How to Measure for Custom Curtains: Windows, Patios, Pergolas & More

Measuring for curtains looks simple. But this tiny thing determines the overall look of your curtains. You might think you don’t need a guide for it. But this most ignorant part, the measuring, which is where most of the output goes sideways. It is the size of the curtain which is of utmost importance, not the fabric choice, not the color, not the hardware, but only the right size matters. If one number is off by a couple of inches, the whole thing goes wrong.

Have you been there, done that? Does that end up in frustration with visually unappealing curtains? So, it is important to know how to do it properly. And the good news is, once you understand the logic behind each measurement, you understand how it affects. Then, the whole process becomes straightforward.

This curtain measurement guide on how to measure for custom curtains covers every indoor and outdoor setup, including standard indoor windows, outdoor patio setups, gazebos, pergolas, and more. 

What You'll Need To Determine The Right Custom Curtain Sizing

Always make sure to take accurate measurements to get the right custom curtain sizing. Accurate measurements save you from problems like curtains collecting dust on the floor or hovering over. So, always measure right, and for that you need:

• A metal or flexible fabric tape measure — rigid folding rulers don't follow curves or reach awkward angles well
• Something to write with — a phone notes app works fine
• A stepladder if your windows or pergola beams sit high
• An extra pair of hands for anything wider than 8 feet

One rule that applies everywhere in this guide: measure at least twice. Custom curtains are cut to your dimensions. There's no adjusting them after the fact. 

Measuring Windows For Curtains

First, Decide How You Want the Curtain to Mount

There are two options: inside mount (the curtain sits within the window frame) and outside mount (the rod goes on the wall above and around the frame). This matters because your measurements change depending on which you choose.

Outside mount is more common for custom curtains — it makes windows look larger, gives you better light control, and tends to look more intentional. If you're not sure, outside mount is the safer starting point.

Measuring the Width

For outside mount, start with the width of the window frame itself. Then add 4 to 8 inches on each side — this extra width is what lets your curtains hang open without blocking any of the glass, and it gives the panels room to gather properly.

So if your window frame measures 36 inches across, your rod should span somewhere between 44 and 52 inches total. The curtain panels you order need to cover that full span with some fullness.

For inside mount, measure the exact interior width of the frame from wall to wall. No extra is needed.

Measuring the Drop Length

Measure from where the rod will sit — not from the top of the window frame, and not from the ceiling. If the rod isn't installed yet, mark where it will go first, then measure from that point down.

Where you want the curtain to end is a personal call. Here are the four standard options:

• Sill length — ends at the bottom of the windowsill. Casual and practical, good for kitchens
• Below sill — 4 to 6 inches past the sill. A clean middle ground that works almost anywhere
• Floor length — half an inch above the floor. The most common choice for living rooms and bedrooms
• Puddle length — 2 to 4 inches of extra fabric on the floor. Intentional and dramatic — only if you want that look

A Quick Note on Fullness

Custom curtains are ordered by panel width, not rod width. For curtains to look full and draped rather than flat and stretched, you generally want the total panel width to be 1.5 to 2 times the rod width. Your curtain maker will help you work this out, but it's useful to know before you get to that conversation.

Outdoor Curtain Measurement: Measuring for Outdoor Patio Curtains

Outdoor curtains do different work than indoor ones. They're blocking afternoon sun, giving you privacy, softening the wind, or just making the space feel more like a room. The measuring logic shifts a bit.

Width

Measure the full span you want to cover — post to post, wall to wall, or wherever your rod or cable wire will mount. Then add at least 6 to 12 inches on each side for overlap when the panels are closed.

This overlap matters more outdoors than it does inside. Wind will find any gap and billow the curtains open. A generous overlap keeps things looking neat and actually functional. For fixed-width curtains, count the number of panels you need. 

Patio Curtain Height Guide: Drop Length Determination

For most patio setups, floor-length is the right call. Measure from the underside of your mounting track or rod straight down to the floor or deck surface, then subtract 1 to 2 inches so the fabric doesn't drag.

One thing that catches people off guard: if you're mounting on a wall bracket rather than a ceiling track, measure from the bracket position — not from the ceiling. It's a small distinction that makes a real difference in the finished length.

Multi-Bay Patios

If your patio has multiple sections — say, three openings across a covered porch — measure each one separately. Even openings that look identical often aren't, especially on hand-built structures. A few inches of difference per bay adds up, and you don't want curtains that fit four out of five openings.

Pergola Curtain Dimensions: Measuring for Pergola Curtains

Pergolas are some of the most rewarding spaces to dress with curtains. When it's done right, the transformation is genuinely impressive — an open structure becomes something that feels like an outdoor room. But getting the measurements right requires a bit more attention than a standard window.

Width Per Bay

Measure each bay individually — that's each opening between posts or beams. On hand-built or older pergolas, bays that look equal rarely measure the same. Add 6 to 10 inches on each side of each opening for overlap so the panels close fully and sit without gaps.

