Glazing FAQ
Answers to the most common questions about glass calculations, types, installation, and pricing.
Calculations
How do I calculate glass weight?
Multiply the panel area (m²) by the weight per m² for your glass type and thickness. Glass density is 2,500 kg/m³, which equals 2.5 kg per m² per mm of thickness. A 6mm panel weighs 15 kg/m²; a 10mm panel weighs 25 kg/m². The Glazing Calculator does all of this automatically — enter dimensions and select your glass type for an instant result.
How do I calculate the area of an arch or circle window?
For a full semicircular arch, area = (π/2) × r², where r is half the rebate width. For a circle, area = π × r². The Glazing Calculator handles arches, circles, and triangles automatically — select the shape from the panel dropdown and enter the relevant dimensions.
What glass density does the calculator use?
2,500 kg/m³ — the industry-standard value used in AS 1288 and by glass manufacturers worldwide. This applies to float, toughened, and laminated glass.
How is laminated glass weight calculated?
Laminated glass weight is the sum of both glass panes plus the PVB interlayer. A 6.38mm laminate (3mm glass / 0.38mm PVB / 3mm glass) weighs approximately 15.2 kg/m². The Glazing Calculator includes the interlayer weight automatically when you select a laminated configuration.
How is double glazed unit (IGU) weight calculated?
An IGU's weight is the combined weight of both glass panes. The air or gas fill, aluminium spacer, and edge seal contribute negligible weight. A standard 6/12/6 IGU weighs approximately 30 kg/m².
Can I calculate glass in imperial units (inches)?
Yes. Toggle any panel to inches using the unit selector next to the dimension inputs. Results are displayed in m² and kg.
Glass Types
What is the difference between toughened and laminated glass?
Toughened (tempered) glass is heat-treated to be approximately four times stronger than annealed glass. When broken, it shatters into small, blunt fragments. Laminated glass consists of two or more panes bonded with a PVB interlayer — when broken, fragments remain attached to the interlayer. Both meet AS 1288 Grade A safety glass requirements.
What thickness toughened glass do I need for a balustrade?
AS 1288 and the NCC require Grade A safety glass for all balustrades. For frameless glass balustrades fixed at the base (no top rail), 12mm toughened monolithic glass or 13.52mm laminated glass is the standard minimum for most residential applications. Always verify against AS 1288.
What is Low-E glass and when should I use it?
Low-E (low emissivity) glass has a microscopically thin metallic coating that reflects infrared heat while allowing visible light through. Use Low-E in any double glazed application where thermal performance matters: south and west-facing windows, new residential builds, and commercial projects targeting energy ratings.
What is an IGU?
IGU stands for Insulated Glass Unit — the technical name for a double glazed unit. An IGU consists of two glass panes separated by a sealed spacer, with the cavity filled with air or an inert gas (usually argon). The configuration is expressed as glass/spacer/glass in millimetres — e.g. 6/12/6.
What is annealed glass?
Annealed glass is standard float glass that has been slowly cooled during manufacturing to relieve internal stress. It is the base product from which toughened and laminated glass are made. Annealed glass breaks into large, sharp shards — it does not meet AS 1288 safety glass requirements for human impact zones and should not be used in doors, sidelights, or low-level glazing.
When is safety glass required by law in Australia?
AS 1288 mandates Grade A safety glass in: all doors and sidelights; any glazing with its lower edge below 1,000mm from the finished floor level; glazing within 300mm of a door; shower screens and bathroom enclosures; glass balustrades and pool fencing; and all overhead glazing.
Installation
What clearance do I deduct when ordering replacement glass?
Standard practice is to deduct 3mm from both the width and height of the rebate measurement (1.5mm clearance per side). For double glazed units (IGUs), increase the deduction to 5mm per dimension. Always measure the rebate opening, not the visible glass area.
How many people do I need to lift a glass panel?
Safe Work Australia manual handling guidelines recommend: one person for panels under 25 kg; two people for 25–55 kg; a mechanical lifter for anything over 55 kg. Use the Glazing Calculator to check any panel's weight before it arrives on site.
How do I measure an arch window?
For a semi-circular arch, measure the width of the opening at its widest point (the diameter) and the height from the sill to the top of the arch. If the arch is a full semicircle, the height of the curved portion equals half the width. For ordering, glaziers typically supply a rectangular piece that the arch is cut from — calculate the area of the bounding rectangle and add 10–15% waste. Use the Glazing Calculator's arch shape option to get an accurate area for the curved glass itself.
What glass thickness do I need for a large window?
Minimum thickness depends on panel size, wind load zone, and frame type. AS 1288 Table 4 is the definitive reference. As a general guide for Wind Region A: up to 1m²: 4–5mm minimum; 1–2m²: 6mm minimum; 2–3.5m²: 8mm minimum; 3.5–5.5m²: 10mm minimum; above 5.5m²: 12mm or engineer-specified.
Can I glaze a window myself without a licence?
In Australia, regulations vary by state. In most states, minor repairs — such as replacing a broken pane in a standard residential window — can be done by a homeowner. However, any work involving safety glass locations (as defined by AS 1288), structural glazing, or glass in new buildings generally requires a licensed glazier. In Victoria and Queensland, all glazing work must be carried out by a licensed tradesperson. Always check your state's licensing requirements before proceeding.
Pricing
How much does toughened glass cost per m²?
Prices vary by location, supplier, and order size. As a rough guide in Australia (2025): 6mm toughened clear glass typically costs $60–$120/m² supply-only. Double glazed units (6/12/6) start at approximately $150–$250/m². Always get quotes from your local supplier as prices fluctuate.
Is double glazing worth the extra cost?
For permanent residential installations, almost always yes. A standard 6/12/6 IGU halves heat loss compared to single 6mm glass. The payback period on the additional cost is usually 5–10 years in Australian climates, depending on energy prices and window area.
How long does it take to get glass cut and delivered?
Standard float and toughened glass in common sizes is typically available within 1–3 business days from metropolitan suppliers. Custom-size toughened glass takes 3–5 business days. Laminated glass takes 5–10 business days. Always confirm current lead times with your supplier.
What affects the price of laminated glass?
The main cost factors for laminated glass are: the number of plies and total thickness; the interlayer type (standard PVB, acoustic PVB, or SGP for structural applications); any glass coatings (Low-E, tint); and order quantity. Acoustic laminated glass with a thicker interlayer can cost 30–50% more than standard laminate. Prices also vary significantly between suppliers — always get at least two quotes for large orders.