Curtain Size Calculator – Find the Perfect Length and Width
Whether you are a novice or an expert at interior decoration, our curtain size calculator will help you calculate the length and width of the curtain you need to buy or sew to achieve your desired window treatment style. Choosing the correct curtain size is not as simple as it may seem at first: personal taste, room style, ceiling height, and safety all influence the final measurements.
How to Measure Your Window for Curtains
Before buying or making curtains, always measure your window accurately. The typical units used for curtains are inches (US/imperial) or centimeters (metric). Measure from the top of the window frame (or where the rod will be placed) down to the point where you want the curtain to end.
- Sill length – to the top of the window sill
- Apron length – to the bottom of the window apron (trim below the sill)
- Café / Half length – covering only the lower half of the window (great for kitchens)
- Floor length – just brushing the floor (most common for living rooms and bedrooms)
- Puddle / Extra long – pooling on the floor for a dramatic, luxurious effect
Standard Curtain Lengths
Ready-made curtains come in standard lengths. In the imperial system the most common long curtain lengths are 63, 72, 84, 96, and 108 inches. Short curtain lengths are 24 and 36 inches. In metric these correspond roughly to 160, 183, 213, 244, 274 cm (long) and 61, 91 cm (short).
Our calculator automatically recommends the nearest standard size equal to or greater than your measured length, so you always buy curtains that are long enough.
How the Curtain Length Formula Works
The calculator adds a rod height (the distance from the top of the window to where the rod is mounted) to the window height. For standard installations this is typically 4 inches (≈10 cm). For high ceilings or a more dramatic look, 6 inches (15 cm) is recommended. For puddle/extra-long curtains, an additional 6 inches (≈15 cm) of fabric is added so that the curtain pools gracefully on the floor.
- Sill / Apron / Floor: Curtain length = Window height + Rod height
- Café: Curtain length = Window height ÷ 2
- Puddle: Curtain length = Window height + Rod height + 6 in (15 cm)
How to Calculate Curtain Width
For curtains to look full and elegant rather than flat, they should be wider than the window. The standard practice is to multiply the window width by a fullness factor:
- Light fullness (1.5×) – suitable for sheer or light fabrics
- Standard fullness (2×) – recommended for most living rooms and bedrooms
- Extra fullness (2.5×) – for heavy fabrics or a very luxurious look
The calculator then divides the total width by the number of panels to give you the width per panel.
What to Do If Your Curtain Is Too Long
If the curtains you purchased are slightly too long you have several options:
- Hem them – take up the excess fabric with a simple hem.
- Puddle them – let the extra length pool on the floor intentionally.
- Adjust the rod – mount the rod higher to use up more fabric at the top.
- Add rings or clips – attaching rings can raise the effective hang point.
Pitfalls to Avoid When Choosing Curtains
- Never measure only the glass area – always measure the full window frame.
- Account for the rod position before buying; mounting the rod high elongates the room visually.
- Check fabric weight: heavy velvet needs more fullness than lightweight linen.
- For safety in children's rooms, avoid floor-length or puddle-style curtains near cords and furniture.
- Remember that curtains shrink slightly after washing – factor in 2–5 % for washable fabrics.
Frequently Asked Questions
- What is the most popular curtain length?
- 84 inches (213 cm) is the most popular ready-made length for standard 8-foot ceilings. For 9-foot ceilings, 96 inches (244 cm) is preferred.
- How much wider should curtains be than the window?
- As a rule of thumb, curtains should be 1.5–2.5 times wider than the window. For most rooms, a 2× fullness (double width) gives a full, elegant look.
- Should curtains touch the floor?
- Floor-length curtains are the most common choice and create a classic look. They should just skim the floor (within ½ inch / 1 cm) for a clean appearance, or pool 3–6 inches (8–15 cm) for a dramatic puddle effect.
- How high should I hang curtains?
- For standard windows, mount the rod 4–6 inches (10–15 cm) above the window frame. For a taller, grander look – especially in rooms with high ceilings – mount the rod as close to the ceiling as possible.
- What are café curtains?
- Café curtains cover only the lower half of the window. They provide privacy while allowing natural light in through the upper portion – popular in kitchens and bathrooms.