Drop Length

Pergola curtains are almost always floor-length. Measure from the top beam — wherever your rod, tension wire, or track will sit — straight down to the ground or deck surface. If the pergola sits on a raised deck, measure to the deck surface itself, not into any gaps between the boards.

Attachment Style and Its Effect on Drop

How the curtain attaches to the rod affects how long it actually hangs:

• Grommet-top panels hang 1 to 2 inches shorter than the ordered length because the grommet ring sits on the rod, not above it
• Tab-top panels hang slightly lower, depending on the tab length
• Rod pocket panels hang close to the ordered length
• Clip rings add a few inches to the total drop

Decide on your attachment style before you finalise your measurements, and factor in the difference.

Thinking About Tie-Backs

If you plan to tie back the curtains during the day, order your panels a bit wider than the opening. Panels that are pulled back look beautiful when there's enough fabric to gather — they look sparse when the panels are just barely wide enough to cover the opening in the first place.

A Few Other Spaces Worth Knowing

Covered Porch or Verandah

Treat each opening between columns or posts as its own measurement. If the porch wraps a corner, measure each run separately — the measurements for each section are independent, even if the hardware connecting them isn't.

Gazebo Curtains

Most gazebos have multiple equal-width openings. Measure one, confirm it matches the others, and order matching panels. Drop length is typically floor-length, the same as pergola panels.

Sliding Glass Doors

Measure the full door opening width, then add at least 12 inches on each side so the panels can stack back off the glass when the door is in use. Floor-length, or just above it, is standard.

Your Pre-Order Checklist

Before you submit your order, check off each of these:

• Width measured at the widest point, with your overlap allowance included
• Drop measured from the rod or mounting point — not the ceiling or window frame top
• Mount type confirmed: inside vs outside (windows), or post-to-post (outdoor)
• Attachment style decided, and drop length adjusted accordingly
• Number of panels noted for each opening — single or double
• Each bay or opening is measured individually, not assumed equal
• Everything is measured at least twice

A Couple of Things That Often Catch People Off Guard

The most common one: confusing rod length with panel width. They're not the same thing. A 60-inch rod needs panels that total somewhere between 90 and 120 inches wide to look full. If you order panels that just cover the rod, they'll look flat and stretched.

The second one: not accounting for how the curtain will actually be used day-to-day. A curtain that stays closed can be ordered to span exactly. But if you're opening and closing it regularly, you need extra width in the panels so they stack neatly to the sides without eating into your view or light.

And outdoors specifically: keep curtains 1 to 2 inches off the ground. Fabric that drags on a deck collects dirt and moisture quickly, and that shortens the life of even a high-quality panel. It's a small thing that makes a real difference over time.

Once Your Measurements Are Ready

The next question is usually fabric — and outdoors, that choice matters a lot more than it does inside. Learn Why Sunbrella is The Best Choice for Patio Cushions, Curtains & Throws: The Complete Spring Guide. 

If you're leaning toward Sunbrella fabric — which comes up a lot for outdoor curtains, explore ZIPCushions’ Sunbrella curtains here.

That's Really All There Is to It

Measuring for custom curtains doesn't require any special skill — just a bit of patience and the willingness to measure twice before you order once. Get those numbers right, and everything else falls into place.

If you run into a space that doesn't fit neatly into any of the steps above — an awkward angle, a non-standard bay width, or a structure that was clearly built without a tape measure nearby — just get in touch before you order. A photo and your measurements are usually enough to work it out together.

Take your time with the measuring. The curtains will be worth it.

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Frequently Asked Questions About Custom Curtains 

1. How do you measure your windows for curtains for fixed width curtains? 

For a standard panel curtain (the width of which is fixed), measure the total rod width. And then multiply it by 1.5x to 2.5x fullness. After that, measure from the rod to the desired floor or sill length. Standard recommendations ask to install the rod 4 to 10 inches above the window. And, extending it 6 to 12 inches on each side to make your windows look larger and to maximize light. 

2. Should patio curtains touch the ground? 

An individual's preferences differ for whether their curtains should touch the ground or hang slightly above it. However, for busy areas like kitchens and living rooms, keeping them slightly above the floor is a practical choice. 

3. What is the current trend for curtains? 

Present drapery trends feature matte finishes and natural and subtle colors. The header style, however, can have different options, based on your use and preference. They can have rings, hooks, grommets, tab top, or else. Do check for header style options and decide based on the location where you want to place them. 

4. What color curtains match everything? 

For a blend-in look, neutral options like light gray or beige work well. These colors seamlessly blend with your walls and furniture colors. However, for a standout feel, choose bold colors like bright teal or deep red to make them the focal point of your setup. 

5. Should curtains be lighter or darker than the paint? 

Choose drapes a shade lighter than your wall paint to strike a balance between dark wall colors and light furniture. It ultimately depends on your room’s size, lighting in it, and the overall mood you want to create.