How To Measure for New or Replacement Doors: The Dale Joinery Guide

Measure your door correctly with Dale Joinery’s guide on how to measure new or replacement doors!

Measuring Internal Doors

Measuring an internal or external door isn’t as tricky as some might think, and our easy to follow guide is here to provide step by step instructions. Whether you’re building your own home or in need of replacement doors that make all the difference to your interior, any DIYer can perform this task.

The most important thing to remember when measuring an internal door is to take at least two sets of measurements to make sure they are correct. The last thing you would need is to have an oversized or undersized door delivered when all you want is to start the installation process.

How To Measure for New Internal Doors

When replacing existing internal doors, first, you will need to measure the door or all of the doors and make a note or schedule of each size. Most replacement doors come in standard sizes (height & width). Then you will need to choose the sizes that are most similar to your existing doors. The next step is the most important, always choose the standard size that is slightly larger than your existing door as the fitter will need to plane the door to fit correctly on site.

1.When you hang the door, you need to make sure you have extra room to adjust the door if necessary.

2.All doors fit differently. It depends on the door you want to fit, and it also depends on what kind of house you have. 

You want to avoid installing a new door for it to not fit the space properly. In addition, it’s worth noting that internal doors for newly built homes need to meet minimum height and width requirements in order to comply with UK building regulations.

What You'll Need To Measure

Tape measure.

Something to note the measurements on (this could be your phone or a piece of paper).

Measurements You Need To Take

You’ll need to take three sets of measurements for the height, the width, and the thickness. See below.

The door height:

Remember to measure inside of the frame.

Measure the left side first, then do the same with the right side.

Do not measure directly down the floor as you need to leave room for your floor. This will avoid the door potentially sticking to the bottom or scratching it when fitted.

Note down both measurements and the longest length will determine the height.


The door width:

You’ll need to take three sets of measurements for determining the door width. These are at the top, the middle and the bottom.

Again, you’ll need to measure inside the frame.

Note down the measurements for each, and the widest measurement will determine the width of the door you need.


The door thickness:

You need to use your tape measure to calculate the thickness of the frame. Go from the inside to the outside. 

It might be best to do this at least twice to measure it correctly.

There are three standard size thicknesses for doors, and these are 35mm, 40mm, and 45mm. The measurement you have taken for your door should match one of these thicknesses. If you would like to increase the thickness of your internal doors this is an easy upgrade to make. All you will need to do is move the existing door stop strips and hinge recesses to accommodate the additional thickness!

Measuring External Doors

Measuring external doors is different from measuring internal doors. Below you’ll find a step by step guide on how to measure an external door, whether it’s an entrance or back door for your property. It’s important to note that a minimum of 1 external door needs to provide a 775mm clear opening and include an accessible threshold. This is part of Building Regulations Part M.

The door width:

You need to measure the width of your external door (including the frame if this is to be replaced too) or the opening of your new front door. To do this, you need to take measurements across the top, middle and bottom of the door opening using a tape measure. It’s common in older buildings where the sizes may vary slightly. As a general rule, select the largest measurement as your final width size. This is because even if your door is slightly bigger, you can cut the door to suit. It’s a much easier option than having an external door that is too small!

The door height:

Measuring from the size of the opening, start from the left hand side of the door, and then measure the right side. Note down the measurements and if one side is slightly larger, select the larger of the two. 

The door width:

For existing door frames where you’re adding a replacement door, you need to measure the door thickness.

Open your existing door and measure the thickness of the door.

For completely new frames that are yet to be fitted, ensure you take note of the thickness of the frame that will be fitted.

Important Tips for External Door Measurements

Generally you would plan to sink your door set cill into the floor to reduce the potential for a step so a measurement of an existing door should always be taken externally (including the door frame cill).

If an existing door is hung into render you will not know the true size of the frame unless you create an inspection hole in the render or plaster.

Ordering New Doors Online

When you’re looking at purchasing a door online, note that the measurements are usually listed as height x width x thickness. At Dale Joinery, our timber doors are made bespoke and tailored to your requirements, so it takes away the stress and hassle of trying to find a new door that matches your exact measurements.

UK Standard Internal Door Sizes

There are various standard door sizes in the UK, but we’ve compiled a list of the most common sizes for you below. 

1981 x 610686 x 35mm – A great option where smaller doors are needed.

1981 x 762 x 35mm – This is the most common internal door size in England and Wales and can also be referred to as a 2’6” door.

1981 x 838 x 35mm – The most common door size for mobility/wheelchair access. This can also be referred to as a 2’9” door.

UK Standard External Door Sizes

Standard heights of an external door is 2090 mm high x 1000mm wide or 2090 x 890.

If you’re looking for a new door, whether internal or external, Dale Joinery specialises in timber front doors, bifold doors, patio doors, and more. You can explore the full range online today!

About Dale Joinery

At Dale Joinery, we pride ourselves in creating the ultimate timber window and door for you. We carefully source all parts of our frame and only use the best materials to guarantee product security, quality and longevity. If you’re interested in our sustainable timber windows and doors for your project, please get in touch or give us a call on 0800 030 2222. Download our digital brochure or request your physical brochure online for more inspiration.