How to Measure Glass for A Cat Flap.

Cheap Cat Flap Installation in London - Cat out of glass

Cat Out of Glass


As cat flap fitters we regularly install cat flap into double glazing. We are often asked how much does it cost to put a cat flap in double glazing. As the glass is charged per square meter is often almost impossible to cost without an accurate measurement of the glass.

Take a look at the photo to the right; You will need to measure the width first from A to B and height from C to D.

When ordering glass, a qualified cat flap fitter will always measure and write down the width first.

This is the industry standard for all glass manufacturers; it enables them to identify width from height every time by looking at a measurement. The measurement must be in either millimeters or centimeters as glass cutters standard is metric and not imperial.

When measuring a window width or height, always measure from inside of the window frame where the bead of the frame & glass meet.

So how do you measure a double glazed unit for a cat flap?

Hopefully, you can use this blog to assist you; it can be helpful for glass in UPVC, wood and aluminium frames.

There is an advantage in being able to measure accurately; it will enable you to get a quicker quote and also the cat flap fitted sooner. No more sleepless nights caused by constant meowing and scratching at the door.

When measuring the double glazed replacement pane for the cat flap you need to be facing the window from the inside of your home, also a lot easier if it’s raining cats and dogs!! Sorry had to get that in.


When measuring height, it is always easier to read the measuring tape from the top in toy line of sight.

How to Measure Glass for A Cat Flap. 1

Measuring Height can be tricky, and it is always advisable to have someone hold the bottom of the measuring tape in place. Always ensure if someone is holding the bottom that they are holding it in the correct position where the bead meets the frame.

After measuring the glass, to get an accurate quote always give the cat flap fitter at least two photos. Inside of the window showing the spacer bar and the whole window in one shot are very useful for them to judge the cost of putting a cat flap in a double glazed unit.

Specifying your spacer bar colour can also speed up the process, the spacer bar is located inside your two panes of glass.

The spacer bar in this photo is silver which is the most common bar colour in double glazed units. Your options could be Silver, Black, White & Brown.

To recap always measured the width & height of the glass from the inside of the frame; write down your measurement width first then height. Always check, check and check again. And take photographs by doing this a cat flap fitter should easily be able to cost the job instantly.

Once a correct measurement as been verified by the cat flap fitter, you are looking at five working days for the glass manufacturer to cut the glass. Then the cat flap installation should be speedy and trouble-free.

Visit our cat training page for more in-depth advice on training a cat to use a cat flap; we are cat lovers and experts in installation of cat flap into glass and double glazing feel free to write any comments.

About the Author:

Cat Out of Glass

Cat out of Glass are specialists in pet doors, dog doors, and cat flap fitting. Serving the South of England and beyond, we’re experts installers for glass and double glazing.

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