Blind Size Calculator
Calculate Your Blind Dimensions
Enter your window measurements to find the correct blind size for inside or outside mounting.
What is a Blind Size Calculator?
A Blind Size Calculator is a tool designed to help homeowners, DIY enthusiasts, and installers determine the correct dimensions for window blinds before ordering. It takes your window measurements and the type of mount (inside or outside) to provide the precise width and height the blinds should be ordered at. Using a Blind Size Calculator minimizes errors that can lead to ill-fitting blinds, saving time and money.
Anyone planning to install new window blinds or shades should use a Blind Size Calculator. It’s particularly useful for custom-made blinds where accuracy is crucial. Common misconceptions include thinking window sizes are standard (they vary greatly) or that you order the exact window size for inside mounts (deductions are needed).
Blind Size Calculator Formula and Mathematical Explanation
The calculations performed by the Blind Size Calculator depend on whether you choose an inside mount or an outside mount.
Inside Mount:
- Blind Order Width = Window Width – Width Deduction
- Blind Order Height = Window Height (or sometimes with a small deduction, but usually ordered at exact height for inside mount)
The width deduction is crucial for inside mounts to allow the blind to operate freely within the frame without scraping the sides. This deduction is often factory-made based on the blind type, but our Blind Size Calculator allows you to input a typical value.
Outside Mount:
- Blind Order Width = Window Width + (2 * Overlap Width per side) + any extra for frame coverage
- Blind Order Height = Window Height + Overlap Height (usually above the frame for hardware and below for light control)
For outside mounts, you add to the window dimensions to ensure adequate coverage and light blocking.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Window Width | Measured width of the window opening | inches/cm | 12 – 120 inches |
| Window Height | Measured height of the window opening | inches/cm | 12 – 120 inches |
| Mount Type | Installation method (Inside or Outside frame) | N/A | Inside, Outside |
| Width Deduction | Amount subtracted from window width for inside mount | inches/cm | 0.25 – 0.5 inches |
| Overlap Width | Extra width added per side for outside mount | inches/cm | 1 – 3 inches |
| Overlap Height | Extra height added for outside mount (total) | inches/cm | 1 – 4 inches |
Variables used in the Blind Size Calculator.
Practical Examples (Real-World Use Cases)
Example 1: Inside Mount for a Bedroom Window
You have a bedroom window that measures 35 1/2 inches wide and 47 3/4 inches high inside the frame. You want an inside mount roller shade, and the manufacturer suggests a 1/4 inch width deduction.
- Window Width: 35.5 inches
- Window Height: 47.75 inches
- Mount Type: Inside
- Deduction Width: 0.25 inches
Using the Blind Size Calculator:
Blind Order Width = 35.5 – 0.25 = 35.25 inches
Blind Order Height = 47.75 inches
You would order blinds at 35 1/4″ W x 47 3/4″ H.
Example 2: Outside Mount for a Living Room Window
You want to cover a living room window that is 70 inches wide and 60 inches high. You want to use an outside mount to make the window appear larger and block more light, with 2 inches of overlap on each side and 3 inches above the frame.
- Window Width: 70 inches
- Window Height: 60 inches
- Mount Type: Outside
- Overlap Width per side: 2 inches
- Overlap Height (total): 3 inches (e.g., 3 above, 0 below)
Using the Blind Size Calculator:
Blind Order Width = 70 + (2 * 2) = 74 inches
Blind Order Height = 60 + 3 = 63 inches
You would order blinds at 74″ W x 63″ H.
How to Use This Blind Size Calculator
- Measure Your Window: Carefully measure the width and height of your window opening. For inside mount, measure inside the frame at three points (top, middle, bottom for width; left, middle, right for height) and use the smallest width and longest height. For outside mount, measure the area you want to cover.
- Enter Dimensions: Input the window width and height into the “Window Width” and “Window Height” fields of the Blind Size Calculator.
- Select Mount Type: Choose “Inside” or “Outside” mount.
- Enter Deductions/Overlaps: If inside mount, enter the recommended width deduction. If outside mount, enter the desired overlap per side and total extra height.
- Calculate: The Blind Size Calculator automatically updates the “Blind Order Dimensions” and other details as you type or when you click “Calculate”.
- Read Results: The primary result shows the width and height you should use when ordering your blinds. Intermediate values explain the calculation.
Always double-check your measurements before ordering. Refer to the blind manufacturer’s specific instructions for deductions, as they can vary based on the blind type and hardware.
Key Factors That Affect Blind Size Calculator Results
- Window Frame Squareness: If your window frame isn’t perfectly square, inside mount measurements need to use the narrowest width and longest height to ensure the blind fits and covers.
- Mount Type: This is the most significant factor. Inside mounts require deductions, while outside mounts require additions (overlaps).
- Blind Type: Different blinds (roller, Venetian, Roman, vertical) have different headrail sizes and hardware, which can influence the necessary deductions or minimum mounting depth for inside mounts. Check our guide to types of blinds.
- Manufacturer Specifications: Always check the manufacturer’s guidelines for the specific blinds you are ordering. They will provide the exact deductions needed for inside mounts.
- Obstructions: For inside mounts, check for window cranks, handles, or alarm sensors that might interfere with the blind’s operation. This might necessitate a smaller deduction or an outside mount. For outside mounts, ensure there is enough flat surface above and around the frame.
- Desired Light Control/Privacy: For outside mounts, larger overlaps provide better light blocking and privacy.
Frequently Asked Questions (FAQ)
- What is the difference between inside and outside mount?
- Inside mount fits within the window frame for a clean look, while outside mount is installed on the wall or trim above and around the window, covering a larger area. Our window measurement tips guide has more.
- How much should I deduct for an inside mount?
- Deductions vary, but 1/4 to 1/2 inch total width deduction is common. Always check the blind manufacturer’s specifications as it depends on the product.
- How much should I add for an outside mount?
- Add at least 1.5-3 inches to the width on each side and 2-3 inches to the height (mostly above the frame) for good coverage and light control with an outside mount.
- What if my window isn’t perfectly square?
- For inside mount, use the narrowest width and longest height measurement to ensure the blind fits within the smallest part and covers the longest part.
- Can I use this Blind Size Calculator for all types of blinds?
- Yes, this Blind Size Calculator gives you the order dimensions based on standard principles. However, for specific deductions or minimum depths for inside mounts, refer to the manufacturer of your chosen custom blinds, whether roller shades or Venetian blinds.
- Where do I measure for inside mount?
- Measure inside the window frame where the blind will sit. Take width measurements at the top, middle, and bottom, and height at left, middle, and right.
- Where do I measure for outside mount?
- Measure the area you want the blind to cover, usually the outer edges of the window trim or wider if desired. Add extra for overlaps.
- What is minimum mounting depth?
- For inside mount, it’s the depth of the window frame required to install the blind’s headrail fully recessed or flush. It varies by blind type.
Related Tools and Internal Resources
- Types of Blinds: Explore different styles like Venetian, roller, Roman, and vertical blinds.
- How to Install Blinds: Our step-by-step DIY guide for installing your new blinds.
- Window Measurement Tips: Detailed guide on accurately measuring windows for various treatments.
- Custom Blinds: Browse our selection of made-to-measure window blinds.
- Roller Shades Calculator: Specific tool if you are looking at roller shades.
- Venetian Blinds Guide: Learn about the features of Venetian blinds.