How to Measure for Curtains in 5 Steps

Measuring for curtains takes about ten minutes and a steel tape measure: a cloth tape stretches, and windows are often wider than they look. Write each number down as you go, and measure every window, even ones that look the same. The curtain size calculator can do all the math below once you have the measurements.

Step 1: Choose inside or outside mount

• Outside mount (most common): the rod goes on the wall above the window and extends past each side. The curtains can open fully off the glass, and the window looks bigger.
• Inside mount: the rod fits inside the window frame. It’s neat for deep frames, café curtains and kitchens, but open curtains always cover some of the glass.

Step 2: Measure the window

1. Width: measure from the outside edge of the trim on one side to the outside edge on the other. For an inside mount, measure inside the frame, at the top, middle and bottom, and use the smallest number.
2. Height: measure from the top of the trim to the sill.
3. Below the window: measure from the sill to the floor.
4. Above the window: measure from the top of the trim to the ceiling (or to the crown molding).

Step 3: Decide where the rod goes

• Height: at least 4–6 inches above the frame. For a taller look, hang it about two-thirds of the way from the top of the window to the ceiling, or just below crown molding. See how high to hang curtains for examples.
• Width: extend the rod 6–12 inches past each side of the window, so open curtains stack on the wall instead of over the glass. The rod length is the window width plus both extensions: a 48-inch window with 10 inches each side needs a 68-inch rod. The curtain rod length calculator shows which adjustable rod to buy.

Step 4: Work out the curtain width

Curtains need extra fabric, called fullness, so they fall in soft folds when closed. Multiply the rod length by:

Look	Fullness	For a 68 in rod
Flat, modern	1.5×	102 in
Standard (grommet, back tab, rings)	2×	136 in
Full (pinch pleat, rod pocket)	2.5×	170 in
Sheers	3×	204 in

Then divide by the width of one panel to find how many panels you need. Ready-made panels are usually 50 to 54 inches wide, so 136 inches is 3 panels, rounded up to 4 for a pair (2 per side).

Step 5: Measure the length

Measure from the rod down to where you want the curtains to end:

Style	Where the hem ends
Sill	Just above the windowsill
Apron	About 4 in below the sill
Float (floor)	¼–½ in above the floor
Break	1–2 in onto the floor
Puddle	3–6 in onto the floor

Then match the number to a standard length: 63, 84, 95, 96, 108 or 120 inches. If yours falls between two sizes, buy the nearest one and move the rod up or down an inch or two, or have the curtains hemmed. The curtain size chart shows which length suits which room.

Common mistakes

• Measuring only the glass. Include the trim, or the curtains won’t cover the window edges.
• Hanging the rod right on top of the frame. It makes windows and ceilings look lower; go at least 4 inches higher.
• Buying one pair for a wide window. Two 50-inch panels on a 68-inch rod give only about 1.5× fullness: the curtains look flat and barely meet in the middle.
• Forgetting the finials. Rod lengths don’t include the decorative ends, which add 2–6 inches. Check there’s room near walls and corners.

Free printable measuring worksheet

Take this two-page worksheet with you while you measure: a labeled diagram (A to F), a form for each of four windows and a quick-reference box with the rules above. Download: US Letter PDF · A4 PDF

Doors, bay windows and DIY curtains

• Sliding glass doors and French doors: the rod extends further so the door still works; see the door curtain calculator.
• Bay and bow windows: measure each section separately; the bay window curtain calculator works out the rod, corners and panels.
• Sewing your own: the curtain fabric calculator turns your finished size into yards of fabric.