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Blinds Size Calculator
Estimate blind width and blind height for inside or outside mount using window measurements and optional allowances.
Enter your dimensions
Current unit: feet. The estimate updates automatically in your browser.
Choose inside mount for the measured opening size, or outside mount to add overlap allowances.
Enter the measured window or opening width.
Enter the measured window or opening height.
Optional. For outside mount, this is added on both left and right sides.
Optional. For outside mount, this is added above the window opening.
Optional. For outside mount, this is added below the window opening.
Estimated result
Blind width
Enter your inputs
Your estimate will appear here automatically once the required inputs are valid.
Guide
How to use this estimate
How the blinds size calculator works
This calculator estimates blind width and height from the measured window opening and the selected mount type. Inside mount returns the measured opening size. Outside mount adds side, top, and bottom allowances for overlap.
Inside mount returns the measured opening size. This calculator does not apply automatic manufacturer deductions. Always follow the supplier’s measuring guide before ordering.
What to measure
Measure the window or opening width and height. In imperial mode, enter measurements in inches. In metric mode, enter measurements in centimeters.
For outside mount, enter the side allowance, top allowance, and bottom allowance you want to add. For inside mount, the calculator does not add these allowances.
Example blinds size calculation
- Mount type: outside mount
- Window width: 60 inches
- Window height: 72 inches
- Side allowance: 3 inches
- Top allowance: 3 inches
- Bottom allowance: 3 inches
- Blind width: 60 + (2 × 3) = 66 inches
- Blind height: 72 + 3 + 3 = 78 inches
Estimated outside-mount blind size: 66 inches wide and 78 inches high.
Quick reference
| Item | Value | Note |
|---|---|---|
| Inside mount | window width × window height | Returns measured opening size without automatic deductions. |
| Outside width | window width + 2 × side allowance | Adds overlap on both left and right sides. |
| Outside height | window height + top allowance + bottom allowance | Adds overlap above and below the window opening. |
Common mistakes to avoid
- Assuming inside mount automatically includes manufacturer deductions.
- Adding side allowance only once instead of on both sides for outside mount.
- Using outside-mount allowances for an inside-mount blind.
Frequently asked questions
Does inside mount include a deduction?
No. Inside mount returns the measured opening size. This calculator does not apply automatic manufacturer deductions. Always follow the supplier’s measuring guide before ordering.
When should I use outside mount?
Use outside mount when the blind will sit outside the window opening or when you want extra overlap for coverage, privacy, or light control.
Should I enter allowances for inside mount?
You can leave allowances blank for inside mount. The inside-mount formula returns the measured window opening size and does not add side, top, or bottom allowances.