What you'll need

Step 1: Choose your mount type

Inside mount — the rod sits within the window frame. Clean, tailored look.

Outside mount — the rod extends 6-15 inches beyond the frame on each side. Blocks more light, makes the window look larger.

Step 2: Measure your rod width and placement

Measure at three points — top, middle, and bottom — and use the smallest measurement for inside mount, or the largest for outside mount.

Step 3: Choose your header style

Your header style affects both the look and how you calculate fullness in the next step.

Step 4: Calculate fullness

Fullness is how much fabric you order relative to your rod width. Order fabric equal to your rod width and curtains will look flat and thin, like a bedsheet, not a curtain.

• Pleated headers: multiply rod width by 2-2.5x
• Soft top and grommet headers: multiply rod width by 1.6-2x

Step 5: Measure your length

Measure from the rod straight down to your desired endpoint, at three points to account for uneven walls or floors.

Try it yourself

Enter your own measurements to calculate exactly how much fabric you need.

Step 6: Determine your number of panels

Divide your total fabric width (from Step 4, or the calculator above) by the panel width you're ordering, and round up. Example: 120 inches needed ÷ 50-inch panels = 2.4, round up to 3 panels. Each panel: 120 ÷ 3 = 40 inches wide.

Common mistakes to avoid

• Measuring at only one point — always check three points
• Skipping fullness — ordering fabric equal to rod width creates flat, thin-looking curtains
• Mixing up inside vs. outside mount — these give completely different starting numbers
• Forgetting obstructions — check for radiators, baseboards, or furniture in the curtain's path

Before you order — double-check

• Mount type decided
• Rod width measured at three points
• Header style selected
• Fullness calculated
• Length measured (floor or puddle)
• Number of panels determined

Still unsure? Email us at support@fossko.com and we'll walk you through it personally.