Glass Cut Size Calculator
Enter your window or door opening dimensions. Get the exact glass cut size accounting for setting pads, thermal expansion, and glass type.
Glass Cut Size Calculator
Glass needs gaps for rubber setting pads and thermal expansion. Enter your opening dimensions and the calculator determines the exact cut size.
Standard window glass — recommended gap: 2mm per side
Recommended Gaps by Glass Type
| Glass Type | Gap Per Side | Notes |
|---|---|---|
| Float Glass (interior) | 2mm | Mirrors, picture frames |
| Float Glass (exterior) | 3mm | Windows, doors |
| Tempered Glass | 3-5mm | Shower doors, balustrades |
| Laminated Glass | 2-3mm | Security, skylights |
| Insulated Glass (IGU) | 4-6mm | Double-glazed windows |
| Fire-rated Glass | 3-5mm | Must follow fire rating specs |
Tips for Accurate Glass Cutting
Always Measure the Opening
Never measure the glass itself. Measure the opening (rebate) where the glass sits. Glass is always cut smaller than the opening.
Use Setting Blocks
Place rubber setting blocks at quarter points along the bottom edge. They support the glass and allow for drainage and expansion.
Account for Thermal Expansion
Glass expands and contracts with temperature. Larger panels need larger gaps. Exterior installations need more gap than interior.
Check Tolerance Specs
Glass cutting tolerance is typically ±1-2mm. For critical applications, specify exact tolerances when ordering.
Frequently Asked Questions
How much smaller should glass be than the opening?
Typically 3-6mm per side (6-12mm total in each dimension). The exact gap depends on glass type, size, and whether it's interior or exterior.
Do I need setting blocks for all glass?
Yes. Setting blocks prevent glass from touching the frame directly, which causes stress cracks. Use neoprene or EPDM blocks at quarter points.
What is the glass cutting tolerance?
Standard tolerance is ±1-2mm. For large panels (>2m), expect ±2-3mm. Always confirm tolerance with your glass supplier.
How do I calculate glass area for pricing?
Multiply cut width × cut height, then divide by 1,000,000 for square meters. Glass is typically priced per square meter.
Cut Multiple Glass Panels?
Use the 2D optimizer to arrange multiple glass cuts on each sheet and minimize waste.
Launch 2D Optimizer