Curtain Size Calculator
Calculate curtain fabric size for your windows
Table of Contents
How to Use
- Measure your window width in inches
- Measure your window height in inches
- Select desired fullness ratio (how gathered you want the curtains)
- Enter header and hem allowances
- Click calculate to see fabric dimensions needed
How to Measure Your Windows
Accurate measurements are crucial for well-fitting curtains. Follow these steps for best results:
- Measure the width of your window frame or the curtain rod
- For width, measure from where you want the curtain to start to where it should end
- For height, measure from the top of the rod to where you want the curtain to end
- Add extra width if you want curtains to extend beyond the window frame
- Measure to the floor for floor-length curtains, or to the sill for shorter styles
- Always measure in multiple places and use the largest measurement
- Write down all measurements before calculating
Understanding Fullness Ratio
Fullness ratio determines how gathered or pleated your curtains will appear when closed:
| Ratio | Appearance | Best For |
|---|---|---|
| 1.5x | Minimal gathering | Sheer curtains, casual look |
| 2x | Standard fullness | Most curtain styles (recommended) |
| 2.5x | Full, luxurious look | Formal rooms, heavy fabrics |
| 3x | Very full, elegant | Luxury drapes, formal settings |
A 2x fullness ratio means the fabric width is twice the window width, creating a pleasing gathered appearance when the curtains are closed.
Header and Hem Allowances
Allowances are extra fabric added for finishing:
- Header allowance: Extra fabric at the top for rod pockets, tabs, or pleats (typically 4 inches)
- Hem allowance: Extra fabric at the bottom for a double-folded hem (typically 8 inches for a 4-inch double hem)
- These allowances ensure professional-looking finished curtains
- Adjust based on your specific curtain style and hanging method
- More formal curtains may require larger allowances
Fabric Selection Tips
- Consider the room's purpose when selecting fabric weight
- Heavier fabrics provide better light blocking and insulation
- Lighter fabrics allow more light and create an airy feel
- Account for pattern repeats when calculating fabric needs
- Pre-wash fabric if you plan to wash the finished curtains
- Buy extra fabric (10-15%) to account for shrinkage and mistakes
- Consider lining for better drape, light control, and longevity
Frequently Asked Questions
- What is the standard fullness ratio for curtains?
- The standard fullness ratio is 2x, meaning the fabric width is twice the window width. This creates a nice gathered look when closed while still being economical with fabric.
- How much extra length should I add for hems?
- Standard hem allowance is 8 inches, which creates a 4-inch double hem. This provides a professional finish and weight at the bottom of the curtain.
- Should I measure the window or the curtain rod?
- Measure based on where your curtain rod is or will be installed. The width should span the rod, and height should measure from the rod to your desired endpoint (floor or sill).
- Do I need to add extra width beyond the window frame?
- Yes, it's recommended to extend the rod 4-6 inches beyond each side of the window frame. This allows curtains to stack off the glass when open, maximizing light and making windows appear larger.
- How do I calculate fabric for patterned curtains?
- For patterned fabric, you'll need to account for pattern repeats. Add one full pattern repeat to your calculated length to ensure patterns align properly across panels.
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