Black Rail Hardware for Barn Door

Measuring Barn Door Rail Size Guide

When selecting a sliding barn door, the buyers are often hit with a crucial question: what should be the barn door rail size? Most people are confused when it comes to measuring track size for a barn door as it significantly differs from measuring for a traditional swing door. 

Even if both doors have the same size opening, the size of the doors will be relatively different. This is because a swinging door fits the door opening entirely. However, since a barn door has several moving pieces, you will need a door that is a bit larger than your door frame. Otherwise, lots of light and sound will penetrate through the edges of your door when it’s closed. Hence, we have crafted this comprehensive yet simple guide to help you pick the right barn door rail size for your room!

Prerequisites for measuring barn door rail 

Before we get into the hows of measuring a barn door track, it’s important to understand the following things:

  1. First, make sure the space over the opening is sturdy enough to support the weight of a hanging door. The place where you want to install the sliding track must have strong support beams to anchor the door. And the space between the top of the opening and ceiling should be sufficient (at least 6-inches) to install the door effortlessly.
  2. Second, you have to ensure that there are no light switches and electrical outlets near the sliding door that could interfere with its opening.
  3. Next, understand whether your door opening has molding or not. A molded door features a trim that goes all the way around, whereas a non-molded door opening includes a traditional sheetrock opening. 
  4. Finally, measure the width and height of the barn door because the track size depends on these two parameters. Measuring the length of the door is equally important as an inaccurate measurement will cause the door to stick with the floor, damaging it and making the sliding operation difficult. 

Measuring barn door rail in five steps

You will need a tape measure or ruler, stool, pencil, and paper to measure the barn door rail.

Step 1: Measure door space to ceiling space

You need to measure the space between the ceiling and the top of your door frame to confirm the space is enough to position the track and install the door hardware. For this, take a measuring tape and measure the distance from the top of the molding/door frame to the ceiling.

Step 2: Measure the wall

As mentioned already, you need ample wall space to ensure that your barn door will slide out of the way completely when you need to open it. To analyze if you have gotten the right wall space to install a barn door, make sure the wall space on either side is double the width of the door opening. 

Step 3: Determine the door width

Measuring the door width is essential to ensure privacy and aesthetics. If your door doesn’t overlap the side of your opening, it will fail to protect your room from excessive light and sound. The more overlap, the better protection. However, we recommend at least a one-inch overlap on each side. 

Here’s how you can measure the width of a molded and non-molded door opening:

Molding: For a molded door opening, you need to buy a door that is wide enough to cover the molding. To determine the width, measure horizontally from the outside edge of the molding on one side to the outside edge of the other side of the door. This is a suitable measurement, but you can go further from this to create a different style. 

Remember the wider door you select, the more wall space and track length it will need to function properly. Also, make sure that the molding doesn’t stick out more than 1” from the wall because if it does, the barn door will not fit the door opening appropriately.

Without molding: If your door opening doesn’t have molding, measure the horizontal width and add a few inches to this measurement (2 to 4 inches). This will be your minimum door opening width without molding. Now you might be thinking about why you need to add extra inches to your door width. This is because adding a few inches to your door eliminates the space between the door and the wall, blocking the sight line and thus offering more privacy. 

Also, if you have a light switch or any register on the wall, the extra cushion will cover it for you. So, if you have a 38 inches wide door opening, your barn door must at least be 40 inches wide (38” + 2” = 40”). 

Step 4: Record the rail length

Essentially, your rail length must be twice the size of your door width. This will let you completely uncover the entrance when needed. Plus, you can add 4 to 6 extra inches for a smooth and safe barn door operation. For the most precise rail length measurement, use the following equation:

(Width of door x 2) + (4-6” space) = minimum rail length 

For example, if you have a 38” wide door, the track length for your door must be 76”: 38” + 38” = 76”. However, if you have extra space on your banked wall, consider adding 4-6 inches in the measurement. 

Step 5: Measure the door height

Once you have decided on the rail size, your next step should be to know where you want the rail mounted. Generally, you can locate the top of your barn door a few inches above the door frame, so your door hangs at least one inch from the floor. This extra space between your door and floor is crucial to ensure the door glides effortlessly without sticking or swinging. While this measurement is suitable for mounting most door tracks, it’s still important to measure the door height to tackle slight variations in molding and unmolded door openings.

Molding: Measure from the floor to at least 1” above the outside edge of the molding frame and then subtract half an inch. 

Without Molding: To calculate the height of a door for an unmolded door opening, take the measuring tape from the floor to at least one inch above the door opening, then subtract half an inch.

As informed earlier, this half an inch space is important to account for minor variations in floor height or uneven floors. If your floor is carpeted, we suggest you subtract more than ½” to make sure the carpet doesn’t create an obstacle while sliding the door. However, be cautious about your spacing decisions because too much gap between the floor and the door will result in an unappealing gap. 


Determining the correct rail size for your barn door is a significant aspect of creating an aesthetically pleasing door entrance. You would be happy to know that the above measurements for a single barn door will also suffice for double barn doors. While the detailed steps are easy to follow, measuring for a sliding barn door could be tricky. So, make sure you follow all the steps accurately or call experts for help if you are not confident about your measurements. And once you have the exact measurements, head on to our website,, and shop for a barn door that best suits your home style.