How to Measure for Custom Curtains | Get the Fit Right

For the full breakdown, see our best Custom Curtains guide.

Getting custom curtains to hang perfectly starts with two numbers: the width and the drop. Measure the hardware you already have, not the window glass, and you eliminate most fitting headaches before you order. The process takes about ten minutes with a steel tape measure and a step stool.

Measure The Width: Track Or Pole First

If your curtain track or pole is already installed, measure its full width end to end. For poles, exclude the decorative finials at each tip — those add length that won’t hold fabric.

No hardware up yet? Measure the window opening, then add coverage on each side so the curtains can stack back when open and still cover the glass. Plan for roughly 4–10 inches of extra width per side; the exact number depends on your style preference. Mounting the rod or track above the frame — about 3–6 inches up, extending 6–10 inches past each side — adds light and makes windows look taller. Dunelm’s buying guide suggests positioning the track about 15 cm above the recess and extending it 15–20 cm past each side, which lands in the same range.

The width you record should be the full span of the pole or track, not the window. That single choice prevents most sizing errors.

Fullness: How Much Fabric Width You Need

Curtains need extra fabric width to gather properly. The right multiplier depends on your heading style:

• Eyelet curtains: 2x the track or pole width for a full gathered look.
• Tab top curtains: 1.5x the track or pole width.
• Pencil pleat curtains: roughly 1x the track width — the pleats create the fullness.

Manufacturer instructions vary, and some drapery styles specify a 200% fullness multiplier. When in doubt, check the product’s own fitting guide before ordering. JCPenney’s curtain guide notes that fuller styles need more fabric, so match the multiplier to the look you want rather than defaulting to one number.

Measure The Drop: Mounting Point To Desired Length

The drop runs from the top of the track or pole — where the curtain attaches — down to where you want the hem to land. Decide the endpoint first: sill length, below the sill, floor length, or puddle length for a dramatic drape.

For floor-length curtains, keep the hem about 1 cm above the floor so fabric doesn’t drag or collect dust. If you’re hanging curtains above a radiator, leave roughly 3 cm of clearance at the bottom so heat can circulate into the room.

Using rings or hooks? Measure from the rod to the floor, then subtract the distance from the rod down to the bottom of the ring or hook. That offset gives you the finished drapery length, not the rod-to-floor distance.

Write the width first, then the drop, and round to the nearest 1/8 inch for a clean fit. Restoration Hardware’s measuring guide follows this same format, and it keeps your order sheet consistent when you’re comparing options.

Common Mistakes And Tools That Help

Use a steel or metal tape measure; fabric tapes stretch and give you a false reading. Measure twice, and note the width before the length every time.

The most frequent errors are easy to avoid:

• Measuring the window glass instead of the track or pole width.
• Forgetting to exclude finials from the pole measurement.
• Skipping the stack-back allowance when no hardware is installed yet.
• Mixing up width and height when you write down your numbers.

Compatibility matters too. Inside-mount or custom-fit setups depend on your hardware type — pole, track, rings, eyelets, tab tops, or pencil pleats each change where you measure from. If your window lacks enough depth for an inside mount, plan for an outside mount instead. When you’re ready to compare options that fit your measurements, our roundup of the best custom curtains breaks down the top choices by style and price.