1/4, 5/16, 3/8, 1/2, 5/8, 3/4 or 1 in). It also shows the water volume and weight, the glass weight, how much the front will bow when full, and the thickness at other safety factors. Limits: the formula assumes a full tank of fresh water, flat annealed glass, a level stand and good silicone seams. It does not design braces, overflows or drilled holes. Rimless tanks have no top frame, so many builders raise the safety factor to 5 or more. Unlike the aquarium volume calculator, which only gives gallons or liters, this one sizes the glass itself.
Worked example
A 48 × 18 × 24 in tank (1,219.2 × 457.2 × 609.6 mm) with a safety factor of 3.8: the allowed stress is 19.2 ÷ 3.8 = 5.053 N/mm². The front panel ratio is 48 ÷ 24 = 2.0, so β = 0.32 and t = √(0.32 × 609.6³ × 0.00001 ÷ 5.053) = 11.98 mm (0.47 in), so it needs 1/2 in (12 mm) glass. The ends have W/H = 0.75, β = 0.1268, t = 7.54 mm (0.30 in), so 5/16 in (8 mm). The bottom has L/W = 2.67, β = 0.6446, t = 17.00 mm (0.67 in), so 3/4 in (19 mm). The tank holds 89.8 US gal (340 L), about 748 lb (339 kg) of water, and 1/2 in glass bows about 0.40 mm in the middle of the front when full.
Sources: Glass thickness calculation for aquariums (β and α tables, 19.2 MPa, safety factor 3.8, worked 3,000 × 950 mm example) · Omni Calculator: Aquarium glass thickness (24 × 10 × 16 in and 20 × 10 × 23 in examples) · UKAPS forum: glass thickness and safety factors for braced and rimless tanks
Frequently asked questions
How thick should aquarium glass be?
It depends mostly on the water height and, less strongly, on the tank length. With a safety factor of 3.8, a 24 × 12 × 16 in (20 gal high) tank needs about 6 mm (1/4 in) glass, a 48 × 18 × 24 in tank needs about 12 mm (1/2 in) for the front and 19 mm (3/4 in) for the bottom, and tanks deeper than 30 in usually need 19 mm or more.
What safety factor should I use for a DIY aquarium?
3.8 is the standard figure for a braced tank made of annealed glass. Builders often increase it to 5 or more for rimless (frameless) tanks, unpolished edges or tanks that will be moved, which adds thickness. A lower factor saves glass but leaves less margin for flaws and scratches.
Why does height matter more than length?
Water pressure rises with depth and the bending load acts over the panel’s height, so thickness grows with height to the power 1.5: doubling the height nearly triples the required thickness. Making a tank longer only raises the β factor up to the table’s 3:1 limit.
Does the bottom glass need to be thicker than the sides?
Usually yes. The bottom carries the full water pressure across its whole area, so this method gives it a larger β than the front panel. On a tank that sits fully supported on a flat stand, some builders use the same thickness, but the calculator shows the conservative figure.
Can I use tempered glass for an aquarium?
Tempered glass is about four to five times stronger, but it cannot be cut or drilled after tempering, and it shatters completely if damaged. Most DIY builders use annealed float glass or laminated glass for the bottom. Use the glass strength option only with the supplier’s rating.
Related calculators
A planning estimate only. Glass quality, edge finish, seams and support all affect strength; have a large or tall tank checked by a glass supplier or engineer.