How to Measure Windows for Curtains: Step-by-Step Guide

Wrong curtain measurements mean panels that look skimpy, gap at the sides, or drag on the floor. Fifteen minutes with a tape measure now saves a return later.

What you'll need

A metal tape measure (cloth tape can stretch and throw off your numbers), a pencil, and a step stool if your window is tall.

Step 1: Decide the mounting type

• Outside mount — rod is fixed on the wall, above and beyond the window frame. Makes the window look larger and blocks more light at the edges. Most homes use this.
• Inside mount — rod sits inside the window frame itself, for a neat, minimal look.

Step 2: Measure the width

Measure the window frame edge to edge. For an outside mount, the rod should extend 4–6 inches beyond the frame on each side — this lets curtains fully clear the glass when opened, so light isn't blocked even when you want it in.

Step 3: Decide fullness

Fullness is how much extra fabric width goes into the curtain compared to the rod length, so it doesn't hang flat:

• 1.5x — lighter, sheer fabrics
• 2x — the most common recommendation, a balanced drape
• 2.5x — heavier fabrics, a fuller, richer look

Step 4: Measure the drop (length)

Decide where the rod will sit first (usually 4–6 inches above the frame for an outside mount), then measure straight down from the rod to where you want the curtain to end:

• Just above the floor — the safest, most universal choice
• Touching the floor — a clean, tailored look
• Puddling on the floor — an extra 2–3 inches, for a formal, dramatic look

Step 5: Do the math — or skip it

Multiply your rod length by the fullness factor to get the total fabric width, then divide by the number of panels. If you'd rather not do this by hand, our free curtain size calculator does all of this instantly and also suggests the closest standard size to buy.

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