Find your curtain size.
Count the packages.
Plan a straight rod, choose your fullness, and check a curtain package before you buy. Keep the measurements in a printable shopping list.
Measure. Match. Hang.
One window, one layer, straight rods or tracks. This checks dimensions and quantities; it does not certify mounting hardware, light blocking, or how much glass stays clear when open.
What width curtains do I need?
Measure the outside trim width and add your chosen rod extension on both sides. Multiply this rod span by the fullness you want. Divide by the flat width of one panel, rounding up. A split opening uses an equal whole number of panels on each side. Package counts round up separately; extra panels can be kept as spares.
Example: a 48-inch window with 6 inches of rod extension on each side has a 60-inch span. At 2× fullness, the fabric target is 120 inches. With 50-inch panels and an equal split, use four panels—two packages of two. Three panels have enough total width, but cannot divide equally.
How long should the panels be?
Target length = floor-to-trim-top + rod height above trim + fabric-top adjustment − floor gap. A negative floor gap adds length for puddling. A negative heading adjustment accounts for fabric hanging below the reference point. The checker reports how much a panel falls short or exceeds your exact target, and its resulting floor gap. Adding panels fixes width, never length.
A longer panel may be hemmed if its construction allows it; the difference shown is the finished length to remove, not a cutting allowance. Check care instructions and shrinkage before hemming. Ready-made length labels and heading conventions vary: confirm where the seller measures from.
Choose the look, then verify the hardware
The 1.5×, 2× and 2.5× choices are starting points for flat fabric. Follow the curtain maker’s guidance for your heading and fabric. Pre-pleated products may already include fullness in their finished coverage widths; do not multiply it again. Side returns, overlaps, stack-back space and rod end curves need additional planning. Rod extension and height are adjustable examples, not installation requirements.
The diagram shows your planned coverage when closed. It is a measurement sketch, not a preview of fabric drape. Check brackets, center supports, anchors, rod diameter and load ratings against the actual hardware and wall. Ring, hook and clip counts depend on the chosen product, so the shopping list leaves these for confirmation.
Sources & scope
- IKEA MATILDA product guidance: fullness calculation, per-curtain width, pair packaging and washing before hemming.
- IKEA curtain measurement guide: rod span, length and panel-count planning.
Sources checked October 19, 2026. General calculation tool; no product fit testing, prices or affiliate links. Your entries stay in page memory and are not saved by this planner. Print to keep a copy. See our Privacy Policy.