How to Measure Curtains for a Patio Door: Step-by-Step

To measure curtains for a patio door, you need three numbers: the width of the area you want the curtains to cover, the height from your rod down to the floor (or wherever you want them to end), and the rod length. If you want a step-by-step guide for making them yourself, use this overview on how to make patio door curtains. For an outside mount on a standard sliding glass door, that usually means measuring the full door frame width, adding 6 to 10 inches on each side for stack-back clearance, then measuring from your rod position (typically 4 to 6 inches above the frame) down to about half an inch off the floor. From those numbers you can figure out how many panels to buy and what rod length you need. The sections below walk through every step.

Choose the curtain style and where it mounts

Before you pull out a tape measure, decide two things: the curtain style (rod pocket, grommet, pinch pleat, tab top) and where the rod or track will live (wall above the door, ceiling, or inside the door recess). These choices change what you measure and where you measure it from, so skipping this step leads to ordering the wrong size.

Outside mount (rod or track on the wall or ceiling above the frame) is the most common choice for patio doors. It gives you better light and draft control because the fabric can overlap the frame edges, and it makes the door look taller and wider. Inside mount (rod inside the door recess) works only if your recess is deep enough to mount hardware without the curtain catching on the door itself, which is rare on most sliding glass doors. For almost every sliding glass door situation, outside mount is the right call.

Your curtain style also affects where your height measurement starts. Grommet panels hang from the top of the rod, so you measure from the rod down. Rod-pocket panels sit on the rod and hang slightly lower, so the fabric top sits at rod level but the hang point is the same. Pinch-pleat panels on rings hang from the bottom of the ring, meaning they sit a bit lower than the rod. Know your header style before you finalize the height number.

Measure the patio door width

For an outside mount, you're not measuring the glass or the door panel itself. You're measuring the full frame or trim width, then deciding how far past that you want the rod to extend. Measure the outside edge of the left trim to the outside edge of the right trim. That's your frame width baseline.

From there, add clearance on each side. For a sliding glass door, you want the rod to extend 6 to 10 inches beyond the frame on each side. This does two things: it lets the curtain stack off to the side when the door is open without blocking the glass, and it gives you visual breathing room so the curtains don't look squeezed against the wall. A standard 6-foot (72-inch) sliding door with 8 inches of clearance on each side needs a rod that's at least 88 inches wide. Don't forget to subtract the finial length from each end when shopping for rods, since finials don't hold fabric.

For an inside mount, measure the inside width of the door recess at three points: top, middle, and bottom. Use the smallest of those three measurements. Most hardware manufacturers will deduct about a quarter to half an inch from your inside measurement to ensure the rod or track fits without forcing it.

If you have a track-mounted system (a ceiling-mounted or wall-mounted traverse rod rather than a decorative rod), measure the track's usable length, not including any fixed end stops. That's the number you'll use for your fabric math.

Measure the patio door height

Height measurement has two parts: where the rod goes, and where the curtain bottom ends. Decide the rod position first. For an outside wall mount, place the rod 4 to 6 inches above the top of the door frame or trim. If you're going all the way to the ceiling for a dramatic look, mount the rod 1 to 2 inches below the ceiling. Mark that point on the wall with a pencil.

Now measure from that pencil mark straight down to your desired endpoint. There are three common finishes:

• Half an inch off the floor: the cleanest, most practical look for a patio door that gets regular use. Fabric won't catch underfoot or snag on the door.
• Brushing the floor (about a quarter inch of contact): a slightly relaxed look that still reads as intentional.
• Puddle (3 to 6 inches of extra fabric on the floor): a formal, dramatic look that works better on fixed panels than on ones you'll open and close frequently.

For most patio door setups where people are walking in and out, the half-inch-off-the-floor finish is the most practical. Write that measurement down as your finished panel length.

One more thing: adjust for your header style. Grommet panels hang with the top of the grommet on the rod, so the top of the fabric is essentially at rod level. Rod-pocket panels sit on the rod and may drop the fabric top slightly. If you're using rings with clips or pinch-pleat hooks, add the ring drop (usually 1 to 1.5 inches) to your panel length, because the fabric hangs below the rod by that amount. This is a small but important detail that causes a lot of returns.

Account for coverage details

Width coverage is where a lot of people underestimate and end up with curtains that let light leak around the edges. The rod extending 6 to 10 inches past each side of the frame isn't just for looks: when the curtains are closed, the panels need to fully cover the glass and overlap each other in the middle by at least 3 inches so there's no light gap at the center seam.

On the sides, the fabric panel should reach to (or slightly past) the wall or trim edge of the door. If your rod extends 8 inches past each side of the frame, the curtain panel on that side should cover those 8 inches when closed. If you're stacking curtains open to one side (a common choice for sliding doors where you always open the same panel), plan for more clearance on the stack side so the door glass is fully exposed when open.

Also think about rod projection, which is how far the rod brackets stick out from the wall. You want at least 3 to 5 inches of projection so the curtain fabric clears the door handle and doesn't catch on it every time someone opens the door. If you're putting curtains over a door with a protruding handle or lock, measure the handle depth from the wall and add an inch. Standard brackets usually project about 3 inches, but double-check before buying.

