Glass Thickness: How to Pick the Right Size for Your Project

When you need a new window, a tabletop, or a splash screen, the first question is usually “how thick should the glass be?” The answer depends on a few simple factors: where the glass will go, how much weight it must hold, and how safe it needs to be.

In this guide we walk through the most common glass thicknesses, explain when to use each, and give you practical tips to avoid breakage and waste. Grab a notebook – you’ll want to jot down a few measurements.

Common Thickness Ranges

Most residential glass comes in standard thicknesses measured in millimeters (mm). The typical sizes are:

• 3 mm – Very light, used for picture frames or small decorative panels.
• 4 mm – A step up, good for interior picture frames and tiny shelves.
• 5 mm – Works for most interior windows and simple tabletop inserts.
• 6 mm – Frequently used for bathroom shower doors and larger interior windows.
• 8 mm – Ideal for front doors, large windows, and low‑impact areas.
• 10‑12 mm – Required for heavy loads, big skylights, or safety glass in commercial spaces.

If you’re not sure which size fits, think about two things: the size of the panel and the expected force on it. Bigger panels need thicker glass to stop wobbling, and anything that might get hit (like a door) needs extra strength.

Safety and Regulations

Safety glass comes in two flavors: tempered and laminated. Tempered glass is heat‑treated to break into small chunks, while laminated glass has a plastic layer that holds shards together. For areas where people might slam doors, walk close to the glass, or where kids play, choose tempered or laminated glass at the same thickness you’d use for regular glass.

In the UK, building codes often require at least 6 mm tempered glass for balcony railings and 8 mm for large windows that are within 1.5 m of the floor. When in doubt, ask your supplier which thickness meets local regulations.

Don’t forget about edge finishing. Polished edges look nice but can be sharp. If the glass will be handled a lot, ask for a beveled or rounded edge to keep hands safe.

Now that you know the numbers, here’s a quick cheat sheet:

• Small décor pieces – 3‑4 mm.
• Standard interior windows – 5‑6 mm.
• Bathroom or shower glass – 6‑8 mm tempered.
• Front doors, large panes – 8‑10 mm tempered or laminated.
• Heavy‑duty or commercial – 10‑12 mm tempered or laminated.

Measure the opening, add a little clearance for fitting, and then match the thickness to the load. If you’re ordering online, most suppliers let you filter by thickness, so you won’t have to guess.

Finally, budget matters. Thicker glass costs more, not just for material but also for shipping and handling. If you can meet safety standards with a thinner pane, you’ll save money without sacrificing durability.

In short, pick the thickness that matches the size, the stress it will face, and any safety rules. When you follow these basics, you’ll end up with glass that looks good, stays safe, and doesn’t break the bank.