Measure to the nearest eighth of an inch - don't round your measurements.
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 outside mount - Add at least 3" to each side of the window opening for minimum light gap coverage and maximum privacy.
Is an Outside Mount Right For Your Window?
Before taking any measurements, step back from your window and decide if you want to mount the window treatment inside the window recess, or outside on the wall or molding. We usually recommend an inside mount when possible because it provides a cleaner look. However, an outside mount can make a window appear larger or hide an unattractive window. For an inside mount, the window opening must have enough unobstructed depth to allow mounting.
When measuring for an outside mount, be sure to allow for the height of the product's headrail in your measurements.
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.