Window Treatment Calculator
Calculate perfect measurements for blinds, shades, and window treatments. Get sizing for both inside and outside mount installations.
Common Window Sizes
Window Measurements
Window 1
Width & Height: For inside mount, measure the exact window opening. For outside mount, measure the area you want to cover.
Frame Depth: Measure from the front of the window frame to the glass.
Treatment Type & Pricing
Mini blinds, wood blinds, faux wood
Choosing the Right Window Treatment Mount
The mount type you choose affects both the appearance and functionality of your window treatments. Inside mount creates a clean, built-in look that showcases your window trim, while outside mount maximizes light control and can make windows appear larger and more prominent.
Your window frame depth is the deciding factor for inside mount—most treatments need at least 2-3 inches of depth to operate properly. Shallow frames, casement windows, or windows with obstructions typically require outside mounting for the best results.
Window Treatment Types and Mounting Requirements
Horizontal Blinds (Mini Blinds, Wood Blinds)
Inside Mount
- Minimum 1.5" depth required
- Order exact window opening width
- Measure at narrowest point
- Clean, architectural appearance
Outside Mount
- Add 3-4" to each side for overlap
- Better light control and privacy
- Covers window frame completely
- Makes windows appear larger
Vertical Blinds
Inside Mount
- Need 2.5" minimum depth
- Ideal for sliding glass doors
- Exact opening measurements
- Neat, integrated look
Outside Mount
- Add 4-6" width for stack-back room
- Better for wide windows/doors
- Maximum light control
- Covers entire opening plus frame
Cellular Shades & Roller Shades
Inside Mount
- Minimum 1" depth for most styles
- Cordless options need more depth
- Smooth, modern appearance
- Energy efficiency benefits
Outside Mount
- Add 2-3" on each side minimum
- Better insulation properties
- Eliminates light gaps
- Works with any window depth
Roman Shades & Pleated Shades
Inside Mount
- 2-3" depth typically required
- Fabric may interfere with window operation
- Elegant, custom appearance
- Shows window trim details
Outside Mount
- Recommended for most installations
- Add 3-4" beyond frame each side
- Better proportions for fabric styles
- Eliminates gaps for better privacy
Measuring Best Practices and Common Mistakes
Critical Measuring Tips
- Measure three times: Width at top, middle, and bottom—use the narrowest measurement for inside mount
- Use a steel measuring tape: Cloth tapes can stretch and give inaccurate measurements
- Measure to the nearest 1/8 inch: Precision matters for proper fit and operation
- Check for square: Many windows aren't perfectly square, especially in older homes
- Account for trim: Decorative trim can interfere with blind operation
Common Measuring Mistakes
- Not checking depth: Assuming there's enough room for inside mount
- Measuring the glass only: Forgetting to account for frame or desired overlap
- Ignoring obstructions: Window cranks, locks, or trim that interfere with operation
- Single measurement: Not measuring multiple points to catch irregularities
- Wrong mount type: Choosing inside mount when outside would work better
Special Considerations
- Motorized treatments: Often require additional depth and electrical considerations
- Bay windows: Each section needs individual measurement and special hardware
- Arched windows: May need custom shapes or combination treatments
- Double-hung windows: Check that bottom rail can clear the sill when raised
- Casement windows: Usually require outside mount due to crank operation
Frequently Asked Questions
Should I choose inside or outside mount for my window treatments?
Inside mount provides a clean, built-in look and is ideal for windows with deep frames (at least 2.5 inches). Outside mount maximizes light control and works for shallow frames or to make windows appear larger.
How much wider should blinds be than the window for outside mount?
For outside mount, extend blinds 3-4 inches beyond the window frame on each side and 2-4 inches above and below. This maximizes light control and privacy while making windows appear larger.
What are the minimum depth requirements for inside mount blinds?
Most blinds require at least 1.5-2 inches of depth for inside mount installation. Motorized blinds and thick materials may need 3+ inches. Always measure your window frame depth before ordering.
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