How to Measure an Entry Door for Replacement

Man measuring entry door for replacement

If you're in the process of replacing your entry door, or even upgrading all the doors in your home, it's important to have an understanding of how to measure your old and new doors.

Entry door dimensions, such as width, height, and thickness, must be accurate in order to allow for a smooth and easy replacement process.

Measuring a Pre-Hung Front Door

When measuring a pre-hung door, it is vital to know if you are replacing an existing one or installing one at an opening where there was no door previously. When measuring an empty opening, follow these steps:

1. Take width measurements

Place your tape measure on the inner stud of one side of the opening, then take the measurements along the stud on the other side. Take these measurements in several locations such as the middle, lower part, and the top of the opening, using the smallest value as your width.

2. Measure the height

Measure the height of the opening from the sill to the lower part. Take measurements of at least three spots, then use the smallest value as your height.

3. Determine the thickness

For any pre-hung door, you will need to take measurements of the wall opening rather than the frame itself.

Replacing an Existing Door with a Prehung Door

When replacing an existing door with a pre-hung one, follow these steps instead:

1. Remove the existing trim

Use a pry bar with a flat head, then pop out the trim to ensure you take measurements only from the door frame.

2. Check on the requisite width

Place a tape measure on one side of the outer jamb to measure the lower, middle, and top parts. Use the lowest figure of the dimension as your width.

3. Measure your height

Place your tape measure so that it runs from the upper jamb to the sill. If you are measuring an exterior door, start from the sill; for an interior door, take the measurements starting from the floor upwards. Take measurements of all three dimensions, then use the smallest figure as your height.

4. Find out the thickness

Place your tape along the inner edge of one side jamb all the way to the exterior edge. To get accurate dimensions, leave the outer trim out when taking measurements.

Measuring A Front Door with Sidelights

When measuring a front door with sidelights, follow these steps:

  1. Take measurements of the width of your exterior door. You can do this by measuring one side of the door panel all the way to the other side. Afterwards, measure the distance of the inside jamb on every side, then record the sidelight and exterior door values separately.
  2. Find the height of the door by measuring from the top of the door panel to the bottom edge. Then, take the height of the sidelight between the top jamb and the inside of the bottom jamb.
  3. Take measurements of the jamb depth and exterior door thickness.
  4. Measure the height and width of the door frame, then record the values.
  5. To determine if your door is level and square, take measurements of the door from one side of the corner to the equivalent opposite corner in an X pattern to check if the numbers match.

Measuring Double-Entry Doors

When measuring a double-entry door, follow these steps:

  1. Measure the width of the door from the outside of your home to the other side across all door panels.
  2. Take measurements of the double door from the top to the bottom edge of the door.
  3. Find the width of the door jamb and the thickness of the door by measuring the size of the wooden frame holding the door and the edge of the door, respectively. This process may require removing the trim surrounding the door, so make sure not to involve the trim measurements.
  4. Lastly, measure the door frame height and width. This can be done by measuring the inside edges of the trim from one end to another.

Measuring Double Doors with Sidelights

When measuring a double door with sidelights, follow these steps:

  1. Take measurements of the width of the exterior door, then record the values. Measure sidelight width through the inside of the jamb on all sides, then record the sidelight and exterior door values separately.
  2. Measure the specific height of the front door, starting from the top of the door panel to the bottom edge. Find the distance between the inside top jamb and the height of the sidelight to the inside on the bottom of the jamb and record the values separately.
  3. Measure jamb depth and door thickness. This process may require removing a trim section that surrounds the door. Do not use trim measurements.
  4. Finally, find the height and width of the door frame by measuring the inside of the trim and the edge of your home interior.

Frequently Asked Questions

How do I know what size exterior door to buy?

The easiest way to know which size exterior door to buy is to take measurements of the existing door's width and height. To gauge their values, ensure you measure all dimensions on every side, either along the door opening's top, bottom, or middle.

How much smaller should a door be than the frame?

Ideally, a door should be smaller than its frame by approximately 2 inches for every standard door. Measurements will also vary according to the door type and how they hang.

How do you measure an external door?

To measure the external door, start by measuring from the top of the door panel down to the very bottom edge of the door. Your measurements should include the door's thickness, height, and width, along with its frame values.