Measuring the panel for a window

How much smaller should the stained glass panel be in order to fit a window? 1/8 of an inch on each side?

Milly’s reply:

Yes, 1/8 of an inch smaller each side is perfect. That allows for the silicon or putty and means that you don’t damage the window trying to get it in.

It’s called the ‘Fitting Size’.

I have a page all about measuring, if you have any more questions you might find the answer here:

Measuring for a Window

Good luck, and I hope it fits. It’s always a bit of a ‘heart in the mouth’ moment…

formula for using 1/2″ U Zinc

Using 1/2″ U zinc:

The bite on each size of the 1/2″ U zinc is 3/16″.
Total bite for both sizes is 3/8″
Zinc is 1/2″ + 1/2″ =1″ – 3/8″ = 5/8″

Reduce the pattern size by 5/8″ overall.
If the pattern is computer drawn and printed, cut down the middle of the printed line and you’ll be fine.
If the pattern is hand drawn, then take the additional 1/8″ and use shims to position the finished window just to be safe.

Milly says: Thanks for taking the time to post, that’s really helpful.


2 thoughts on “Measuring the panel for a window”

    • Good question Venus. For square or rectangular panels I’d recommend starting at the edges with a right-angled jig that’s at least the full height and width of the piece.
      For ovals or circles you can do either but make sure that you have a robust way of holding your pieces in place – nails and board – otherwise there’ll be trouble ahead!


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