The exact measurement of the custom shutter window is not as difficult as you think. You need to identify the mount type 1st and then take accurate measurements from all dimensions. If you want to make your window shutter installation process stress free, your measurement should be perfect.
This guide will teach you all the key points that you need to understand for measuring window shutters.
Get the necessary tools
Make sure you have all essential tools for measuring the size of windows. The right tools will make your work easy and help you to get more accuracy without any errors. Following are the necessary tools:
- A steel measuring tape is the most important tool throughout the procedure. It provides you with the exact measurement.
- You also need a pencil and a diary to note down the recorded values. So, this can reduce the chances of any mistake.
- A step ladder is necessary to reach the higher windows. It makes the procedure safe.
- A spirit level is an optional tool but useful to check whether the window is level or aligned.
Types of shutters in term of mount type
It is necessary to understand the mount type for measuring window shutters. There are two types of mounts in custom window shutters.
Inside mount
Have you ever seen shutters and blinds fitted within the window recess? This type of window treatment is called inside mount or reveal fit shutters. You need to measure its depth and squareness with care because a small error can cause big trouble. So you need to take precise measurements to ensure the proper fitting of the shutter within the frame.
Outside mount
Outside mounts are installed directly to the wall, unlike the inside mounts. There is no recess space required as they are fixed out of the frame. They cover the entire area of the window and you will not be able to find space for the light from its sides.
Outside mounts are best for uneven and shallow window frames. It allows you a little room for flexible measurement.
How to measure inside mount of window shutters
You can measure the inside mount in three ways.

Measure the height of the inside mount
You can measure the window height from three different points, left, centre and right. All three measurements start from the top of the recess to the bottom. Note down all the measurements and use the shortest value to cover the proper window space.
Measure the width of the inside mount
Similarly, measure the width of the inside mount left to the right from three different points, the uppermost, the middle and the lowermost of the recess. Record all the values and use the shortest one to ensure precise fitting of the shutter without any hurdle.
Measure the Obstacles of the inside mount
Check the hurdles in the frame like locks and handles. If there are any, measure that obstacle with great care. Make sure you provide enough room for the shutters to operate and move freely without any hurdles.
How to measure outside mount of window shutters
You can measure width, height and Check Architraves and Sills for the outside mount shutter in three ways.
Measure the height & width
Measure the height and width from three different points, left, middle and right for height and top, centre and bottom for width.

Take all the measurements and write them down on paper separately. Use the highest value to make sure complete coverage of the window.
Now add an extra space of 2 to 3 inches from each side, as shown in the image. It offers better light control, extra beauty and smooth working to the window.
Check Architraves and Sill
Before finalising the measurement, you need to check the architraves and sills carefully. Make sure the surrounding area of the window is flat enough and ready for shutter installation.
Uneven trim and blockage in the sill can affect the smooth working of the window. If there is something out of order, then readjust the measurement to let the shutter fix properly in its space.
How to measure Corner and bay window shutters
Corner and bay windows are made of different small sections instead of a larger one. They are not flat like the normal windows. So to counter its squareness, you need to measure each section separately.
Suppose you have a large bay window made with 3 small windows. Each window needs a separate measurement as each one has its own frame.
Angled bay window
An angled bay window is a three faceted structure projected outward from the wall. It gives your room a spacious and fancy appearance.

To measure the angled bay window, you need to check how far the window is projected from the wall. After that, decide which type of shutter you want to install. Now check if the shutter has a handle or lock, and then start measurement accordingly.
Measure each section of the window from three points, left, centre and right for the height. Record all values and use the smallest (for inside mount) one to make sure proper fitting.
In the same way, measure each section for width from the top, middle and bottom. Record all values and use the smallest one.

Use angle finder tool to get the measurement of angles in angled bay windows. Make sure you have noted the exact degree of each angle separately.
If you don’t have an angle finder tool, then use the paper templates for this purpose. Place the paper template where the angle meets and move it against the window until it fits with the angles appropriately. Press the paper template slightly into the corner to get a more precise result. Fold the paper, mark with a pencil where they intersect each other. Now you can see the exact shape of the angle.

