Barn Door Size Guide: Find the Right Size for Your Opening

Barn door sizing works backwards from what you'd expect. With a traditional hinged door, you need a door that fits inside the frame. With a barn door, you need one that's bigger than the opening—sometimes significantly bigger.

Get this wrong and you'll end up with visible gaps when the door is closed, privacy problems in bathrooms, or a door that can't slide fully open because the track is too short. The good news is that sizing a barn door correctly comes down to a simple chart and a few basic formulas.

Below you'll find a quick-reference guide that matches common opening sizes to the right door and track dimensions. If your opening falls outside these standards, the calculation formulas will work for any size.

What Size Barn Door Do I Need? Opening to Door Size Chart

This chart covers the most common residential openings. Find your opening width in the left column, then read across for the recommended door and track sizes.

These recommendations assume a standard 2" overlap on each side of the opening. For bathrooms or anywhere privacy matters more, size up—a 32" bathroom opening works better with a 40" door than a 36".

Don't see your exact opening? The formulas below will help you calculate the right size for any measurement.

How Do You Calculate Barn Door Size?

Three formulas handle virtually every barn door sizing situation.

Door Width Formula: Opening width + 4" = Minimum door width

For bathrooms or privacy-critical spaces, use opening width + 6" instead. A 32" opening needs at least a 36" door—or a 38" door if it's for a bathroom.

Door Height Formula: Opening height + 1" = Door height

An 80" opening calls for an 81" door. The extra inch ensures coverage at the top while leaving room for the ½-1" floor gap at the bottom.

Track Length Formula: Door width × 2 = Minimum track length

A 36" door requires a 72" track (6 feet). This allows the door to slide completely clear of the opening when open.

The reason these formulas add extra width comes down to how barn doors work. Unlike hinged doors that sit inside the frame, barn doors hang in front of the wall. RealCraft's measuring guide explains: "If you have a door that is the exact same size as the opening, lots of light and sound will come through the edges."

Without adequate overlap, you'll also see straight into the room when looking at the doorway from an angle—not ideal for bedrooms or bathrooms.

One more tip: measure your opening width at three points (top, middle, bottom) and height at three points (left, center, right). Walls aren't perfectly square, especially in older homes. Use the largest measurement for each dimension to ensure proper coverage.

How Do You Size Different Barn Door Configurations?

The sizing rules change depending on whether you're installing a single door, double doors, or a bypass system.

• Single Barn Door: This is the most common setup. The door slides to one side when open, requiring clear wall space equal to the door's width. Use the standard formula: opening + 4" = door width, and door × 2 = track length.
• Double Barn Doors: Two doors meet in the middle, each sliding to opposite sides. Calculate each door as: (opening width ÷ 2) + 2-3" overlap per side. A 60" opening works well with two 32-34" doors. You'll need clear wall space on both sides of the opening.
• Bypass Barn Doors: These slide past each other on parallel tracks—useful when you don't have wall space beside the opening. Each door should fully cover the opening width, with about 2" of overlap where they meet in the middle. According to Dusty's Rustic Rolling Doors, single-track bypass systems have roughly 4¼" of built-in overlap between doors.

Quick decision guide:

• Standard doorway with wall space on one side → Single door
• Wide opening (5 feet or more) → Double doors
• Limited or no wall space beside opening → Bypass system

Should You Measure to the Trim or the Opening?

This detail trips up a lot of first-time barn door buyers—and the answer depends on your door frame.

If your opening has trim or casing: Measure from the outside edge of the trim on one side to the outside edge on the other. Add 2" total (1" overlap per side). The door will fully cover the trim when closed, creating a clean look.

If your opening is sheetrock only (no trim): Measure the raw opening width and add 4" total (2" overlap per side). The extra overlap compensates for having no frame to hide behind.

Just remember that your wall trim usually isn't square. Sizing up to cover these irregularities means they won't be visible once the door is installed.

What Are the Most Common Barn Door Sizing Mistakes?

Five errors account for most barn door returns and installation headaches.

1. Door matches the opening exactly. A 36" door on a 36" opening leaves gaps on both sides. You'll see light around the edges and hear everything from the next room. Always add at least 4" to your opening width.

2. Measuring only one spot. That opening might be 32" at the top and 32.5" at the bottom. If you ordered based on the top measurement, the door won't fully cover the wider section. The best way to do this is by measuring three points for both width and height, then using the largest number.

3. Track too short for the door. The track needs to be twice the door width—not twice the opening width. A 40" door on a 72" track won't slide fully open, leaving part of the doorway blocked.

4. Forgetting to check wall space. Before ordering, verify you have clear wall beside the opening equal to your door width. Light switches, outlets, vents, and windows all interfere with the door's travel path.

5. Ignoring floor variations. Floors aren't perfectly level. If you set your door height based on one spot, it might drag where the floor is higher. Measure along the entire path the door will travel and maintain ½-1" clearance at the highest point.

Do You Need Standard or Custom Sizing?

Most openings work with standard barn door sizes—30", 36", or 42" wide in heights of 80", 84", or 96". These ship faster and cost less than custom options.

Custom sizing makes sense when your calculated door size falls awkwardly between standards, when you have vaulted ceilings or extra-tall openings, or when you want a specific look that standard dimensions can't achieve. Expect to pay 20-50% more with longer lead times.

The practical reality: a 32" opening pairs perfectly with a standard 36" door. A 34" opening works with either 36" or 42", depending on how much overlap you want. You often don't need custom—just round up to the next standard size.

Getting Your Size Right

The chart at the top of this guide handles the most common situations. Find your opening, read across, and you've got your door and track dimensions. For anything unusual, the formulas work for any opening size.

Once you've determined your door size, you'll need hardware rated for the door's weight and a track that matches the length you calculated. 

The Barn Door Hardware Store carries complete kits across all standard track lengths, with options for everything from lightweight closet doors to heavy reclaimed wood installations. 

If your opening falls outside typical dimensions or you're unsure which configuration works best, their team can help match door size to the right hardware.