A glass thickness gauge is a handheld meter that measures the thickness of each glass pane, the air space between them, and the overall thickness of an insulated glass unit. It reads from one side of the window, so you can test installed windows and order the correct replacement IG unit without guesswork.

What does a glass thickness gauge measure?

An insulated glass (IG) unit is built from two or three panes of glass separated by sealed air spaces. A glass thickness gauge reports the following in one reading:

•       Glass thickness of each pane

•       Air space between the panes

•       Overall IG thickness of the full unit

Models like the EDTM Glass-Chek PRO (GC3001) measure single, double, and triple-pane windows at the push of a button.

How does a glass thickness gauge work?

The gauge is placed against the window and takes its measurement from one side of the glass. The GC3001 uses a high-precision laser for its readings, and results appear on screen as soon as you press the button. EDTM recommends measuring at the bottom center of the window, which gives the most accurate and repeatable results.

You can also choose how results are displayed, including fractions, thousandths of an inch, or decimal millimeters. For a full walkthrough of the process, see our guide on how to use a glass thickness gauge on insulated glass.

Why does glass thickness matter when replacing a window?

If a replacement IG unit has the wrong glass thickness or air space, it may not fit the existing frame. Measuring by hand is difficult because the edges of the unit are usually hidden inside the frame. A gauge gives you the exact numbers from the surface of the window, so you can order the right unit the first time and avoid costly reorders.

What else can a glass thickness meter detect?

Many gauges do more than measure thickness. A glass thickness meter such as the Glass-Chek PRO can also:

•       Detect Low-E coatings and show whether the coating is hard coat or soft coat

•       Classify soft coat Low-E as single, double, or triple silver

•       Locate the Low-E surface from one side of a double-pane window, which helps when you only have access to the inside

•       Show total thickness of laminated glass

•       Work on tinted glass and suspended film such as Heat Mirror

Knowing the Low-E type matters. The wrong coating can reduce a window's energy performance, and it can make the new unit look different from the other windows in the building.

The GC3200 Glass-Chek ELITE adds laminated glass identification, laminate layer thickness, and a graphical display that draws the window approximately to scale.

Who uses a glass thickness measuring tool?

A glass thickness measuring tool is useful for anyone who needs to know exactly what is in a window:

•       Window installers and glaziers ordering replacement IG units

•       Production personnel spot-checking glass in manufacturing

•       Building inspectors and surveyors checking existing windows

•       Technicians checking Low-E coating orientation during installation or inspection

Which EDTM glass thickness gauge should you choose?

EDTM offers two models: the GC3001 Glass-Chek PRO for core measurement and Low-E detection, and the GC3200 Glass-Chek ELITE, which adds laminated glass detection and a graphical display. For a side-by-side look, read our GC3200 vs. GC3001 comparison.

Frequently asked questions

Can you measure glass thickness without removing the window?

Yes. A glass thickness gauge is designed to test windows already installed in the field. For details, see our guide to measuring glass thickness in an installed window.

How thick a window can a glass thickness gauge measure?

The GC3001 Glass-Chek PRO has a measurement range of approximately 2 inches, up from 1.2 inches on earlier models.

Can a glass thickness gauge measure triple-pane windows?

Yes. The Glass-Chek PRO and Glass-Chek ELITE measure glass, air space, and overall IG thickness of triple-pane windows with a single button push.

Can a glass thickness gauge measure laminated glass?

Yes. The GC3001 displays the total thickness of laminated glass. The GC3200 Glass-Chek ELITE can also identify laminated glass and measure the thickness of the laminate inner layer.

What units can a glass thickness gauge display?

The GC3001 can show actual values or values rounded to ASTM standards in fractions of an inch, thousandths of an inch, decimal millimeters, and more.

What powers a glass thickness gauge?

The GC3001 runs on a common, replaceable 9-volt alkaline battery and includes a protective carrying case.

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