Curtain Panel Calculator
Enter your window width, desired drop length, panel width and fullness style to find out how many curtain panels to buy, the total fabric width you need, the fabric yardage (including hem and header allowances), and an optional material cost estimate. Switch between inches and centimetres - all results update instantly.
How to measure your window for curtains
Start at the rod or track, not the window frame. Measure the full width of the curtain rod from end to end - most designers hang rods 4 to 6 inches beyond the frame on each side so open curtains stack off the glass and do not block light. For drop length, measure from the top of the rod to where you want the hem to fall: floor length usually means stopping half an inch above the floor, sill length means stopping at the sill, and cafe length means stopping halfway down the window. Write both measurements down in inches or centimetres before opening the calculator.
What is fullness and why does it matter?
Fullness describes how much extra fabric width you buy relative to the rod width. A 1x panel would lie flat with no gather at all; a 2x panel has twice as much fabric as the rod is wide, so it folds into gentle waves when drawn closed; a 3x panel is very heavily gathered. The right fullness depends on your fabric and your panel style. Grommets and tab tops look best at 1.5x to 2x because higher fullness creates a large stack of fabric that extends far into the room when the curtains are open. Pleated headers need at least 2x to form their folds cleanly. Sheers often require 2.5x to 3x because the fabric is transparent and needs extra density for privacy and a lush look.
Hem and header allowances by panel type
Ready-made curtains come fully hemmed, but if you are sewing from fabric you need to add extra length. The bottom hem typically takes 6 to 8.5 inches depending on style: rod-pocket headers need about 4 additional inches for the casing plus seam allowance; tab-top headers need about 6 inches for the loops and seam; grommets and pleated panels usually need 4 inches at the top. This calculator adds the correct allowances for your chosen style automatically so you know the exact cut length before you buy. Always add a further 10 to 15 percent for patterned fabrics that require pattern matching across panels.
Calculating fabric yardage for sewing your own curtains
If you are making curtains from a bolt of fabric, you need to know how many widths of the bolt fit across each panel and then multiply by the cut length. Standard drapery fabric is 54 inches wide. If a finished panel is 54 inches wide, one bolt-width covers it; if the panel is wider you need to seam two widths together. The formula is: (number of panels x widths per panel x cut length) / 36 = total yards. The calculator does this arithmetic for you once you enter the bolt width and the price-per-yard field gives you a ballpark cost before you visit the fabric store.
Fullness guide by curtain style
| Panel style | Light | Standard | Full | Notes |
|---|---|---|---|---|
| Rod pocket | 1.5x | 2x | 2.5x | Best at 2x for medium-weight fabrics |
| Grommet / eyelet | 1.5x | 1.75x | 2x | Higher fullness creates unwanted stack bulk |
| Pleated / pinch pleat | 2x | 2.5x | 3x | Needs more fabric to form pleats cleanly |
| Tab top | 1.5x | 2x | 2.5x | Similar to rod pocket; softer fold |
| Sheer or voile | 2x | 2.5x | 3x | Extra fullness compensates for transparency |
Typical fullness multiplier ranges recommended by interior designers for each panel style.
Frequently asked questions
How many curtain panels do I need for a standard window?
Most standard windows 36 to 60 inches wide need two panels - one for each side. Buy two panels with a total finished width of at least 1.5 to 2 times the rod width. For example, a 48-inch rod at 2x fullness needs 96 inches of fabric; two 54-inch panels give you 108 inches, which rounds up comfortably. Very wide windows or bay windows may need three or four panels.
What fullness ratio should I choose?
For most opaque curtains on a standard rod or grommet, 2x fullness is the default choice and will look well-proportioned in most rooms. Use 1.5x if you want a more minimal, tailored look - common in contemporary interiors. Use 2.5x to 3x for sheer or voile panels that need density for privacy, or for formal drapes where a truly luxurious drape is the goal. Pinch-pleat panels need at least 2x to allow the pleats to form correctly.
Do I measure the rod or the window frame?
Always measure the rod, not the frame. The rod is usually mounted 4 to 6 inches outside the window on each side so that the open curtains clear the glass and let in maximum light. If you measure only the frame you will end up with curtains that block part of the window even when pulled open.
How do I calculate the cut length if I am sewing curtains?
Start with the finished drop length you want, then add allowances. For rod-pocket curtains add about 8.5 inches at the bottom plus 4 inches for the casing at the top - giving 12.5 inches of extra fabric. For grommet or pleated panels add 6 inches at the bottom and 4 at the top (10 inches total). For tab-top panels add 6 inches at the bottom and 6 at the top (12 inches total). The calculator applies these values automatically.
Should I buy extra fabric for pattern matching?
Yes. If your fabric has a repeat pattern - meaning a motif that recurs every few inches - you need to buy extra so the pattern lines up across panels. A good rule of thumb is to add one full repeat length per panel. Divide the repeat length in inches by 36 and multiply by the number of panels to find the extra yardage. Many designers simply add 10 to 15 percent as a buffer when the repeat is short.
What is the difference between panel width and rod width?
Panel width is the finished width of a single curtain panel as sold in the package (commonly 40, 48, 54 or 72 inches). Rod width is the full length of your curtain rod from one end to the other. You need the total fabric width (rod width x fullness) to equal or exceed the sum of your panel widths. For instance, a 60-inch rod at 2x fullness needs 120 inches total; two 54-inch panels give 108 inches - slightly under. Three panels at 162 inches total give plenty of fullness.
Can I use this calculator for track curtains?
Yes. Enter the total track length as the rod width and the calculation works identically. Track systems that overlap in the centre typically add 2 to 4 inches of overlap; you can account for that by adding it to the rod width input.