Measure for inside mount vs outside mount

Here's a side-by-side summary of what changes between the two approaches:

If you do go inside mount, measure the recess depth too. You need at least 2 to 3 inches of depth for most rod brackets. Most sliding door frames don't have that, which is why inside mount rarely works here. If yours does, make sure the curtain fabric won't drag on the door panel as it slides.

Convert measurements into what to buy

Once you have your rod length and finished panel length, you can figure out exactly what to order. Here's how the math works.

Rod or track length

Your rod length equals the full span you measured (frame width plus side extensions). If your door frame is 72 inches wide and you're adding 8 inches per side, you need a rod that spans at least 88 inches. Round up to the next available size and use adjustable brackets to fine-tune the position.

Total fabric width (fullness)

Curtains need more fabric than the rod length to look full rather than flat. The standard rule is 2 to 2.5 times the rod length for a gathered or pleated look. For a sleeker, more modern look with grommet panels, you can go as low as 1.5 times. Multiply your rod length by your fullness factor to get your total fabric width.

Example: 88-inch rod at 2× fullness = 176 inches of total fabric width needed. If you're buying two panels, each panel needs to be 88 inches wide. Most store-bought panels come in widths of 50 to 54 inches, so for an 88-inch rod at 2× fullness you'd actually want three panels (or look for wider panels labeled 84–96 inches wide). Always check the panel's listed width, not just the length.

Number of panels

Divide your total fabric width by the width of the panels you're considering. Round up to the nearest whole number. For a patio door, two panels is the most common configuration (one stacks to each side when open), but a wide door with high fullness may need three or four panels. If you're doing a single-stack setup where all curtains pull to one side, that side needs enough clearance for the full stack, which is typically about 40 percent of your rod length.

Panel length

Use the finished length you measured (rod to floor minus half an inch, for example). Store-bought panels come in standard lengths: 63, 84, 95, 96, 108, and 120 inches are the most common. Pick the next size up from your measurement, not the nearest one down. You can always have panels hemmed shorter; you can't add fabric back.

Quick reference: measurement-to-panel conversion

Record your measurements properly

Write everything down in a simple format before you start shopping. You'll thank yourself later, especially if you're comparing options online. Here's what your notes should include:

• Frame width (outside trim edge to outside trim edge): _ inches
• Side extension per side: _ inches (typically 6–10 inches)
• Rod length needed: frame width + (2 × side extension) = _ inches
• Rod mount height above frame: _ inches above trim
• Floor-to-rod measurement: _ inches
• Desired finish (off floor, brushing, puddle): _
• Finished panel length needed: floor-to-rod minus finish adjustment = _ inches
• Standard panel length to buy (next size up): _ inches
• Total fabric width needed: rod length × fullness factor = _ inches
• Number of panels needed: total fabric width ÷ panel width (rounded up) = _
• Rod projection from wall needed: _ inches (at least 3–5 inches for patio door handle clearance)

Common mistakes and a quick re-check

The most common errors are measuring the glass instead of the frame, forgetting to account for fullness (so the curtains look flat and thin), and choosing a panel length that's an inch or two short so the curtain floats awkwardly above the floor. If you want to avoid that common sizing mistake, follow these steps for how to measure for a sliding patio door before you order anything measure the glass instead of the frame. Here are the ones I see come up again and again with patio door curtains specifically:

1. Measuring only the door panel width, not the full frame. Your rod needs to clear the entire frame plus stack-back space.
2. Forgetting the center overlap. Two panels on an 88-inch rod need to overlap by at least 3 inches in the middle, so factor that into your fabric math.
3. Not accounting for ring or hook drop. If your rings add 1.5 inches of drop below the rod, your panels need to be 1.5 inches shorter than your floor-to-rod measurement, or they'll puddle unintentionally.
4. Buying panels that are too narrow and skipping the fullness calculation. A 52-inch panel on an 88-inch rod covers the rod but looks flat and sad. Do the 2× math.
5. Ignoring rod projection. If the bracket only sticks out 1.5 inches from the wall, the curtain will drag on the door handle every time someone uses it.
6. Not measuring three times for inside mount. Recess walls are rarely perfectly parallel, so always take top, middle, and bottom width measurements and use the smallest.

Re-check before ordering

Run through this quick checklist before you click buy:

• Did you measure from the rod position, not the top of the door frame?
• Is your rod length based on the full coverage area (frame + side extensions), not just the door width?
• Did you calculate total fabric width using a 2× to 2.5× fullness factor?
• Does the number of panels give you enough fabric to hit that fullness number?
• Is your chosen panel length the next standard size up from your measured drop?
• Have you confirmed the rod projection is deep enough to clear the door handle?
• If using rings or hooks, did you account for the drop distance in your panel length?

Once you've got these numbers locked in, you're in good shape to shop. If you're working through the rest of the project, you may also want to look at guidance on how to hang patio door curtains once they arrive and how to install the curtain rod correctly, since mounting hardware on a patio door frame has its own quirks. Getting the measurements right is the hard part; the rest is straightforward. Once you have the measurements nailed down, installing the patio door curtain rod is the next step install patio door curtain rod.