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How To Measure Your Front Entry Door


When first starting the search to replace your front door, it is always best to have a rough idea of the size you need to be focusing your search on, and if that size is a standard size or a custom unit.

We strongly recommend having a professional installer take the final measurements to ensure the proper fit of the unit.

When it comes to doors there are four different dimensions that are typically referred to:


Brick Opening/Masonry Opening  • 
Rough Opening  • 
Unit Size  • 
Door Slab Size

Brick Opening of the Front Door

The Brick Opening size of entry door is measured from the exterior side of the home from Brick to Brick.

This size the largest of the four and is the size that most people measure when changing an existing unit with a new unit.

The Brick Opening is typically about 2-1/2" wider and 1-1/4” taller than the Unit Size. Example is 40" x 82-3/4".

Entry Door Brick Opening

Rough Opening of the Front Door

The next size is the Rough Opening size of entry door which the 2nd largest dimension and typically widely talked about when referring to a new construction.

The Rough Opening is the space between the two wall studs the door unit will be attached to.

The Rough Opening is typically about 1-1/2” wider than the unit size and about a 1” taller.

The space that is left over will be used by the installer to shim and square the unit into place. Example 39” x 82-1/2”.

Entry Door Rough Opening

Unit Size of the Front Door

The Unit size of entry door is the external dimension of the frame on which the door slab it attached.

We use the Rough Opening and the Brick Opening dimensions to find out the proper Unit Size for each home. Example 37-1/2” x 81-1/2”.

Entry Door Unit Size

Door Slab Size

The unit size in turn, gives us the Door Slab size of entry door, which is the actual operating door. A typical frame is 1-1/2” wider than the nominal door slab size.

When talking about a door size most people refer to the nominal door slab size. Example 36” x 80”.

Entry Door Slab Size

Taking some rough measurements to figure out what unit size your home might need is always a good idea when starting out your door purchasing experience.

When it comes to making the purchase of your new door, we strongly recommend that the installer who will be installing the unit, confirms your measurements to ensure a proper fit.