Measure your glass in 5 easy steps

Step 1:Measure the frame

Hold the ruler across the edge of the window frame, from its inside face to its outside face, where the glass sits.

Example: 30 mm

Step 2:Mark the inside gap

On the inside, lay the card flat across the frame. Slide a toothpick under it until it touches the glass, and mark the toothpick at the card's edge.

Step 3:Mark the outside gap

Do the same on the outside of the window with the second toothpick.

Step 4:Measure the marks

Measure each toothpick from its tip to your mark with the ruler.

Example: 4 mm inside, 3 mm outside

Step 5:Do the maths

Frame minus both gaps is your glass thickness, or let the calculator do it for you.

Example: 30 − 4 − 3 = 23 mm