How to Measure a Window: A General Guide

Welcome to our guide on how to measure a window. This article aims to help those who are planning to renovate or replace their windows to properly measure the size of their new windows. Measuring a window may seem like a simple task, but it requires precision and accuracy to ensure the perfect fit.

Steps to measure a window

Step 1: Determine the type of window

Before measuring, it is crucial to determine what kind of window needs to be measured. Are you measuring a single or double-hung window? Is it a sliding window or a casement window? Each type of window has a different measurement process, so it’s essential to be aware of the window type.

Step 2: Measure the width

To measure the width of the window, take the measurement from the inside of the window jamb on the left side to the inside jamb on the right side. It is advisable not to take the measurement from the window trim or casing as it may lead to incorrect measurements.

Step 3: Measure the height

Measure the height of the window from the bottom of the sill to the top of the window frame. Ensure that you measure from the highest point of the sill if there is a slope.

Step 4: Find the depth

Measuring the depth of the window is essential for determining the size of the frame. Measure the distance between the interior and exterior trim to determine the depth of the window.

Step 5: Measure the diagonal

Measure the diagonal distance between the top left and bottom right corners and then top right and bottom left corners. The two measurements should be the same if the window is a square. If the measurements differ, take the mean measurement.

Step 6: Identify the frame material

Identifying the frame material is essential as it may affect the measurement process. Window frames can be made from different materials such as vinyl, wood, aluminium, or fibreglass.

Step 7: Consider the window function

If the window is intended to be operational, ensure that you leave enough measurements for the opening mechanism. Consider the window type and the size of the opening before taking measurements.

Step 8: Check the level

Ensure that the window is levelled before taking measurements. Measure the distance from the bottom left corner to the top right corner and bottom right to top left. The measurements should be the same if the window is levelled.

Step 9: Double-check the measurements

Double-check all the measurements to ensure that they are correct. Remember, even small errors in measurements can influence the window’s fit.

Step 10: Account for allowances

When measuring for replacement windows, it is crucial to account for allowances, such as the gap between the new frame and the existing frame.

Step 11: Take a photo

Taking a photo of the window can be helpful when consulting with a window specialist or when ordering custom windows. A picture can give the specialist a visual representation of the window to provide accurate advice.

Step 12: Consult a professional

If you are unsure about the measurements or want to have a professional do the job, you can book a consultation with a window specialist or installer to guarantee accurate measurements.

Tips and tricks

Tip 1: Invest in quality measuring tools

Investing in quality measuring tools can significantly improve the accuracy of measurements. Tape measures and laser measuring devices can provide more precise measurements than traditional rulers or yardsticks.

Tip 2: Measure twice

Double-checking measurements can avoid costly mistakes and ensure a perfect fit.

Tip 3: Measure when the weather is favourable

Measuring during rainy or windy weather can be challenging and lead to inaccurate measurements. Plan to measure when the weather is calm and favourable.

Tip 4: Consider energy efficiency

When replacing windows, consider the energy efficiency of the new windows to maximise the savings on heating and cooling.

Tip 5: Consult with a window specialist

Consulting with a window specialist or installer can provide information on window materials, energy efficiency, and installation.

Tip 6: Keep a record of measurements

Keeping records of measurements can be helpful when ordering custom windows, ensuring accuracy and consistency.

Tip 7: Don’t cut corners

Avoid cutting corners during the measuring process, as it can lead to errors and unnecessary expenses.

Tip 8: Measure multiple times

If you are unsure about the measurements, measure multiple times to ensure that the measurements are consistent.

Tip 9: Consider the resale value

Replacing windows can improve a home’s resale value, so consider the aesthetic appeal and energy efficiency of the new windows.

Tip 10: Allow for ventilation

Consider the amount of ventilation the window provides before taking measurements. Proper ventilation can improve indoor air quality and reduce the risk of mould growth.

In conclusion, measuring a window may seem like a daunting task, but it is crucial for ensuring the perfect fit. Take the time to measure correctly and accurately, and consider consulting with a window specialist for custom windows or professional installation. Remember to account for allowances and energy efficiency during replacement, and keep a record of measurements for future reference. With these tips and tricks, you’ll be on your way to measuring windows like a pro!

Advantages and Disadvantages of How to Measure a Window


1. Accurate measurement: By measuring a window correctly, you can ensure that the replacement window will fit snugly without any gaps.

2. Less waste: Measuring a window allows you to know the exact size of the window needed, reducing the likelihood of ordering the wrong size and having to return and replace it.

3. Cost-effective: Measuring a window helps you avoid mistakes which can lead to additional costs like buying extra materials and losing time.

4. More choices: By measuring a window accurately, you can explore a wider range of window styles and materials.

5. DIY friendly: Measuring a window is a straightforward task and doesn’t require any special skills or equipment.

6. Flexibility: Measuring a window allows you to choose whether to replace the entire window or just the glass pane.

7. Better functionality: Measuring a window ensures that the replacement window will function properly, preventing issues like air leakage and water damage.

