How to Measure Your Doors
Getting the correct measurements is one of the most important steps when ordering new doors. Our straightforward guide explains how to measure your door's width, height and thickness, helping you choose the right size for your home.
What you'll need: A tape measure, pencil and notepad. Record all measurements in millimetres (mm).
Step 1: Measure the Width
Measure horizontally across your existing door, from one vertical edge to the other.
- Measure across the top of the door.
- Repeat across the middle.
- Measure across the bottom.
- Record all three measurements in millimetres.
Step 2: Measure the Height
Measure vertically from the top edge of the existing door to its bottom edge.
- Measure down the left-hand side.
- Repeat through the centre.
- Measure down the right-hand side.
- Record all three measurements.
Step 3: Measure the Thickness
Open your existing door and measure the thickness across its edge.
- Open the door to expose its vertical edge.
- Place your tape measure across the thickness of the door.
- Measure from one face of the door to the other.
- Record the thickness in millimetres.
Measuring an Empty Door Frame
If you don't have an existing door to measure, you'll need to measure the opening within the frame instead.
- Measure the internal width of the frame at the top, middle and bottom.
- Measure the internal height at the left, centre and right.
- Check whether the frame is square and whether the floor is level.
- Allow for the appropriate fitting clearances when determining the finished door size.
Important: The frame opening measurement is not necessarily the size of door you need to order. The correct clearances depend on the door, frame, threshold and any fire-rating requirements.
Common UK Internal Door Sizes
Internal doors are available in a range of imperial and metric sizes. The table below shows some commonly available examples.
| Door Size | Height | Width |
|---|---|---|
| 24" x 78" | 1981mm | 610mm |
| 27" x 78" | 1981mm | 686mm |
| 30" x 78" | 1981mm | 762mm |
| 33" x 78" | 1981mm | 838mm |
| Metric | 2040mm | 626mm |
| Metric | 2040mm | 726mm |
| Metric | 2040mm | 826mm |
| Metric | 2040mm | 926mm |
Please note: Not every door design is available in every size. Always check the sizes and thicknesses shown on the individual product page before ordering.
Important Checks Before Ordering
Can the Door Be Trimmed?
Some doors can be reduced in width or height to achieve the correct fit, but trimming allowances vary considerably between manufacturers and door designs. Always check the manufacturer's permitted trimming limits before purchasing or altering a door.
Are You Replacing a Fire Door?
Fire doors require particular care. The door, frame, seals, hinges and other components must be suitable for the relevant certified installation. Never assume that a fire door can be trimmed in the same way as a standard internal door. Check the manufacturer's certification and installation instructions.
Check Your Door Frame
Make sure the existing frame is in good condition, suitably sized and capable of accommodating your chosen door. Changes in door thickness may also require adjustments to the frame or door stops.
Check the Finished Floor Level
Remember to consider carpets, tiles and other flooring, particularly if new flooring will be installed before or after the door is fitted.
Measure Every Door Separately
Even doors that appear identical may have slightly different dimensions. Measure each opening individually rather than assuming every door in your home is the same size.
Need Help Choosing the Right Size?
Our experienced team is here to help with door sizes, specifications and product selection. Contact Doors of Distinction before ordering if you're unsure which size you need.
Contact Our Team