Measuring for Internal Doors

How do I measure up for an internal door?

Are you looking to replace your internal doors but aren’t sure what sizes you need?

Buying new internal doors is not a frequent activity for most home owners and knowing how to measure up is often questioned.  Thankfully it is more straight forward than you might think.

Here are a few tips to make sure that your measurements are correct and that you don’t end up with an ill-fitted door.

Measuring up

1. First thing to point out is DO NOT measure the existing door. You must always base your measurements on the door frame.

NB. if you are fitting new frames, we advise asking your Joiner to confirm the door sizes required. Where possible, fit frames that will accommodate standard size doors, as it will make life much easier by keeping the cost down and the need to purchase made to measure doors.

Working on the basis that you are keeping your existing frames, you will need three measurements: width, height and thickness.

2. DOOR HEIGHT: measure the inside of each vertical side of the frame. The longest length determines the height required. Remember to take the floor covering into account or you might struggle to shut the door.

3. DOOR WIDTH: take three measurements inside the door frame – at the top, middle and bottom. The widest measurement determines the width of the door.

4. DOOR THICKNESS: there are three standard thicknesses for internal doors – 35mm (most common), 40mm and 44mm (fire door option). Measure the frame rebate where the door will sit when closed.

Standard door sizes

There are quite a few standard door size options and you’ll more than likely still hear references to feet and inches – old habits die hard! Many of the measurements are based on the old UK imperial sizes that were converted during metrication in the 1960’s.  For details on the most common internal door sizes use our helpful size conversion chart.

What if my measurements do not quite match the standard sizes?

Most doors will have some leeway and can be planed at the sides, however you must be careful not to over trim and compromise the stability of the door. If you are unsure, contact the door supplier to confirm how much the doors can be trimmed.

Made to measure doors

If your door size requirements do not fit within the standard size options available, then you will need to look at a made to measure doors. This doesn’t have to cost the earth and many of JB Kind’s door designs can be ordered as a special size. Sometimes you might only need 1 or 2 special sizes – for example a pantry door or under stairs cupboard.