How to measure for a new (or replacement) door

Measuring a front door or internal door for replacement is pretty easy. Measuring a door opening without a frame is a little more complicated, but still relatively straightforward.

The rule to remember is, always err on the bigger side because you can sand down, but you can’t add it back on.

If your door is too small or loose it could rattle in the frame and will have gusty draughts around the edge. Taking time to get the perfect fit makes a big difference in energy efficiency.

To hang a wooden door, a skilled joiner is needed to ensure the door sits straight in the frame.

For composite or uPVC doors, these usually come as a complete doorset built with the frame for a perfect fit with the door and frame.

Measuring for a doorset is the same as measuring for a door opening without a frame below.

It’s always better to use a reputable installer that will take responsibility for the measurements. At Everest, we take all measurements for our doorsets and guarantee a perfect fit for your door without any rattling draughts.

Do you measure a door from the inside or outside?

When measuring the door, you can measure from the interior or the exterior as they are both the same.

There are three ways to measure a door:

• Measure the existing door (if it fits well in the frame)
• Measure inside the door frame
• Measure the door opening brick to brick

Measuring doors is a little different from windows because you can measure the actual existing door if you have it. Whereas you should never measure an existing window frame.

Take your measurements in metric millimetres and use a metal tape measure.

Measure the door width

• Start by measuring the width inside the door frame from door jamb to door jamb.
• Make sure you hold the tape measure taut and that you are measuring across in a straight line.
• Measure at the top and bottom, and in the middle.
• Compare the measurements and use the biggest measure.

Measure the door height

• Next measure the height of the door inside the frame. Start from where the floor level is going to be or the existing sill up to the underside of the door frame lintel.
• Measure the left side and then the right side.
• It is possible, the measurements could be different for each side if the door or frame isn’t straight.
• Take the biggest measurement and use that for the door height. Once the door is fitted it will be planed and sanded to fit.

Measuring a door opening without a frame

If you have an opening without a frame, or if you are measuring for a new doorset you need to measure the full opening where the door and frame will sit.

To get the correct measurement, the tape measure must be set against the edge of the brick opening and measured to the opposite brick across the opening. Brick to brick in a straight line.

Once you have that measurement you will need to factor in how wide the door frame will be and deduct that from your measurements.

Speak to your manufacturer to get guidance on the required depth for the frame.

As mentioned at the beginning, when measuring a door, it’s always better to go slightly over size rather than under, so you have the tolerance to sand the door down.

Consider your floor covering

If you are fitting a door before a new floor covering has been added, allow for the new floor height. That could be more or less than what you have already.

Make sure to factor the differences for a new floor into measurements before you buy your new door.