Can you feel a breeze through the gaps in your windows? Does your current set look old and outdated? Or is it time for a modern upgrade? The first step before installation is measuring. Learning how to measure for replacement windows is necessary. As the old adage goes, measure twice, cut once. Measure incorrectly, and you’ll face costly consequences.

This guide will prepare you and equip you with everything that you’ll need to measure for replacement windows. It’ll ensure that your brand-new windows fit as snugly as a glove and will save you from delays and additional costs. Plus, you’ll have the added benefit of windows that last longer and are running at maximum energy efficiency.

Whether you are a DIY enthusiast or a seasoned pro, this guide will have you covered. We’ll share the equipment that you’ll need, the measurements required, and precisely how to take them.

Tools Required for Measuring

You’re going to need some specific tools to get the job done properly. Before you even begin to think about measuring, make sure that you gather these up. The good news is that there’s only a small handful required, and you’ll most likely own them all already. Tape Measure: Any tape measure will do, but a sturdy, retractable metal one will be best. The added rigidity will help when measuring harder to reach sections. Spirit Level: Spirit levels easily show when you’re measuring straight. They also ensure that you’re not accidentally measuring a lump on the surface. If you’re working in an older property, this will be an important part of your kit. Many smartphones have levels built into them, but they’re not recommended due to software inaccuracies. Pencil and Notepad: You have to record your measurements somewhere! This is the best option, as you can quickly scribble them down without needing to grab other equipment.

This isn’t a lengthy list of tools, but each is vital if you want to finish the job with an accurate set of measurements.

How to Measure for Replacement Windows: Step-by-Step

Now that you’ve gathered up your tools, it’s time to start the measuring process. We’ve broken it down into manageable steps for you to follow. Take your time and make sure that you’re being accurate at every stage of the process.

Measure The Width

Measuring the width of the window requires 3 measurements. The top, the middle, and the bottom. It might be tempting to take a quick measurement in one spot, but you risk ordering windows the wrong size should there be any warping.

Place the end of the tape measure on one side and pull it across to the other side. Make sure that it’s level.

Record each measurement and keep the smallest one. This will ensure that if there has been warping or some unevenness, the new windows will fit into the gap.

Measure The Height

As with the width, take the two edges and the middle, then measure from top to bottom.

Record all three measurements, but keep the smallest one. This ensures that your new windows will easily fit into the smallest part of the opening.

Measure The Depth

Measuring the depth is a bit trickier. You need to open the window and try to measure from the outside of the window to the inside stop.

Measure from multiple points and make sure that you don’t include any obstructions and additional fittings.

Check For Square

The square measurement checks if a window is square (orderly in a rectangle shape) or is out of square.

To check if your windows are square, measure from one corner diagonally to the other. Then repeat across the other diagonal.

If the measurements are the same (or very similar), then the window is square. If there are big differences, then the window is not square, and you'll need professional help.

Measuring Tips

Whenever you take a measurement, write it down and then label it. It’s amazing how quickly you can forget a number. It’s important that you also measure at least twice. This will cut down on inaccuracies from a wandering tape measure.

When to Seek Professional Help

Taking measurements of your own windows at home is rewarding. It’s all part of a larger project, so of course, you’d like to be part of it. There are, however, certain times when seeking professional help is necessary. Complicated Window Shapes: Arches, circles, triangles, and any other shape that isn’t a rectangle or square makes for an awkward time measuring. Professionals know how to do this efficiently and accurately. Visible Structural Issues: If you notice that there are issues with the windows around the frames or the wall that they are built into, it’s time to call professionals. They can recommend remedial works that may affect the size of the windows that you can install. Historic Homes: Historic homes tend to come with unusual windows and awkward shapes. There may be some restrictions on how you can alter the exterior of the home. Check with a professional for further information. Large Projects: Sometimes, you simply can’t measure a window using a tape measure. Large windows, skylights, and floor-to-ceiling projects will require professional assistance.

Window Replacement Measurements

Understanding how to measure for replacement windows is the first step in bringing elegance and comfort to your home. If you have one takeaway from this guide, make sure that you measure twice. It’s surprising just how often you’ll find the measurements change…

The sturdier the tape measure, the better. Avoid using a flexible fabric tape measure if possible.

Always write down your measurements.

If you’re ever in doubt, be sure to ask for professional assistance.

Debating DIY vs. professional window replacement? Why not have a chat with us here at, All County Exteriors? We offer replacement windows, doors, and commercial projects throughout New Jersey and surrounding areas. It’s easy to schedule a consultation.