How to measure an antique dining table for a custom glass top

A glass top is one of the simplest ways to protect an heirloom dining table while letting the timber beneath it breathe. The catch is that the measurements have to be exact, because a panel even a few millimetres too tight can press against the wood on humid Sydney afternoons, while one too loose can slide around and leave ring-shaped wear. Whether you are shielding a 19th-century mahogany extension table in a Brisbane Queenslander or covering a Huon pine refectory table in a Perth bungalow, accurate measuring is the foundation of the whole project.

Most Australian owners inherit tables from grandparents or pick them up at regional auctions in places like Braidwood, Castlemaine, or the Adelaide Hills. Those pieces often arrive with leaves stored in the back of a shed, slight warping from years of dry inland winters, and joinery that was never designed with a glass overlay in mind. That is why the measuring process needs to be slower and more considered than the quick tape job you might do for a modern table.

Glass suppliers and glaziers in Melbourne, Sydney, and Hobart all work in millimetres, while the markings on many antique tables are in inches or in old imperial measurements left by European cabinetmakers. Converting between the two systems is part of the work, and it is also where most mistakes happen. A glass top cut to the wrong size is expensive to replace and impossible to resize, so taking your time now will save money later.

Beyond simple length and width, you also have to think about overhang, edge profiles, skirt depth, and how the table behaves when the leaves are in or out. The steps below walk through each of those in order, drawing on the kind of detailed advice AMG Vintage House has shared on its dining room fit guide for shoppers trying to match table dimensions to a specific space.

Tools and a calm workspace before you start

Set up the table in the spot where you actually plan to use it. A table measured in a Mildura garage in midsummer can measure a few millimetres longer in July once the timber swells in coastal humidity. If you live in a Queenslander in Brisbane or a Victorian terrace in Fitzroy, the same principle applies: climate matters, and the table should be measured in the room it lives in. Leave it there for at least a week before you start so the wood reaches a stable size.

The tools you need are simple. A rigid steel ruler or a quality tape measure marked in millimetres, a soft pencil, a roll of masking tape, a notepad, and a helper. A laser measure is handy for long tables, but it can give misleading readings on glossy polished surfaces, so always cross-check with a physical tape. A small spirit level confirms that the table is sitting flat before you trust any number you write down.

Clear the table of cloths, runners, and centrepieces. If it has extension leaves, slot them in and check that the slides are properly seated, since partially engaged leaves will throw off your readings by a surprising amount. Take a moment to photograph the table from above once it is cleared. Those images are useful if you need to talk to a glazier in Canberra or order a replacement panel years later.

Measuring the tabletop surface itself

Begin with the overall length, measuring from the two furthest points along the longest edge. Run the tape along the centre line of the table, not the outer skirt, because skirts often flare slightly outward on period pieces. If the table has a shaped or serpentine front, measure at the widest point as well as the narrowest. Both numbers matter, since a custom glass top has to clear the widest curve without resting on it.

Width is measured the same way, across the centre from one long edge to the other. On round or oval tables you need a single diameter figure, but for oval shapes record both the long and short axis. Square tables are the easiest, yet check each side individually. Many antique tables, even those that look perfectly square, vary by a couple of millimetres from side to side. Use the larger of the two numbers as your working measurement.

Height is worth recording too, even though the glass top sits flat on the surface. The overall height tells your glazier how thick the glass can be without making the table feel bulky, and helps you choose between 4 mm, 6 mm, or 10 mm toughened glass. A heavy cedar or blackwood table carries a thicker panel with ease, while a delicate Victorian walnut side table looks better with a thinner overlay.

Always write your measurements down in millimetres, with the number written twice and read aloud to your helper. Australian glaziers and suppliers, including those referenced in AMG Vintage House's notes on what size dining room set will fit, work to the millimetre, and a digit transposed between 1780 mm and 1870 mm is an expensive mistake. Photograph each measurement with a ruler laid next to the tape so the figures can be checked later.

Leaves, extensions, and non-rectangular shapes

If your table has one or more extension leaves, you need two sets of measurements. The closed position is the one most people use day-to-day, but if you regularly host long lunch tables or Christmas gatherings, the open length is just as important. Many Australian households still pull out a six or eight-seater for Easter and Boxing Day, and a glass top that only fits the closed position will not protect the table when it matters most.

Measure each leaf individually and compare its length to the main table body. They should be identical, but on older pieces they sometimes differ by a millimetre or two. Use the smaller of the two figures as your working measurement when ordering a single glass top, or order two separate panels if you want full coverage in both configurations. Two thinner panels can be safer than one very long sheet, since long panels are harder to transport across regional areas like the Top End or the Pilbara.

Round tables with central pedestals need a circular or near-circular cut. Measure the diameter in three places, because antique round tables are rarely perfectly circular, and a tight glass top can crack if the curvature is uneven. For octagonal, hexagonal, or shaped tables, sketch the outline on butcher's paper and label each edge. Your glazier can transfer that template directly to the cutting floor.

Edge clearance, overhang, and skirt depth

Once you have the raw dimensions, subtract a small clearance margin so the glass does not press against the wood. A safe allowance is 3 mm per side for most tables, and 5 mm for solid timber pieces that are likely to swell in humid coastal climates around Cairns, Darwin, or the NSW North Coast. This clearance also creates a tiny breathing gap that prevents condensation being trapped between the glass and the polish.

The overhang of the table edge matters because the glass should not extend past it. If your table has a lip, moulded edge, or shaped skirt, the glass top needs to stop just inside that profile. Mark the perimeter with small pieces of masking tape before you measure, so you can see the finished line clearly. This is particularly important for pieces with breadboard ends, where the end panels slide in and out of their housings and the glass must clear the joinery.

Skirt depth affects how far the glass can drop below the top edge of the apron. A shallow skirt may require a thinner glass to avoid visual heaviness, while a deep skirt can carry a chunkier panel without looking out of place. If you use felt bumpers or small clear discs at each corner of the top, factor in their height as well, so the glass sits level and does not rock on uneven timber.

Working with a glazier and ordering the panel

Most Australian glaziers can supply toughened or laminated glass in standard thicknesses, with polished edges as standard. Toughened glass is the safer choice for a dining table, especially in family homes, and it complies with Australian Standard AS/NZS 2208 for safety glazing. Laminated glass offers an extra layer of security for particularly valuable antiques, although it is heavier and slightly more expensive.

Send your glazier a clear sketch, the photographs you took earlier, and your written measurements in millimetres. Ask them to confirm the numbers back to you in writing before cutting begins. Many glaziers in Sydney and Melbourne will also come to your home to template the table, which is the safest option if the piece is unusually shaped or has warped over the decades. A small template fee is well worth it for an heirloom.

Check whether your table is protected under any state heritage legislation before you start. In New South Wales, the Heritage Act 1977 lists items of state significance, and in Victoria, the Heritage Register under the Heritage Act 2017 works similarly. Most family dining tables are not listed, but if yours is part of a heritage home in Adelaide or a registered homestead in Tasmania, any modification, including adding a glass overlay, may need approval or at least a chat with a heritage adviser.

Practical recommendations for a smooth measuring process

When the panel arrives, lay a soft towel on the table, lower the glass onto it, and check the fit before removing the protective film. If anything looks off, contact your glazier straight away rather than trying to live with a piece that does not sit right. A correctly measured glass top will protect your antique dining table for decades, letting the timber age gracefully while every meal sits safely on a clear, polished surface. Browse the rest of AMG Vintage House's collection and fitting advice to find the right match for your home.