Curtain Size Calculator
This curtain size calculator works out the exact curtain dimensions for your windows so panels never look skimpy or come up short. Enter your window width and height, pick a hanging style and fullness, and it returns the ideal rod width, the cut size for each panel, and the total fabric you need.
It covers both sides of the question: how wide and how long your curtains should be, and how much fabric to buy or sew. Whether you are choosing ready-made panels, sewing custom drapes, or fitting out a whole room, the results update instantly as you change any input.
How to Use
Measure your window
Enter the Width and Height of your window in the Window Measurements section. Use the unit switch at the top to work in cm or inches — existing values convert automatically when you flip it.
Choose your options
Set the Mount Type (Inside or Outside), the Hanging Style, the Fullness, the Curtain Length, and how many Panels you want. Choosing Floor or Puddle length reveals a Sill to Floor field for an accurate drop.
Fine-tune (optional)
Open Advanced Options to adjust the rod extension per side, how far the rod sits above the window, the bottom and side hems, and the pattern repeat for patterned fabric.
Read your results
See the recommended rod width, the cut width and length per panel, and the total fabric needed. A Calculation Breakdown lists every value used so you can check the maths.
Features
Rod Width Recommendation
Calculates the ideal rod width from your window size and rod extension, so the curtains clear the glass when open.
Cut Size Per Panel
Gives the cut width and cut length for each panel, with side hems, header, and bottom hem already added in.
Total Fabric Needed
Adds up the fabric area across all panels and reports it in square metres or square feet depending on your unit.
Inside & Outside Mount
Choose an Inside Mount that fits the frame or an Outside Mount that extends beyond it for a wider, more dramatic look.
Five Hanging Styles
Grommet, Rod Pocket, Pinch Pleat, Tab Top, and Back Tab — each applies its own header allowance automatically.
Four Fullness Levels
Pick 1.5× Flat, 2× Standard, 2.5× Full, or 3× Sheer to control how gathered and luxurious the panels look.
Four Length Styles
End the curtains at the Sill, Below Sill, Floor, or with a Puddle effect, using a sill-to-floor measurement where it matters.
2 or 4 Panels
Split the fabric into 2 panels (one per side) or 4 panels (two per side) for wider windows and patio doors.
cm & Inch Units
Switch between centimetres and inches with one click; inputs convert and results display in your chosen unit.
Advanced Customization
Tune rod extension, rod height above the window, bottom hem, side hem, and pattern repeat for patterned fabric.
Pattern Repeat Matching
Enter the repeat distance and the cut length rounds up so motifs line up across every panel.
Detailed Breakdown
A clear summary lists window size, mount, style, fullness, length, and every allowance used in the result.
Frequently Asked Questions
How wide should curtains be compared to the window?
Curtains should be wider than the rod so they look full and can close completely. This calculator multiplies the rod width by your chosen fullness — typically 2× — and splits that total across your panels, so each panel ends up far wider than half the window. Choosing an Outside Mount also lets the rod extend past the frame for extra coverage.
How do I measure for curtains?
Measure the width and height of your window opening and enter them in the Window Measurements section. If you want floor-length or puddle curtains, also measure straight down from the window sill to the floor and enter that as the Sill to Floor distance. Take floor measurements at a few points, since floors are not always level.
What fullness ratio should I use (1.5×, 2×, 2.5×)?
For most curtains, 2× fullness gives a classic gathered look. Use 1.5× for a flatter, more modern style, 2.5× for a richer, fuller appearance, and 3× for sheer or lightweight fabrics that need extra gathering to flow well.
What is the difference between inside and outside mount?
Inside mount installs the rod within the window frame for a clean, fitted look. Outside mount places the rod above and beyond the frame, making the window appear larger and improving light control. When you pick Outside Mount, the calculator suggests a default rod extension and rod height above the window, which you can refine in Advanced Options.
How much fabric do I need to make curtains?
The Total Fabric result is the full area across all panels, including fullness, side hems, the header allowance for your hanging style, and the bottom hem. It is shown in square metres when you work in cm and in square feet when you work in inches, so you can match it to how fabric is sold near you.
What is pattern repeat and when should I use it?
Pattern repeat is the vertical distance between identical points in a repeating fabric design. For patterned fabric such as stripes, florals, or geometrics, enter the repeat distance and the calculator rounds each panel's cut length up to a whole number of repeats so the pattern aligns across panels. For solid fabric, leave it at 0.
Should I choose 2 or 4 panels?
For standard windows, 2 panels (one per side) is typical. For wider windows or patio doors, 4 panels (two per side) gives better coverage and a more balanced look. The total fabric amount stays the same either way — it is simply divided into more, narrower panels.
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