Achieving a dark, restful sleeping environment often starts with installing the right blackout curtains. But accurately measuring for the perfect custom blackout curtains can be frustrating. Do you mount the rod inside or outside the window frame? How much extra length and width should you allow? Getting these key details right is the difference between light-blocking success and waking up to annoying slivers of light.
Follow this 5-step blackout curtain measuring guide to finally master the customization process. We’ll walk through the key dimensions needed, plus considerations around room darkening goals. With the right techniques, you’ll only have to measure once for a flawlessly dark space.
Step 1: Decide on Inside or Outside Mounting
The very first decision in mapping out your blackout window treatment is choosing where you’ll mount the supporting curtain rod brackets or hardware. You generally have two options:
- Inside mount – Installed directly to the window frame
- Outside mount – Mounted on the wall above the window frame
Consider the depth and construction of your windows when deciding between installation types:
Inside Mount Considerations
An inside window frame mount can only accommodate a rod if there is adequate frame depth. Single-hung, double-hung, and sliding windows typically have enough space. For shallow specialty windows, an external mount may work better.
One downside of the inside mount lies in potential light leakage. The layering curtain panels can still allow slivers of light to sneak in where the curtains meet the side window frames. This fame gap light is a common frustration.
Outside Mount Considerations
A sturdy ceiling or wall mount above the window provides great versatility in blackout curtain installation. You won’t have light gaps at window edges. Lengths and widths are customizable without the constraints of window depth.
One consideration lies in stability – an outside rod needs to be securely installed into wall studs. Drywall anchors alone may not hold the weight. You’ll also need to account for additional hardware length for full light blocking.
Step 2: Measure Window Width
With the drapery hardware placement decided, it’s time to measure across the actual window opening for an accurate “glass to glass” width dimension. Even if opting for an outside mount, this exact window frame width is key.
Allow Extra Width for Optimal Coverage
When ordering blackout curtains, be sure to add extra width beyond your frame measurements for the most gap-free coverage possible. This provides overlap room when drawing curtains closed.
- Add 2-3 inches if mounting curtain rod inside frame
- Add 4-6 inches if mounting curtain rod outside frame
This additional width prevents the common frustration of light seeping in the sides of standard width curtain panels. Wider also allows for smoothly layering drapes if using lined treatments.
Step 3: Determine Proper Rod Length
The curtain rod length anchors the entire window treatment installation. Mounting placement and style preferences impact ideal rod measurements:
- Inside Mount Length: Extend rod an additional 3-4 inches past the window frame on both sides. This provides stability and room for curtain stackback.
- Outside Mount Length: Extend rod 2-3 inches wider than the overall frame width. This allows the rod ends to fully clear the frame for seamless coverage.
Factor in Additional Length Needs
Consider if added rod length is useful for your particular window situation:
- For extra side light blocking if neighbors are close
- To stagger and layer multiple curtain panels
- To cover several aligned windows with one shared rod
Accurately measuring and marking stud locations first provides an ideal rod length starting point. With supporting anchors in place, it’s simple to then customize to your exact size needs.
Step 4: Measure From Rod to Floor
For the best room darkening results, blackout curtains truly need to run from ceiling to floor. This includes covering the lower window portion below the sill.
Account for Proper Floor Length
Here are benefits of full-length blackout curtain panels:
- Blocks bottom light gaps for complete room darkening.
- Provides a neatly stacked curtain appearance when opened.
- Allows clearance for raised sills if not covering to floor level.
First measure from the rod installation position down to the floor. This sets the maximum curtain length needed. If stopping above the floor level, measure to the bottom window sill instead.
Step 5: Order Curtains in Correct Dimensions
With all the perfect custom measurements to transform your space, it’s time to order your blackout curtains. Be sure to request blackout-specific lining for the best light blockage. Opaque fabric backing layers help prevent both outdoor and indoor light rays.
Since taking accurate measurements is the hardest part, order the max widths and lengths available. This provides flexibility:
- Allows recutting larger panels if installations change down the road
- Perfect for odd measurement situations like angled windows
- Copes with future window alterations if redecorating over time
Your custom window treatments will keep the bedroom dark and peaceful for a long time. Follow these steps to flawlessly block light, reduce noise, and set the stage for deeper sleep.