The given image shows the paper template method.
You can also use a mobile application to find angles. Applications that can be used for angle measurement are;
- Protractor + Angle Finder
- Bubble Level & Angle Gauge
- Clinometer
- Angel Meter
All these apps use mobile sensors to find exact angles.
Box bay window
As the name reveals that box bay window is like a box attached to the wall outside. Usually, it consists of 3 panels ( might be more than 3). One is the large front panel and two small side panels joined with 90° angles.
It is easy to measure a box bay window if you follow a simple rule. Consider each section of the window as a separate window.
Measure the width of the main panel from edge to edge of the wall. Next, measure the height of the main panel from three different points, left, centre and right. You can take the smallest value for perfect window fitting in the recess.
In the same way, you need to measure its side panels separately. You can start from the outer side edge of the window. Then you should move towards the inner corner. Write down each measurement separately as all these sections have different dimensions.
After that, measure each side panel for height from three points top, centre and bottom similar to the main panel. Write all the values and use the smallest one.
For the inside mount box window shutter, measure the depth of the window reveal carefully. A small reveal depth can cause a big trouble.
In the end, measure the angles with the angle finder tool, or you can use mobile applications.

Conclusion
Measuring the custom shutter windows might seem difficult for you in the beginning. But if you understand the basics, it will become much easier. The simple rule is to identify the right mount, measure from 3 points and double check all the values. A small mistake can damage the final finishing.
If you are working on standard windows, bay windows and corner windows, only 1 rule is applicable for all: measure carefully, write every detail and use the right tools. This rule can give you comfort and elevate your ambience’s beauty.
Don’t make a guess measurement, get high professionals from BC SHUTTER to make your windows a perfect and stylish shutters.
Faqs
Is it necessary to take measurements for each window separately?
Yes, you should measure each window separately as each one has different dimensions.
What should be the recess depth for inside mount shutters?
The ideal recess depth for inside mount should be 75 to 100 mm. You can also reduce the recess depth to 60 – 75mm for basic windows.
Do I need a professional to measure the windows or can I do it myself?
You can measure the windows yourself but there is a chance that you can make mistakes while measuring. So our recommendation is to hire a professional for measurement to avoid any errors.
What tools can I use for measuring windows for custom shutters?
Tools required for measuring windows are,
- Steel measuring tape
- Pencil
- Paper
- Angle finder
- A step ladder for larger windows
How do I measure the handles or locks to provide enough space for shutters to operate freely?
Measure the projection space of the lock and handles from different angles. Give some extra space for the caution so that the chances of collision are reduced.
What is the best way to read the markings in inches for accurate measurement?
One inch on a measuring tape is equal to 8 small lines. One small line is the ⅛ part of one inch. If you record the window measurement as 15 inches and 4 small lines, then your exact measurement would be 15¼, which is equal to 15.5 inches.
How can I check the squareness of the window?
You can check the squareness of the window by measuring the diagonals. Measure from the top right corner to the bottom left corner. Then measure from the top left corner to the bottom right corner of the window. Now compare both values. If they are equal, then your window is square, if not, then it is not square.
How to order custom shutters?
After you have done the measurement, select the shutter design and go to you suppliers website like BC SHUTTER. Give them details and order your customised shutters.
Can I use a mobile application to get measurement?
Yes, you can use mobile applications for taking measurements. There are different applications like,
- Bubble Level & Angle Gauge
- Clinometer
- Angel Meter
- Protractor + Angle Finder
These applications use sensors and make your work easy and more efficient.
How to avoid common mistakes while measuring windows?
You can avoid common mistakes by following the given guidelines.
- Measure multiple times
- Use right tools
- Record every value with detail and confidence
- Keep the measuring tape straight; there should be no bends.
- Double check every detail because accuracy is everything.
What are bay windows?
Bay windows are slanted, not flat. They are like a box and projected outside the wall giving extra space to the room.



