Measuring for a curtain rod is one of those tasks that looks simple until your curtains are blocking half the window or bunching against the wall. The good news: once you know the four numbers that matter, you'll get it right every time. Here's exactly how to measure curtain rods — width, height, stackback, and projection — before you buy or order anything.
What You'll Need Before You Start
Grab a steel tape measure (not a fabric sewing tape — it stretches and throws off your numbers), a pencil, and something to write on. Measure each window separately, even if they look identical. Windows in the same room can vary by half an inch or more, and that gap matters.
Tip: If you're measuring multiple windows, label each measurement by room and window position (e.g., "living room left"). You'll thank yourself later.
Step 1: Measure Your Rod Width
This is the most important measurement — and the one most people get wrong. The curtain rod should never be the same width as your window opening. It needs to extend past the window frame on both sides so that when your curtains are open, they stack on the wall, not on the glass.
Getting your curtain rod width right determines how much light enters the room and how the window looks when the curtains are pulled open. Here's how to calculate it:
- Measure the full width of your window frame, from the outer edge of the trim on the left to the outer edge on the right. This is your window frame width.
- Add 6 to 15 inches on each side (12 to 30 inches total). For most rooms, 8 inches per side is a good starting point. For a more dramatic look — or if you want maximum light when the curtains are open — go closer to 15 inches per side.
- That final number is your target curtain rod length. Standard curtain rod width options typically come in adjustable ranges.
Example: Window frame width = 48 inches. Add 8 inches per side = 64 inches total rod length. You'd look for an adjustable rod in the 48–84 inch range.
Why it matters (the stackback rule): When curtains are drawn open, they bunch into a stack on each side. That stack is typically 10–15 inches wide per panel. If your rod doesn't extend far enough, the stack covers part of your window even when the curtains are "open." Extending the rod past the frame keeps the glass completely clear and makes the window — and the room — look larger.
Step 2: Measure Your Rod Height
Where you mount the rod matters as much as how wide it is. Hanging it too close to the window makes ceilings feel lower. The standard guidance: mount the rod 4 to 6 inches above the top of the window frame or close to the ceilling. If you have high ceilings (9 feet or more), going 8 to 12 inches above the frame — or even closer to the ceiling — creates a more dramatic effect and makes the room feel taller.
- Measure from the top of your window frame upward to where you want to place the rod bracket.
- Mark that spot lightly with a pencil on both sides of the window.
- Use a level to confirm the two marks are at the same height before drilling.
Your curtain drop (panel length) is measured from the bottom of the rod — or from the bottom of the curtain ring if you're using rings — down to where you want the hem to fall. Floor-length panels typically end ½ inch above the floor for a clean look, or 1 to 3 inches past the floor for a relaxed puddle effect.
Step 3: Choose the Right Rod Diameter for Your Fabric
Rod diameter affects both look and function. A thin rod under a heavy fabric will bow in the middle over time. A thick rod under a lightweight sheer can look heavy and out of proportion. Match the diameter to your fabric weight, by the way, use same rod diameter in one space:
| Fabric Weight | GSM Range | Recommended Rod Diameter | Example Curtains |
|---|---|---|---|
| Lightweight sheers | 100–180 GSM | ⅝ inch (16mm) | Ella, Lilith, Tom sheer |
| Mid-weight linen / cotton | 280–360 GSM | ¾–1 inch (19–25mm) | Lesley (339 GSM), Harris (450 GSM) |
| Heavyweight velvet / chenille | 390–540 GSM | 1–1¼ inch (25–32mm) | Elma velvet (420 GSM), Penelope (536 GSM) |
| Blackout / thermal | 270–360 GSM | 1 inch (25mm) | Gary blackout (270 GSM) |
If you're unsure of your fabric's weight, order free swatches before buying your rod — you'll be able to feel the weight and drape in person before committing to either.
Step 4: Check Your Projection Clearance
Projection is how far the rod bracket extends from the wall. It's the measurement people forget until they realize their curtains are dragging against the window trim.
The minimum clearance you need depends on your heading style:
- Grommet curtains: need the most projection — at least 3 to 4 inches — so the rings can fold back without catching on trim or handles.
- Rod pocket, tab top, or back tab: 2.5 to 3 inches is usually enough.
- Pinch pleat with rings: 3 inches minimum to allow smooth glide.
Also check for any protruding window hardware — handles, locks, or cranks. Your bracket projection must clear them completely.
Quick Reference: Curtain Rod Measurement Cheat Sheet
| Measurement | Formula | Notes |
|---|---|---|
| Rod width | Frame width + 8–12" per side | More overhang = more light, bigger feel |
| Rod height | 4–6" above frame (up to 12" for high ceilings) | Higher = taller-looking room |
| Curtain drop | Bottom of rod to floor (minus ½") | Measure after rod is placed |
| Rod diameter | Match to fabric GSM (see table above) | Heavy fabric needs a thicker rod |
| Projection | Minimum 2.5–4" from wall | Depends on heading style and window hardware |
Why Getting the Measurement Right Matters Even More with Custom Curtains
With ready-made curtains, a slightly off measurement might just mean a bit more bunching or a small gap at the edge. With custom curtains, the panels are cut to your exact specifications — so the measurement you enter is the measurement you get. Getting the rod placement right first means your custom curtain width and drop will be accurate from the start.
Curtarra's curtains are made to order in the width and length you specify. If you mount your rod before measuring, you can calculate your panel size exactly — rather than guessing at standard lengths and hoping they fit.
Gary Linen Look 100% Blackout Curtains — a bestselling blackout panel at 270 GSM, suitable for a 1-inch rod. Custom width and length, machine washable. Shop Gary Blackout →
Lesley Linen Blend Curtains — a 339 GSM natural linen-blend panel that pairs well with a ¾–1 inch rod. Light-filtering and easy to care for. Shop Lesley Linen →
Frequently Asked Questions
How much wider than the window should a curtain rod be?
At minimum, 3 inches wider on each side (6 inches total). For a designer look that keeps the glass fully clear when curtains are open, extend 8 to 12 inches per side. The extra width allows the curtain panels to stack completely off the glass.
Should curtain rods be level with the ceiling or above the window?
Neither has to be wrong — it depends on your ceiling height and the look you want. For standard 8-foot ceilings, 4 to 6 inches above the window frame is the sweet spot. For taller ceilings, mounting closer to the ceiling makes the room feel grander. The key is consistency: all rods in the same room should be at the same height.
Can I measure for curtains before installing the rod?
You can estimate, but it's better to mount the rod first and then measure your drop from the bottom of the rod (or ring) to the floor. This gives you the exact panel length needed rather than calculating from a planned rod height that might shift slightly during installation.
What if my window is wider than standard rod sizes?
For wide windows over 96 inches, look for rods with a center support bracket — this prevents sagging in the middle. Custom curtain widths work well here since you can order wider panels to match without seaming multiple standard-width panels together.
Does curtain rod diameter affect how curtains hang?
Yes. A thin rod under heavy fabric will bow over time, disrupting the drape. A thick rod under lightweight sheers looks disproportionate. Matching rod diameter to fabric weight (see the table above) keeps both the look and the structure right.
Once your rod is measured and in place, ordering custom curtains at the exact width and length you need is straightforward. No guessing at standard sizes, no hemming afterward.
