How to Measure Windows for Replacement: UK Step-by-Step Guide (with Diagrams)

Measuring your windows accurately is the first and most crucial step when planning a replacement project.

Incorrectwindow measurementscan lead to ill-fitting windows, drafts, and even additional costs. Whether you’re looking to replace a single window or planning a full-scale renovation, understandinghow to measure a windowproperly will save you time and money. In this guide, we’ll walk you through the step-by-step process to get precise measurements for your new windows.

Whether you’re working withuPVC,timber, ordouble glazed windows, this guide covers everything you need to know abouthow to measure windows for replacementin the UK.

Tools You’ll Need for Measuring Windows

Before you start, gather the necessary tools to ensure your measurements are accurate:

• Tape Measure: Preferably a metal one for greater precision.
• Notepad and Pen: To record your measurements clearly.
• Spirit Level: Ensures accuracy when checking for square.
• Step Ladder: If you need to measure windows located higher up.
• Smartphone or Camera: Optional, but useful for taking reference photos.

How to Measure a Window: The Basics

To get the correctwindow replacement measurements, it’s crucial to measure both the width and height of your window in several places. Here’s a general overview of how to get started:

1. Measure the Width

Begin by measuring the width of the window at three different points:top, middle, and bottom. This helps account for any variations or irregularities in the window frame.

• Top Width: Measure from the inside of the left frame to the inside of the right frame.
• Middle Width: Repeat this process in the middle of the frame.
• Bottom Width: Measure the width at the bottom of the window frame.

Record the smallest measurementas your final width. This ensures that your new window will fit snugly without any gaps.

2. Measure the Height

Next, measure the height of the window at three different points:left, centre, and right.

• Left Height: Measure from the top inside frame to the bottom of the windowsill.
• Centre Height: Measure the height in the middle of the frame.
• Right Height: Measure from the top to the bottom on the right side.

Again,record the smallest height measurementto ensure an accurate fit.

3. Measure the Depth (if Necessary)

For some replacement projects, especially if you’re installingdouble glazed windowsor auPVC window, you may need to measure the depth of the window frame. Use a spirit level to measure the distance from the interior to the exterior part of the window frame.

Tip: If you’re unsure whether depth measurements are needed, consult your window supplier or installer.

How to Measure Windows for Replacement in the UK: Detailed Steps

Here’s a more detailed breakdown of how to get perfectwindow measurements:

1. Check for Squareness

Before taking your final measurements, it’s essential to check if your current window opening is square. If it’s not, your new window may need to be custom-made to fit.

• Use aspirit levelto measure diagonally from the top left corner to the bottom right corner.
• Next, measure diagonally from the top right corner to the bottom left corner.
• If the two measurements are equal, your window opening is square. If they differ, note down the discrepancy, as it may affect your choice of replacement windows.

2. Measure the Width with a 10mm Deduction

When measuring the width forwindow replacement measurements, always deduct10mmfrom the smallest measurement. This allows space for the new window to be installed with an adequate sealant or caulking, ensuring a tight fit.

For example:If your smallest width measurement is 1,200mm, your final measurement should be recorded as1,190mm.

3. Measure the Height with a 10mm Deduction

Repeat the same process for the height, deducting10mmfrom the smallest height measurement.

For example:If your smallest height measurement is 1,000mm, your final measurement should be990mm.

4. Measure the Window Sill (if Applicable)

If your windows include a built-in sill, make sure to measure its width and depth separately. This will ensure your new window fits seamlessly into your existing structure.

• Measure the width of the sill from the inside frame to the outer edge.
• Measure the depth of the sill to ensure a precise fit.

5. Measure for Double Glazing

Forhow to measure windows for double glazing, the process is the same as above. However, it’s important to ensure that you’re accounting for the added thickness of double glazing panes if you’re replacing single-glazed windows. Confirm these details with your supplier to ensure compatibility.

Common Mistakes to Avoid When Measuring Windows

Even a small error in your measurements can lead to a window that doesn’t fit properly. Here are some common mistakes to avoid:

1. Only Measuring Once

Always measure each dimension at least twice to ensure accuracy. Double-check all measurements before placing your order.

2. Using the Largest Measurement

Never use the largest width or height measurement. Always use the smallest to guarantee a snug fit.

3. Forgetting to Measure the Sill

If your windows have a sill, forgetting to measure it can result in a window that doesn’t sit correctly.

4. Ignoring Squareness

If your window opening isn’t square, it’s crucial to choose a replacement window that can be adjusted to fit or consider hiring a professional installer.

How to Measure a uPVC Window

If you’re specifically measuring for auPVC window, follow the same steps outlined above. However, be aware that uPVC windows often come with more complex frame designs. Here’s what to keep in mind:

• Measure the full width and height, including any external trim or beading.
• Consider the depth of the existing uPVC frame, especially if you’re replacing it with a new style.

When to Hire a Professional

If you’re unsure abouthow to measure windows for replacement UK, or if your windows have an irregular shape, it’s best to consult a professional. A qualified installer can ensure that yourwindow replacement measurementsare precise, saving you time, money, and the hassle of dealing with misfitting windows.

Get Your Windows Measured and Replaced by Experts

Once you have your measurements, try our free window price calculator to see exactly how much your new windows will cost.

Don’t let incorrect measurements lead to costly mistakes. Our expert team can handle yourwindow measurementsand provide a seamless replacement service. Whether you’re replacinguPVC windowsor upgrading todouble glazed windows, we’ll ensure a perfect fit every time.

Harrington Windows Team

Window Specialists

Our team of window specialists brings over 25 years of experience in the industry, providing expert advice on home improvement, energy efficiency, and architectural aesthetics.

Certified Window InstallersEnergy Efficiency Experts