Let me tell you about the most expensive measuring mistake I've ever witnessed. A customer ordered twelve beautiful oak doors for their Victorian home renovation – £2,400 worth of premium doors. When they arrived, not a single one fit properly. The problem? They'd measured the door openings instead of the actual door sizes needed. It was a costly lesson that could have been avoided with proper measuring technique.
After four decades of fitting doors across Sheffield, Dronfield, and Chesterfield, I've seen every measuring mistake in the book. The good news? With the right approach and a bit of patience, measuring internal doors is straightforward. Let me walk you through the professional method that ensures you get it right first time.
Here's the thing about doors – they're not forgiving. Unlike curtains or carpets that can be adjusted, a door that's too big or too small is a door that doesn't work. Too big, and you're looking at expensive modifications or returns. Too small, and you'll have unsightly gaps that let through light, sound, and draughts.
I've learned that taking an extra ten minutes to measure properly can save you hours of frustration and potentially hundreds of pounds in mistakes.
Don't try to wing this with a wonky tape measure you found in the kitchen drawer. Here's what you actually need:
Pro tip: If you're measuring multiple doors, create a simple sketch of your floor plan and label each opening. Trust me, after the third door, they all start to look the same!
I know it seems obvious, but you'd be surprised how many people try to measure around an existing door. Take it off its hinges – it only takes a few minutes and gives you clear access to the frame.
This is where many people go wrong. You need to measure the frame opening, not the door itself. Here's how:
Measure at three points: left side, centre, and right side of the frame opening. Why three? Because older properties (and even some newer ones) can have frames that aren't perfectly square.
Use the smallest measurement. If your measurements are 1981mm, 1983mm, and 1980mm, use 1980mm. This ensures your door will fit through the tightest point.
Measure from the floor to the top of the frame opening – not to any architrave or decorative moulding.
Same principle applies here – three measurements at different heights:
Top, middle, and bottom of the frame opening. Again, use the smallest measurement.
Measure the actual opening between the frame sides, ignoring any stops or rebates for now.
This determines what thickness of door you need. Most internal doors are 35mm thick, but fire doors are typically 44mm. Measure from the face of the frame on one side to the face on the other side.
Every home has its quirks. Is the floor level? Are there any pipes or cables that might interfere? Is the frame square? Make notes of anything unusual – it'll save headaches later.
Most UK internal doors come in standard sizes, which makes life easier once you know what they are:
Heights: Usually 1981mm (6'6") for standard doors, though older properties might have different heights.
Widths: Common sizes are:
If your measurements don't match these standards exactly, don't panic. Most doors can be trimmed to fit, though there are limits to how much you can take off.
I've heard it countless times: "It's only 2mm out, that'll be fine." No, it won't. 2mm might not sound like much, but it's the difference between a door that fits perfectly and one that binds or has unsightly gaps.
Are you planning to change the flooring? That new thick carpet or laminate will affect your door clearance. Always consider the finished floor height, not just what's there now.
Your old door might have been trimmed, adjusted, or might never have fitted properly in the first place. Always measure the frame opening, not the existing door.
Use your spirit level to check if the frame is square. If it's significantly out of square, you might need professional help to get a proper fit.
These need extra clearance for the folding mechanism. Check the manufacturer's specifications, but typically you'll need about 20mm less width than your opening measurement.
The track system needs to be considered in your measurements. Again, check the specific requirements for your chosen system.
These are typically thicker (44mm vs 35mm) and have specific clearance requirements. The gaps around fire doors are regulated, so precision is crucial.
Sometimes, measuring reveals problems that need professional attention:
Don't see this as failure – it's smart planning. Better to identify issues early than struggle with a door that never quite works properly.
Before you place your order, measure everything twice. I know it sounds tedious, but I've seen too many expensive mistakes to recommend anything else. Take your measurements, have a cup of tea, then go back and measure again.
If you're ordering multiple doors, create a clear list with room names and measurements. "Front bedroom door: 762mm x 1981mm x 35mm" is much clearer than "Door 3: 762 x 1981 x 35".
Here in Sheffield, we believe in doing things properly. That means taking the time to measure accurately, double-checking everything, and not cutting corners. Your doors are going to be opened and closed thousands of times over their lifetime – they deserve to fit perfectly from day one.
Whether you're renovating a Victorian terrace in Dronfield or updating a modern home in Chesterfield, accurate measuring is the foundation of a successful door installation. Take your time, be methodical, and don't be afraid to ask for help if you're unsure.
Remember, a door that fits perfectly isn't just about function – it's about pride in your home. Every time you walk through a properly fitted door, you'll know you got it right.
