The Ultimate Sliding Door Measuring Guide

Pemko offers a range of sliding door options, including on-trend barn sliding door hardware to box track sliding door hardware. Any time you install sliding doors, you save space with a unique design aesthetic for your interior spaces.

Correctly measuring a sliding door is crucial to smooth and friction-free operation without any problems, but different door weights and heavy duty applications may require special tracks. Our guide will show you what you need to size your door for an easy installation.

How to Measure for a Sliding Door

We include a step-by-step guide to sizing your door as well as considerations for different styles of doors, which may need more overhead space or special track considerations. 

What You Need to Size Your Door (or Opening)

  • What application goes with the right hardware
  • Finished width and height of opening (see architectural plans)
  • Or the net width and height of the door

1. Identify the Right Hardware and Prepare Blocking

Before sizing your door, you want to make sure that the supporting structure can bear the weight of a sliding door. There should be blocking in place to attach the right hardware for your application. 

2. Sufficient Space

Door installation experts always consider the space around the opening and the clearance above it. This prevents problematic sight lines and ensures the door operates correctly. 

Depending on the hardware you choose, you’ll need enough clearance above the opening to install the track, Not all hardware is the same size, so be careful with your measurements and check that all sight lines are covered. 

In addition, the door must have enough empty space next to the door’s opening to accommodate the door as it slides open. If installing double doors, you’ll check that there’s space on either side of the opening to match the door size. 

Another common question distributors ask is: “Do you have enough wall space to the left or right of the opening to fit the selected sliding door and sliding track?”

If not, the space could look crowded and lead to difficulties with opening the door. 

Note for Residential Barn Door Sliding Doors (particularly for remodel construction): When remodeling a doorway, check for electrical outlets, light switches, and heat registers that might alter your door placement. 

3. Match Door Weight to Hardware System

Door weight is imperative when picking out the right sliding door system. If you’re not sure of the door’s weight, you can get a better idea by measuring the height and width of the door, as well as the thickness and type of door material.

Pemko Door Chart

Frequently used doors and commercial applications may require heavy duty steel tracks, particularly if you are using a heavy wooden door. 

4. Determine Door Size

It is recommended that the door overlap the opening by at least 2" on each side. this will help reduce sight lines as well as keep the guide covered and out of sight on the guide side of the opening.

Pemko also recommends at least 1" of overlap between the door and opening at the top of the door on side wall mounted track systems. Check for proper clearance at the top of the opening for the track and hardware.

As long as you have the wall space, it’s possible to add as much as a 4” overlap per side, as long as you are covering the minimum size of the opening. Don’t Forget the Undercut Either

For proper sliding door installation, check that there is space underneath the door for a frictionless operation. This is called the undercut, and it stands for the measurement of the gap. 

5. Remember These Equations

For those who know the opening size first, then these formulas are best to use to find the accurate door size:

To find the door width, simply use this formula:

  • Door width = Opening width + overlap

For the door height, use this formula for side wall mounted track systems:

  • Door height = (Opening height + door overlap) - undercut

When installing overhead mounted track systems, use this formula:

  • Door Height = Opening Height - Clearance for Hardware (at the top as well as the bottom)

However, if you know the door size but not the opening width, you’ll use these formulas:

  • Opening width = Door width - overlap
  • For side wall mounted systems: Opening height = (Door height - overlap) +undercut

Special Considerations for Sliding Door Sizing

There are also some considerations for different types of sliding doors. There are some variations with sizing these doors as follows: 

Pocket Doors

Pemko makes pocket door kits for 2x4 metal or wooden stud constructed walls, 2x6 wood stud constructed walls and 2x6 metal stud constructed walls.

For these doors, the rough opening formula is as follows:

  • Leave a space (do not stud) = (2 x Door Width) + 1”, Door Height + 5”

Note: Doors are ordered in net sizes. for instance, if the rough opening is 73" x 89" the door would be ordered net 3'0" x 7'0”

Bypassing Doors

These types of doors are used mainly for closets with two doors on two different tracks that can pass over each other. Bypassing doors use an overhead mounted system, typically called a case opening. 

  • Door width = Opening Width divided by 2; plus overlap

Your Sliding Door Questions Answered

Our Pemko team handles all types of sliding door installations--from commercial steel to barn sliding doors. How can we help with your sliding door installation and hardware? 

See more information on sliding door hardware, proper installation tips, and troubleshooting sliding door, or talk to a sliding door expert now