When choosing an exterior replacement door for your home’s entry, it’s important to take the right measurements to ensure a proper and level fit. Partner with a professional custom door installer in New Jersey that knows how to replace an exterior door. This will allow you to avoid any unforeseen problems that can occur during the installation process. This will be especially true if your home may have walls and floors that are not level, door framing that needs repairs, or screw holes that are loose or stripped.

There are a number of reasons why you need to take accurate measurements before you shop for a new door. One being that older homes may have a larger door opening when compared to the standard, modern exterior door size which is 80 inches by 36 inches or 6 ft – 8 inches by 3 ft. And sometimes, newer homes will feature smaller doors that are either 30 inch or 32 inch wide.

You will also find many homes with doors that are both taller and wider than the standard – from 7 or 8 feet tall with widths that range from 24 to 42 inches. And when it comes to steel or fiberglass doors, you will find a smaller selection of door size choices as these specialty doors are commonly fixed at at 6 ft – 8 inches tall or 8 feet tall.

If you are wondering what size door do I need to replace an exterior, residential door, there are two things you need to know. You need to know the critical measurements to take and know how to measure a door opening. If you can accomplish these two tasks, you won’t need to use a door measurement calculator or rely on your door installation contractors to measure your door.

How to Measure Your Front Door

This will depend on the style of door you will be replacing. Of course, you will need accurate door height and door width measurements, along with the door thickness. But, if you have an architectural style door with an arched or round top, there will be additional measurements to take.

After you successfully measure your current exterior door, make sure you tell your new door provider that the measurements were not taken by a contractor and make it clear what each measurement represents. There are a number of ways doors can be measured in height and width by a contractor and will usually involve one or more of these methods.

  • Slab measurement – the height and width of the door opening without any frame or hardware.
  • Finished opening – the height and width of the door from the floor to the upper frame trim.
  • Rough opening – the size of the hole that is cut in the wall, which is not always square, and is typically about 1-1/2” wider and about a 1” taller than the finished door opening.

Each door manufacturer will have its own standards that might cause the actual door measurements to be slightly different. But, there is no need to remove the casing around the rough opening for a door replacement. If you take accurate measurements of your current, finished door opening – a reputable door manufacturer can safely cut a door that is a perfect replacement.

Don’t make the mistake of presuming the exact door size without taking measurements. You may need to make sure that the door opening is square and that you are certain of the exact size of the door replacement to fit your opening

Keep in mind that your custom forged iron door will be cut and manufactured exactly to the size you will supply to your door manufacturer, without any subtractions from the height or width. Here are simple and reliable methods you can follow to measure an exterior door for replacement.

How to Measure a Flat Top Door

Flat top, exterior doors come in many styles, but the measurements for these doors will be the same, including in-swing or out-swing doors, right-hand or left-hand hinges, wood slab, doors with segmented glass panels, double-entry doors, panel doors, and doors with side-lite panels. And the same applies to the material your flat top door is made of – wrought iron, wood, fiberglass, or steel.

When taking measurements, a necessary step is making sure your measuring tape is straight and without kinks or wrinkles for an accurate measurement.

  • Height Measurement – take a door opening height measurement from the bottom finished floor to the inner of the top trim which will be the height at the top of the door. Record this height and door frame width measurements in inches.
  • Width Measurement – With the measuring tape parallel to the floor, measure from the inner edge of the left trim surface to the inner edge of the right trim surface of the door opening.
  • Alternative Width Measurement – If you are concerned that entry is not straight or is out-of-square, take two width measurements from the lower portion of the door opening and the upper portion of the door opening – and take two height measurements on each side of center.

Use the alternative width process of measuring the door opening for older homes where the door opening or threshold may not be square. The door manufacturer may subtract up to 1/4 inch from both the height and width measurements to account for trimming.

Measuring an Arched or Round Top Door

Measuring for an arch or round top doors will require additional height measurements. Some arched doors have a geometric top shape, such as hexagonal or triangle. But most will have a radius, and these include cathedral arch, round top arch, Tudor arch, or an oval arch. The measurements and the shape description should be enough for a custom exterior door replacement. Remember to record all measurements in inches.

Height Measurement #1 – with a plumb tape measure, measure from the finished floor to where the arch starts. You don’t need to do this on both sides, because the measurement arch will be symmetrical and the height distance should be the same.

Height Measurement #2 – take an arch height measurement from the finished floor to the inner point at the top trim which will be the height at the top of the door arch.

Width Measurement – With the measuring tape parallel to the floor, measure from the inner edge of the left trim surface to the inner edge of the right trim surface of the door opening.

Helpful Tips on How to Measure a Door and Get it Right!

The first thing you want to avoid is attempting to remember your measurements. Have a paper and pencil ready to write down each measurement you take. Better yet, make a quick sketch of your door and dimension your drawing as you take measurements while standing inside the home.

The old saying, “measure twice, cut once”, is true. Take each measurement two times, and if they don’t equal, then measure again. While recording measurements, write down any concerns you may have, such as damage to the frame, loose screws, or a worn threshold.

The most common exterior door thickness is 1.75 inches, but measure the door thickness along the edge of the existing door. You can also measure the depth of your door’s opening by measuring edge-to-edge of the door’s frame (known as the jamb), as well.

You should also consider taking a picture of the door to be replaced and the front door frame. This will give your professional door installers a better idea of your home’s entry and the condition of your door’s framing system.

Jot down any important specifics to your front door replacement, such as the direction it opens, the side on which the hinges are mounted, and any special lock set you will be replacing.

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