A good fit starts before you choose a colour or finish. Windows that look identical can differ slightly in size, and even a small difference can affect how custom blinds sit and operate. You can take preliminary measurements with a metal tape measure, a pencil and a place to record each window separately. 

Step 1: Decide where the blinds will sit.  

An inside mount fits within the window opening and leaves the frame visible. An outside mount attaches above or around the opening, covering more of the frame. Decide which look you prefer before measuring, because the two methods use different starting points. For an inside mount, also measure the depth of the opening and note any handles or hardware that could get in the way.  

Step 2: Measure the width in three places.  

Hold the tape straight across the inside of the opening at the top, middle and bottom. Write down all three measurements, then circle the narrowest. A frame can taper slightly, and measuring only at the top may leave you with blinds that bind lower down. 

Step 3: Measure the height in three places.  

Measure from the top of the opening to the sill on the left, in the centre and on the right. Record each result rather than assuming the sill is level. Measure diagonally from corner to corner as well. If the diagonal measurements differ substantially, ask about an outside mount before ordering. 

Step 4: Record the depth and any obstructions.  

Measure from the front edge of the frame back toward the glass. Note window cranks, locks, handles and anything else that projects into the opening. The depth needed depends on the blind and mounting hardware you choose, so check the product requirements before settling on an inside mount.  

Step 5: Mark the area you want covered. 

 Decide how far beyond the opening you want the blinds to extend on each side and where the headrail will attach above the window. Measure the full width of that planned coverage area, then measure from the planned mounting point down to where you want the blinds to end. Check that there is enough suitable space for the brackets and that nearby doors, trim or furniture will not interfere. 

An outside mount may also be useful when a frame is shallow or noticeably out of square. Because overlap and hardware requirements vary by product, confirm the final dimensions for your chosen blinds rather than applying a universal allowance.  

Step 6: Label every window and measure it again. 

Record the room, window location, mounting choice, width, height and depth together. Mark whether each number is an opening measurement or your desired outside coverage. Never rely on one window’s dimensions for another, even if they appear to match. 

These measurements give you a useful starting point when shopping for blinds in Red Deer. At Auburn & Ash, we can help you choose a treatment that suits your space and confirm the details needed for a proper fit. 

Contact us to tell us about your windows!