How Do I Measure for a New Door or Window Before Buying Online?
If you are planning to buy a new door or window online, getting the size right is essential. Unlike a showroom where someone might visit your home, online suppliers work from the measurements you provide. Ordering the wrong size can mean extra costs, delays, or products that simply won’t fit.
At Home Build Doors, we supply made-to-measure aluminium, composite, and uPVC doors and windows. Here’s our step-by-step guide on how to measure before you order online.
How Do I Measure for a Replacement Door?
When measuring for a replacement door, don’t just measure the leaf (the part that swings open). You need to measure the full frame or opening.
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Measure the width of the opening in three places: top, middle, and bottom.
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Measure the height in three places: left, centre, and right.
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Record all measurements in millimetres and use the smallest figure for both width and height.
If you are replacing both the door and the frame, measure the structural opening—that’s brick-to-brick or stud-to-stud.
What Size Door Do I Need for My Opening?
A common search is “what size door do I need for my opening?” The answer depends on the exact measurements of your home.
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Measure the full structural opening.
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Deduct about 10mm from both the width and height.
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This gives you the manufacturing size for your new door, allowing a small tolerance for fitting.
Can You Order Custom-Size Windows and Doors Online?
Yes. Most of the doors and windows we sell are fully made to order, meaning you can provide the exact measurements and we will build to size. This is especially important if your property doesn’t fit standard UK door sizes.
Ordering made-to-measure doors and windows online ensures the product arrives ready to fit without major on-site adjustments.
Do Doors Come with Frames When Bought Online?
Another common question is “do new doors come with frames included?”
Yes. All external doors ordered online from Home Build Doors include a frame. This ensures the door and frame are perfectly matched for security, weatherproofing, and performance.
How Much Tolerance Should I Allow When Measuring for a Door or Window?
When you measure your opening before ordering online, always give us the tight opening size (brick-to-brick or stud-to-stud). Installers will then allow for tolerance.
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Standard tolerance is around 10mm in both width and height.
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This fitting gap is packed and sealed during installation to ensure a secure, insulated finish.
Final Thoughts
If you are buying a new door or window online, the key is accuracy. Always measure the structural opening in millimetres, take several measurements across the width and height, and provide the smallest figures. Allowing a small tolerance ensures your new system will fit perfectly once installed.
At Home Build Doors, we specialise in made-to-measure aluminium, composite, and uPVC doors and windows. When you order online, you can be confident your product is built to your exact requirements.
Call us today on 0333 090 7528 to confirm your measurements, or browse our full range of replacement doors and windows.
Frequently Asked Questions
What tools do I need to measure a door or window before ordering online?
A tape measure, spirit level, and notepad are all you need. Always measure in millimetres for accuracy.
Should I measure the old door or the opening?
Always measure the opening (frame or brickwork), not just the old door leaf. If replacing both door and frame, measure the full structural opening.
Can I measure myself, or should I get a professional?
Many customers measure their own openings before ordering online. If you are unsure, a surveyor or installer can confirm your figures before you place your order.