One number you can do in your head
Every millimetre of glass weighs 2.5 kg per square metre. That is the whole calculation, and everything else on this page is a consequence of it.
It comes straight from the density. EN 572-1 — the European standard for basic soda-lime silicate glass — gives the density as 2500 kg/m³ for the purpose of calculation. A square metre one millimetre thick is 0.001 m³, and 0.001 × 2500 = 2.5 kg. Nothing is approximated.
So a 1200 × 800 mm pane of 6 mm glass: 0.96 m² × 15 kg/m² = 14.4 kg. The long way round gives the same answer — 1.2 × 0.8 × 0.006 = 0.00576 m³, times 2500 = 14.4 kg — and is worth doing once to see where the shortcut comes from.
Weight by thickness
| Thickness | kg per m² | lb per ft² |
|---|---|---|
| 3 mm | 7.5 | 1.54 |
| 4 mm | 10 | 2.05 |
| 5 mm | 12.5 | 2.56 |
| 6 mm | 15 | 3.07 |
| 6.35 mm (1/4″) | 15.88 | 3.25 |
| 8 mm | 20 | 4.10 |
| 9.525 mm (3/8″) | 23.81 | 4.88 |
| 10 mm | 25 | 5.12 |
| 12 mm | 30 | 6.14 |
| 12.7 mm (1/2″) | 31.75 | 6.50 |
| 19 mm | 47.5 | 9.73 |
In imperial the equivalent rule of thumb is 13 lb per square foot per inch of thickness, which is the same density expressed differently and is accurate to within a rounding.
6 mm is not quarter-inch glass
An inch is 25.4 mm exactly, so a quarter inch is 6.35 mm. Nominal 6 mm and nominal 1/4 inch are two different products that sit next to each other in a catalogue, and the difference is about 6% by weight: 15 against 15.88 kg/m².
On a small pane that is a rounding error. On a 2 × 3 metre shopfront it is five kilograms, which is enough to matter when the question is whether two people can carry it.
The other fractions, converted exactly: 1/8″ is 3.175 mm, 3/16″ is 4.7625 mm, 3/8″ is 9.525 mm, 1/2″ is 12.7 mm and 3/4″ is 19.05 mm — which is why 19 mm and 3/4 inch are treated as the same thing in practice and 6 mm and 1/4 inch are not.
What does not change the weight
Three things people reasonably expect to matter, and none of them does:
- Toughening. Tempering is a heat treatment that changes the stress distribution inside the glass. The composition and the density are untouched, so a toughened pane weighs exactly what an annealed one of the same dimensions weighs. Heat-strengthened glass is the same.
- Coatings. Low-emissivity and solar-control coatings are measured in nanometres. A 6 mm low-E pane and a 6 mm clear pane weigh the same to any scale you would use.
- Tint. Body-tinted glass is coloured by additives in the melt at concentrations too small to move the density measurably.
What does change it: the glass type itself. Borosilicate is around 2230 kg/m³ and so about 11% lighter than soda-lime. Lead crystal is far heavier. The density field on this page exists for those cases.
Laminated glass, and the mistake in the middle
A laminate is two or more plies of glass bonded to a plastic interlayer, usually PVB. The interlayer is not glass, and this is where calculations go wrong.
Take an 8.76 mm laminate: two 4 mm plies with a 0.76 mm interlayer. Treat the whole 8.76 mm as glass and you get 21.9 kg per square metre. Do it properly — 8 mm of glass at 2500 plus 0.76 mm of PVB at about 1070 — and you get 20.81 kg. The overstatement is about a kilogram per square metre, or 5%.
Common laminate builds and what they are made of:
| Nominal | Build | kg per m² |
|---|---|---|
| 6.4 mm | 3 + 0.38 PVB + 3 | 15.41 |
| 6.8 mm | 3 + 0.76 PVB + 3 | 15.81 |
| 8.76 mm | 4 + 0.76 PVB + 4 | 20.81 |
| 11.52 mm | 5 + 1.52 PVB + 5 | 26.63 |
| 13.52 mm | 6 + 1.52 PVB + 6 | 31.63 |
The layer builder above works these out for you, and lets you change the interlayer density where a product differs from the typical PVB figure.
Insulated units
Easier than laminates, because the cavity weighs nothing.
A 4-16-4 unit — two 4 mm panes separated by a 16 mm cavity — is 24 mm thick and weighs exactly what 8 mm of glass weighs: 20 kg per square metre. Air is 1.2 kg/m³ and argon is 1.8, which over a 16 mm gap comes to about 20 or 30 grams per square metre — less than the error in your tape measure.
The spacer bar, the desiccant and the sealant are real but they run round the perimeter rather than over the area, so they scale with the frame rather than with the glass and are usually accounted for separately by the fabricator.
Mark the cavity as a cavity in the layer builder and it is counted in the overall thickness and excluded from the weight, which is what the fabrication drawing does too.
What this page will not tell you
It gives you a weight. It does not tell you whether that weight is safe to lift, or whether a bracket, a frame or a shelf can carry it.
Handling is not a function of mass alone. A 30 kg pane two metres across is awkward, flexible and fragile in ways that a 30 kg box is not, and the grip you can get on it matters as much as the number. Manual handling guidance differs by country and by workplace, and glazing has its own practices — suction cups, A-frames, two people on the long edge — that exist because the shape is the problem.
The same goes for structure. A shelf, a balustrade or a rooflight is specified by someone who knows the fixings, the span and the loads it will see. The weight from this page is an input to that conversation, not a substitute for it.
