Curtain Calculator
Show the math
What Your Result Means
- Fabric width: The total curtain width needed after applying your chosen fullness multiplier. Standard fullness (2×) means twice your window width for a pleated, gathered look.
- Cut length: Your window height plus 8 inches to allow for a header pocket and bottom hem. Adjust if your hardware or style needs differ.
- Panels: The number of 54-inch-wide fabric panels needed. Fabric bolts are typically 54" wide, so wider windows require multiple panels sewn together.
- Total yards: The linear yardage to purchase from the fabric store. Consider adding 10–15% extra for pattern matching or cutting waste.
How This Calculator Works
You enter each window's width and height in inches, the number of windows, and a fullness ratio. The tool multiplies window width by the fullness factor to get the gathered fabric width, adds 8 inches to the height for hem and header allowances, then divides by a standard 54-inch bolt width to determine how many panels you need. Total yardage is panels times cut length, converted from inches to yards.
Quick Questions
What fullness ratio should I choose?
Standard (2×) works for most fabrics and gives a classic gathered look. Use 1.5× for flat or casual panels, and 2.5× for sheer or lightweight fabrics where you want extra volume and opacity.
Does this account for pattern repeats?
No. If your fabric has a repeating pattern, you will need extra yardage to align motifs across panels. Ask your fabric store for the repeat length and add one repeat per panel as a starting estimate.
Why is the panel width fixed at 54 inches?
Most home-décor fabric bolts are 54 inches wide. If your fabric is a different width (such as 45" or 60"), adjust the mental math accordingly — this calculator assumes the 54" standard.
Should I add extra fabric?
Yes. A 10–15% overage is typical to cover cutting errors, shrinkage after washing, and slight measurement differences. For patterned fabric, add one full pattern repeat per panel.
What does the 8-inch allowance cover?
It provides roughly 4 inches for a rod-pocket or header at the top and 4 inches for a double-fold bottom hem. If you plan pinch pleats or a different hemming style, your allowance may vary.
Sources
- University of Georgia Extension — Measuring and Estimating Fabric for Window Treatments (fullness ratios and yardage formulas)
- Wikipedia — Curtain (standard panel widths and construction overview)
Method & review
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.