Toughened Glass Weight Chart: kg per Sq Ft and per Sq Metre

Glass weight comes from one number: density. Soda-lime float glass, the glass that gets toughened for railings, has a density of about 2,500 kg per cubic metre. That works out to 2.5 kg per square metre for every millimetre of thickness, and every figure below follows from it.

Toughened glass weight chart

Toughened, heat-strengthened and ordinary annealed glass of the same thickness all weigh the same. Toughening is a heat treatment that changes strength and the way the pane breaks, not its mass. The difference between the types is covered in toughened vs laminated glass.

The glass weight formula

You do not need a calculator app. Two versions of the same formula cover every case:

• Metric: weight (kg) = width (m) × height (m) × thickness (mm) × 2.5
• Feet: weight (kg) = width (ft) × height (ft) × thickness (mm) × 0.232

The 0.232 is simply 2.5 divided by 10.764, the number of square feet in a square metre. For a quick mental check, 12 mm glass is a little under 3 kg per square foot and 10 mm is a little under 2.5 kg.

Two worked examples

Example 1, in millimetres. A balcony panel 1,200 mm wide and 1,000 mm high in 12 mm toughened glass. Area = 1.2 × 1.0 = 1.2 m². Weight = 1.2 × 12 × 2.5 = 36 kg.

Example 2, in feet. A panel 4 ft wide and 3.5 ft high in 12 mm toughened glass. Area = 14 sq ft. Weight = 14 × 12 × 0.232 = about 39 kg.

For a whole run, multiply by the number of panels, or work per running length: 12 mm glass standing 1 metre high weighs 30 kg per running metre, which is about 9 kg per running foot. That is the glass only. Channels, spigots, brackets and the top handrail are extra and depend on the system chosen.

How laminated glass adds up

Laminated glass is two or more panes bonded with a plastic interlayer. Its weight is the sum of the glass plies plus a small amount for the interlayer. A 1.52 mm PVB interlayer adds roughly 1.6 kg per square metre, because the plastic is less than half as dense as glass.

• 13.52 mm (6 + 1.52 + 6): 12 mm of glass = 30 kg, plus interlayer = about 31.6 kg/m², or 2.94 kg per sq ft.
• 17.52 mm (8 + 1.52 + 8): 16 mm of glass = 40 kg, plus interlayer = about 41.6 kg/m², or 3.86 kg per sq ft.
• 21.52 mm (10 + 1.52 + 10): 20 mm of glass = 50 kg, plus interlayer = about 51.6 kg/m², or 4.79 kg per sq ft.

So the 17.5 mm laminated panel used on taller balustrades is nearly 40% heavier than a 12 mm toughened panel of the same size. If you only know the nominal thickness and not the build-up, multiplying the full thickness by 2.5 gives a slightly high figure, which is the safe direction for planning a lift.

Why the weight matters

• Handling. A 36 to 40 kg panel is a two-person lift with suction lifters, and it has to get up the staircase or go over the edge on ropes. Toughened glass is most vulnerable at its edges and corners, so panels are rested on timber or rubber, never directly on concrete or tile. Panel size is fixed before toughening, as explained in cutting and drilling toughened glass, so decide what can physically be carried to the floor before ordering.
• Fixings. A continuous channel carries the panel along its whole bottom edge. Spigots and point brackets carry the same dead weight on a few points, and with side-mounted fixings the anchors hold that weight in shear on the slab face. The system has to be one that is made for the glass thickness you are using.
• Slab load. A glass balustrade is far lighter than a masonry parapet of the same height, so dead weight is rarely what worries the structural engineer. The larger demand is the horizontal load from people leaning on the barrier, which the glass passes to the base and its anchors as leverage. Our anchors and fixings guide covers that side. Where dead weight really is the constraint, wire infill is lighter; see cable railing vs glass railing.
• Transport. Glass is priced by area but freighted by weight. A run of 20 panels like Example 1 is 720 kg before crating.

Weight does not decide the thickness

Choose the thickness for the railing height and location first, then use this chart to plan handling and fixings. Which thickness suits which supported height, and where laminated glass is the right specification, is set out in our glass railing thickness guide.

If you send the run length, finished height and location, we will suggest the system and glass specification to match. Contact Prince Railing with your drawing or site photos.