Circles, and anything that is not a rectangle
The calculator takes a length and a width, which covers most glass. For a shape that is not a rectangle, work out the area yourself and enter it as a square of the same area — the weight depends only on the area, never on the outline.
A circle is πr². A 600 mm round table top is π × 0.3² = 0.2827 m², so at 10 mm it weighs 0.2827 × 25 = 7.07 kg. The 600 × 600 mm square it was cut from weighed 9 kg, and the difference — just under 2 kg — is the offcut.
That gap is worth knowing for a different reason too: a glazier will usually charge for the rectangle, because that is the sheet consumed, while you will only carry the circle. Cost scales with the enclosing rectangle; weight scales with the actual shape.
For a genuinely irregular outline, split it into rectangles and triangles, add the areas and treat the total as one square. A triangle is half its base times its height, so a triangular shelf 800 mm along the wall and 400 mm deep is 0.16 m² — the same weight as a 400 × 400 mm square of the same glass.
What a glazier needs from you
Weight is one of five things, and the other four are the ones that cause remakes.
- Size, and how it was measured. A tight fit needs a tolerance; glass does not compress. Most glaziers work to a small deduction off the aperture, and they need to know whether your figures are the aperture or the glass.
- Thickness. Say 6 mm or say 1/4 inch, and mean it — they are different products, about 6% apart by weight, and a supplier will cut what you asked for.
- Toughened or annealed. This does not change the weight at all, but it changes everything else: toughened glass cannot be cut, drilled or edged after treatment, so every hole and every notch has to be specified before it goes in the furnace.
- Edgework. A cut edge is sharp and fragile; a polished or arrissed edge is neither. Any edge anyone can touch needs finishing.
- How it will be handled. The weight this page gives you is what someone will have to lift, through whatever door, stairwell or window the job actually has.
Frequently asked questions
How much does glass weigh per square metre?
2.5 kg for every millimetre of thickness. That comes straight from the density of ordinary soda-lime glass, which EN 572-1 puts at 2500 kg/m³ for calculation: a square metre one millimetre thick is 0.001 m³, and 0.001 × 2500 = 2.5 kg. So 4 mm is 10 kg/m², 6 mm is 15 kg/m², and 10 mm is 25 kg/m².
How much does glass weigh per square foot?
About 0.512 lb for every millimetre of thickness, or 13 lb per square foot per inch. In the sizes people actually order: 1/4 inch (6.35 mm) is 3.25 lb/ft², 3/8 inch is 4.88 lb/ft², and 1/2 inch is 6.5 lb/ft². These follow from the same 2500 kg/m³ density, converted exactly.
How do I calculate the weight of a pane of glass?
Multiply length by width by thickness to get the volume, then multiply by the density. Working in metres throughout: a 1200 × 800 mm pane of 6 mm glass is 1.2 × 0.8 × 0.006 = 0.00576 m³, and at 2500 kg/m³ that is 14.4 kg. The shortcut is easier: 0.96 m² × 15 kg/m² = 14.4 kg.
Is toughened glass heavier than ordinary glass?
No. Toughening is a heat treatment that changes the stress in the glass, not its composition or its density, so a toughened pane weighs exactly what an annealed pane of the same size and thickness weighs. The same is true of heat-strengthened glass and of most coatings, whose thickness is measured in nanometres.
How do I work out the weight of laminated glass?
Add the layers, and do not treat the interlayer as glass. A 6.4 mm laminate is usually two 3 mm panes with a 0.38 mm PVB interlayer, or two 4 mm panes with 0.76 mm in the 8.76 mm build. PVB is about 1070 kg/m³ against glass at 2500, so calling the whole stack glass overstates it. Over a square metre, an 8.76 mm laminate is 20.81 kg rather than the 21.9 kg the total thickness would suggest.
What about a double-glazed or insulated unit?
Only the glass weighs anything worth counting. A unit made of two 4 mm panes with a 16 mm cavity is 24 mm thick overall and weighs the same as 8 mm of glass — 20 kg per square metre. The spacer bar and the sealant add a little around the perimeter; the gas fill is negligible. Use the layer builder and mark the cavity as a cavity.
Does the density of glass vary?
A little, and the standard is deliberate about it. EN 572-1 gives 2500 kg/m³ as the value to use for calculation for soda-lime silicate glass, which covers ordinary float glass. Borosilicate is lighter at around 2230 kg/m³, and lead crystal is considerably heavier. The density is an editable field here for exactly that reason.
How thick is 1/4 inch glass in millimetres?
6.35 mm exactly, because an inch is 25.4 mm by definition. That is why nominal 6 mm and nominal 1/4 inch glass are close but not identical: 6 mm is 15 kg/m² and 6.35 mm is 15.875 kg/m², a difference of about 6%. On a large pane that is worth a kilogram or two.
How heavy is a glass shelf?
Enter its size and thickness and the calculator will tell you exactly. As a feel for the numbers, a 900 × 300 mm shelf in 10 mm glass is 0.27 m² × 25 kg/m² = 6.75 kg — before anything is put on it. Whether the brackets and the wall can carry that plus its load is a question for the bracket manufacturer, not for a weight calculator.
How many people does it take to lift a pane?
This calculator will not tell you, and no calculator should. Handling limits depend on the shape and grip as much as the mass — a large thin pane is awkward and fragile in ways a compact heavy object is not — and on local health and safety guidance, which differs by country and by workplace. The weight is the input to that decision, not the decision.
Are my measurements sent anywhere?
No. Every calculation runs in JavaScript in your own browser. Nothing you type is transmitted or stored.