Blackout curtains are one of those purchases that either work perfectly or annoy you every single morning. The difference almost never comes down to the fabric. It comes down to measuring correctly before you order. Here is how to get it right the first time.
Step 1: Measure the width, then double it
Measure the width of your window, including the frame. For curtains to actually block light and hang with full, soft folds, you want total curtain width to be 1.5 to 2 times the window width. A 60 inch window needs roughly 120 inches of total panel width, which usually means two panels of 52 to 60 inches each. Curtains stretched flat across a window look thin and leak light at every fold.
Step 2: Pick your length by where you want them to end
There are three standard looks. Sill length ends just below the window sill and suits kitchens and small windows. Floor length ends about half an inch above the floor and is the safest choice for bedrooms and living rooms; 84 inch panels fit most standard 8 foot ceilings when the rod is mounted a few inches above the frame. Puddle length runs 1 to 3 inches longer than the floor for a more formal, romantic look, but it collects dust and pet hair, so skip it in high traffic rooms.
If you are between sizes, go longer. A curtain that ends awkwardly mid-wall shortens the whole room. Mounting the rod 4 to 6 inches above the window frame, or even close to the ceiling, makes windows look taller and improves light blocking at the top edge.
Step 3: Decide how dark you actually want the room
True blackout fabric uses a woven or coated layer that blocks 95 to 100 percent of light, which is what you want for bedrooms, nurseries, and shift sleepers. Room darkening fabric blocks most light but lets a soft glow through, which many people prefer for living spaces. If you sleep next to a streetlight, choose true blackout and hang the panels wider than the window so light cannot sneak around the sides.
Step 4: Think about temperature, not just light
The same dense weave that blocks light also insulates. Blackout curtains measurably reduce heat coming through windows in summer and slow heat loss in winter, which matters most for bedrooms with big windows. Thermal insulated panels are worth it if your room runs hot in the afternoon.
Quick checklist before you order
Total panel width at least 1.5 times the window width. Length chosen for half an inch above the floor unless you want a puddle. Rod mounted 4 to 6 inches above the frame and extending 6 to 10 inches past each side. Grommet tops slide more smoothly and hang in even folds; rod pockets look softer but move less freely.
Our thermal blackout curtains come in 63 and 84 inch lengths in multiple colors, and for covered patios our waterproof outdoor curtain handles sun and weather. Both ship free across the US with 30 day returns, so you can check the fit in your own room.