How to Measure for Internal Doors
Getting the measurements right is one of the most important parts of ordering your new internal door. Follow this guide before entering your required width and height on the product page.
If you're replacing an existing door, measure both the current door and the frame opening. Older frames are not always perfectly square, so don't rely on a single measurement.
Measurements are the customer's responsibility. This guide is intended to help you take basic starting measurements. Final trimming, fitting gaps and clearances can vary depending on the frame, floor level, hinges and door type.
Width
Measure across the opening at the top, middle and bottom. Use the smallest measurement as your guide.
Height
Measure from the top of the opening down towards the finished floor in at least two places. Again, use the smallest measurement.
Measuring your internal door
Take your time and write each measurement down clearly before moving on.
Measure the width
Measure the existing door or the inside of the frame opening at the top, middle and bottom. Use the smallest measurement as your guide, as frames are not always perfectly square.
Measure the height
Measure from the top of the opening down towards the floor in at least two places. Use the smallest measurement, especially if the floor is uneven or if carpet, laminate or thresholds may affect the fit.
Check the door thickness
If you are replacing an existing internal door, measure its thickness too. Many internal doors are around 35mm thick, but always check the specification of the door you are ordering.
Check the frame condition
Look at whether the frame is square, damaged, twisted or out of level. If the frame is not straight, the door may require additional trimming or fitting by a joiner.
Check floor clearance
Consider carpet, underlay, laminate, tiles and thresholds. These can all affect the clearance required underneath the finished door.
Measure everything again
Take every measurement more than once and write it down clearly. If your measurements are close to a standard size, or you are unsure what size to order, ask us before placing your order.
A few final checks
A door isn't fitted in isolation. Flooring, frames, hinges and the condition of the opening can all affect the final size required.
Finished floor level
Make sure your measurement allows for any flooring that is still to be installed, including carpet, underlay, laminate or tiles.
Existing frame
Check that the frame is suitable to reuse and look for distortion, damage or uneven gaps before ordering.
Door swing
Think about which way the door needs to open and where the hinges and handle will sit once fitted.
Trimming and fitting
Trimming allowances vary between products. Check the individual door specification before making assumptions about how much can be removed.
Enter your required size on the product page
Once you're happy with your measurements, choose the internal door you want and enter your required width and height into the size fields on the product page.
Available sizes can vary between door designs, so always use the permitted measurement range shown on the individual product.
View Internal DoorsDon't guess. Speak to us before placing your order or check your measurements with the person who will be fitting the door.
Ask Us for AdviceThings to avoid when measuring
A few simple checks can help prevent problems when your new door arrives.
Only measuring once
Openings can vary from top to bottom. Check several positions rather than assuming the frame is perfectly square.
Ignoring the finished floor
New flooring can change the available height and the clearance required underneath the door.
Assuming every door can be heavily trimmed
Trimming allowances differ between door constructions. Always check the individual product specification first.
Guessing fitting allowances
The finished door size may require fitting allowances depending on the opening. If you're not confident working this out, ask your fitter or speak to us first.
Internal door measuring FAQs
Answers to some of the most common questions before ordering an internal door.
Should I measure the door or the frame opening?
What if my frame isn't square?
Do I need to allow for carpet or flooring?
Are all internal doors 35mm thick?
How many times should I measure the opening?
What should I do if I'm unsure which size to order?
Help before you order
If you're unsure about your measurements, door size or suitability, speak to our team before placing your order.
