Window coverings seem to be one of our most basic needs. As soon as you get some sort of shelter, you’re looking for a way to cover the windows for privacy. In college, I simply used push-pins to hold a sheet across my apartment’s bedroom window. I let it hang down at night, and during the day I held it back with a binder clip from my Economics textbook. Not very stylish, but at least it blocked the view of the dumpsters. Now I know window coverings are a great DIY project; and simple enough for the beginning sewer. Straight edges. Simple, straight stitches. The individual steps couldn’t be easier (check our our Curtains category). But even the most basic curtain project can go awry without some good planning. And the most important part of that planning is knowing how to take proper measurements.

We’re covering the basics here of outside, inside, and trim mounts. As with all projects, you can dive deeper into various details and alternatives, but this information will do the trick in the vast majority of situations.

Window covering measuring tools

• Retractable metal tape measure
• Step ladder or tall step-stool
• Chalk for marking the wall
• Pencil for marking the holes where your hardware will go

Step 1: Come up with your plan

Many a politician has accused his/her opponent of “already measuring for the drapes” – assuming he or she has won the election and is ready to re-decorate the office before a single vote has been cast. Maybe that’s not really an insult. It might be very useful to vote for someone who’s not only experienced at measuring for window coverings but also has the common sense to plan ahead.

Whether you hope to re-decorate the governor’s mansion or just cover a bedroom window, your first step is to come up with a plan.

You should be able to answer the following questions:

What function will the window coverings need to have? Is it to block out daylight? Let in light but give privacy? Or will they help cover an ugly view?

How do you want to make the room feel? A window covering will change the look of the window and so the look of the room. Do you want the window to look as big as possible or smaller than it is?

The answers to these questions will directly influence everything from your choice of curtain style to your choice of fabric and hardware.

For example, to make your window look as big as possible you want a wide outside mount: your hanging rod will be several inches wider and higher than the window molding. This will allow your curtains to open completely without blocking any of your window.

If you’re thinking about something like individual Roman shades, they will be about the same width as the window but mounted quite high so the bunched shade doesn’t block the view.

These kind of different considerations in style and usage are why pre-planning is so important.

Window coverings can also be a variety of lengths. You can have curtains that just touch the window sill or ones that hang all the way to the floor. Some people even like their drapes to puddle on the floor.

As you’re planning, determine if there are any obstructions that will get in the way of your desired length. For instance, if you have a baseboard heater below the window, your curtain should hang at least an inch above it.

Get some inspiration

Unless, you’ve already seen the ideal window covering in your dreams, look at as many examples as you can until you find one you really like. Of course, we like to think Sew4Home is great for this, but so is Pinterest as well as shelter magazines, design books, and commercial patterns for drapes and curtains.

Keep other windows in mind

Not only should your new window covering complement the coverings on the other windows in the room, they should also all hang from the same height. Windows that look like they should be the same height often aren’t. Measure to find the window whose top is highest from the floor. However high you hang its hardware will be the height for all the other window covering hardware in the room.

What type of mount do you want?

The most common mount is an Outside or Wall mount and this is what we show below in more detail. However, there are other options.

Inside Mount

You can use the inside mount for certain kinds of Roman shades or if you have beautiful decorative molding around your windows that you want to be visible. The hardware will mount just inside the edge of the window, along the inside edge of the trim. To calculate the fabric necessary for this mount, you will need to subtract the width of the trim from your original window measurements. You may find it easier to measure specifically for the Inside Mount. Run your tape from the inside edge of the molding to the opposite inside edge of the molding.

Trim Mount

This mount is a good option if you’re hoping to draw attention to the actual size of your window and/or if you want just a bit of the trim to always be visible. When using this mount, you’ll place the hardware directly on the molding on either side of the window. To calculate yardage for this mount, you will just use the measurements you took for the actual window, because these original raw measurements included the trim. There are purists who will scream you should never screw or drill into your trim as it can leave unsightly holes if the mounting hardware is ever removed. Duly noted, but it’s really up to you, and if it’s the best look for your room, this is a perfectly acceptable mounting option.

Sketch out your plan

Get the raw measurements of your window. Start by measuring the width of the window. Place the end of your tape measure along the outside edge of the molding of the window (not along the glass) and measure to the opposite outside molding edge of the window.

To measure the height of your window, place the end of the tape measure along the top edge of the molding of the window, and measure to the top of the window sill.

