Use a steel measuring tape and measure down to the nearest 1/8".
On your notes, clearly indicate which measurement is the width and which is the height. It is very common to transpose measurements. Always indicate the WIDTH measurement first, then the HEIGHT last. (W x H)
Remember one very important thing when measuring for an inside mount - Take the ACTUAL WINDOW OPENING SIZE to give to us, our factory will take all the proper allowances for it to fit into that opening.
Be Confident: Inside or Outside Mount-Which To Choose?
Decide which you want BEFORE you take any measurements.
We usually recommend an inside mount because it provides a cleaner look.
However, an outside mount can make a window look larger or hide an unattractive window.
If you want an inside mount, make sure the window opening has enough unobstructed depth to allow for mounting.
If you want an outside mount, be sure to allow for the height of the product's headrail in your measurement.
Always remember: we will custom make your blinds to the sizes you write on the order. If these sizes are incorrect it is impossible to change the blind, so take your time and double check your measurements.
Measure the width top, center and bottom, recording the narrowest width. Measure the height left, right and center recording the shortest height. When you specify inside mount, we will make your blind slightly smaller than specified to allow for operating clearance. We will deduct between 1/16" to 3/8" from the width on each side, and 1/4" to 1/2" from the height. For a flush inside mount (the blind completely recessed so the top of the blind does not project out of the opening) check that you have enough depth.