8. Energy efficiency: Accurately sizing a window helps you choose a window that is energy-efficient, which can lower energy bills and reduce carbon emissions.

9. Helps plan project timelines: Measuring a window allows you to know how long the replacement process will take and helps you plan accordingly.

10. Increases safety: Properly measuring a window ensures that it fits securely and minimizes the chances of accidents like breakage or injury.


1. Difficulty: Measuring a window can be difficult if the window is an unusual shape or size.

2. Human error: Measuring a window manually can lead to human error which can result in incorrect measurements.

3. Time-consuming: Measuring a window takes time to ensure that everything is done correctly.

4. Requires tools: While measuring a window may not require any special skills, it does require some tools like a tape measure and level.

5. Limited perspective: Measuring a window from inside the house may not take into account the window’s exterior features, like trim or shutters.

6. Weather-dependent: Measuring a window can be weather-dependent, which can delay the project timeline.

7. May require professional help: Unusual sizing or difficult-to-reach windows may require professional help to measure correctly.

8. Cost: If you require professional assistance to measure a window, that service comes with an additional cost.

9. Inaccuracy from measurements can lead to ordering a wrong sized window or having to enlist professional help to fix mistakes, adding extra time and cost to the project.

10. Liability: If you aren’t adept at measuring a window, the liability for any errors fall on you, and out-of-pocket expenses to fix mistakes can cost more than hiring a professional.


1. Why is it important to measure a window before buying a curtain?

It is important to measure a window before buying a curtain to ensure that the curtain fits perfectly and looks aesthetically pleasing. Buying the wrong size can result in a curtain that is too short, too long, or too narrow, which can make your window appear awkward or unattractive.

2. What tools do I need to measure a window?

Measuring tape is enough to measure a window. However, if you do not have any, you may use a ruler or any other measuring tool.

3. What are the standard sizes for windows?

The standard sizes of windows can vary depending on the location and age of the building. However, the most common standard sizes are 36 x 36 inches for double-hung windows, 24 x 36 inches for sliding windows, and 30 x 36 inches for basement windows.

4. How do I measure the width of a window?

Measure the width of the window from one side to the other, including the window frame.

5. How do I measure the height of a window?

Measure the height of the window from the top of the window frame to the bottom, or to the sill if the window has one.

6. How do I measure the depth of a window?

Measure the depth of the window by measuring the distance from the front of the window frame to the back.

7. Do I measure the inside or outside of the window frame?

You should measure the inside of the window frame, where the curtain will be hung. Measuring the outside of the frame can result in an ill-fitting curtain.

8. How much material do I need for a curtain?

To determine how much material you need for a curtain, multiply the width of the window by 2 to 2.5 times. As for the length, measure from the curtain rod to where you want the curtain to end. Add several extra inches to the length to account for hems and fabric shrinkage.

9. Should I measure all windows in a room before buying curtains?

Yes, it is recommended that you measure all windows in a room before buying curtains. Windows in the same room can vary in size, and buying curtains that are the same size for all windows can result in unevenness appearance.

10. How do I measure bay windows?

To measure bay windows, measure the width of the window at its widest point, including the frame. Then measure the height of the window from the bottom to the top of the curved part.

11. How do I measure arched windows?

To measure arched windows, measure the width of the rectangle that fits within the arch of the window. Then measure the height from the highest point of the arch to the base of the window.

12. Can I use the same curtains for different windows in different rooms?

Yes, there are no rules against using the same curtains for different windows in different rooms. However, the size should be appropriate for the window to look good.

13. What if I am not confident in measuring my windows?

If you are not confident in measuring your windows, consider hiring a professional or visiting the store where you will purchase your curtains. These people are trained to take accurate measurements and will be able to help you choose the appropriate size for your window.

How to Measure a Window

Measuring a window sounds like a simple task, but it can be more complicated than you might imagine. Without the exact measurements, you’ll end up with improperly fitting window treatments that won’t do their job and won’t look good either. That’s why it’s essential to measure your windows carefully to ensure that you get the best results. Here’s how to measure a window step-by-step.

Conclusion and Closing

Measuring your windows takes no time at all, but it has a significant impact on your home and your comfort. A well-fitted window makes the room look better and more polished, and it also provides insulation from the outside world. Whether you’re updating your home’s decor or trying to keep the heat out, it’s important to put some time and effort into measuring your windows. With this guide, you’ll get it right every time!

Thank you for reading our guide on how to measure a window. We hope it was informative and helpful. If you’ve enjoyed this article, don’t hesitate to share it with your friends and family. For more tips and tricks on home improvement, check out our other articles. Until next time, happy measuring!