With these raw measurements, use a pencil and paper make a drawing of your window. Sketch in where you think you’d like your hardware and curtains. Keep this sketch handy as you do your measurements, because it’s going to be where you write down your dimensions.

Step 2: Mark Up The Wall

Once you’ve decided on the style and length of your window coverings, it’s time to get some real measurements. As mentioned above, we are using the Outside or Wall Mount as our example.

You definitely want to use a step ladder or a step-stool that’s tall enough to get you eye level with the top of the window. Reaching waaaaay up to mark is more difficult, and because of your angle of view, it can add inaccuracy to your markings.

It’s also a really good idea to get someone to help hold the end of the tape measure for you so you can get the most accurate mark possible.

Mark your hardware height

With a piece of chalk, mark on the wall above the window molding where you want your hanging rod to go. Measure and mark both sides of the window because not every window, especially vintage windows, are 100% square. As mentioned before, this new rod should be the same height as the other existing window treatments in the room. If you’re not matching to anything, then 2″- 4″ above the molding is standard.

Mark your hardware width

How far to either side of the window do you want your hanging rod to extend? This will be based on fabric weight as well as general look and feel; eg. how big you want the window to appear. Very heavy fabric can bow a long rod; either narrow your span or add a brace to the center of the rod. Mark each side of the window. Then write it on your piece of paper where you sketched out your plan. If you don’t have anything to follow, 3″ to either side of the trim is a common standard.

Step 3: Install Your Hardware

It might seem funny to screw your curtain hanging brackets into the wall before you’ve even measured for your fabric, but with the actual rod in place you have a real-world height and width to work from.

According to your hardware installation instructions, carefully measure where the screws should go so your hanging rod is placed at your intended height and width. If at all possible, get someone to help you hold the hardware in place for marking and to make sure that it’s really going to end up level and in the right place.

As with any hanging you do in your home, screw or drill into a stud if possible. If this isn’t possible with your chosen height and/or width, you may need an additional fastener, such as a molly bolt or toggle bolt to act as a hollow-wall anchor.

Step 4: Measure For Your Window Coverings

As you take your measurements, write them down on your plan sketch. This will help you remember them and better visualize as you measure your fabric.

Measure for different curtain styles

Floor length

Measure from the hanging rod to ½” – 1″ above the floor. Be sure to measure from both ends of the rod. If the floor is uneven, you don’t want one side buckling because it’s touching. In this case use the shorter measurement for both. As mentioned above, puddling drapes onto the floor is a trendy look. The longer you make the drape past the floor measurement, the bigger the puddle.

Apron length

Measure from the hanging rod to 2″ – 4″ below the “apron” (the part of the sill that sticks out like a shelf). The exact length will depend on the width of the base molding under the apron; you want the curtain to just cover this.

Sill length

Measure from the hanging rod to ½” above the apron. You want the hem of the curtain close but not touching. As with the floor length, measure both sides. If they’re different, take the shorter length.

Step 5: Calculate Your Fabric Measurements

Fabric width

Depending on the thickness of the fabric you’re using and how full you want your curtains, you can determine the width of fabric necessary for your curtains. For most curtains, two to two-and-a-half times the width of the window will be a good calculation. However, if you are using a very sheer fabric, you may want to multiply the window width by three or more. Conversely, heavy fabrics may only require one-and-a-half times the width of the window.

If you are planning to use more than one panel to cover your window, the width should be the combination of all the panels added together. For example, if your window is 40″ wide, you could create two panels, each 40″ wide when finished. When closed together to meet in the middle, you have a total of 80″ of finished curtain to cover the window – two times the window width for a nice gathered finish.

Fabric length

You want your fabric to be the actual length of the drape – whether it hangs from rings or has the rod go through a “pocket” – plus about 4″ for hems and casings at the top and another 2″- 4″ for hems at the bottom. The bottom hem is the often one you’ll sew last, which will give you a little room for adjustment. We usually recommend at least an extra half yard over the finished length just to be safe

For fabric with especially large or dominant motifs, once you have the yardage calculated, get enough extra yardage to complete at least one additional FULL repeat. This may seem like overdoing it, but it’s always better to have enough to work with to get a wonderful cut for your curtain panels. You can always use any leftovers for some beautiful coordinating pillows.

Now that you have your measurements, you’re ready to purchase your fabric and get started on your window covering project.

Measuring for drapes is all about thinking about what you want well in advance, and then taking time to think through each possibility. If you’ve done your measuring thoroughly and accurately, the actual sewing part should be a breeze.