How to use this calculator
Start by measuring the width and height of your window opening in inches. Then measure the distance from the top of the window frame to the ceiling. If you have multiple windows side by side on the same wall, enter the number of windows so the calculator can determine the total span.
Choose your curtain style, desired look, mount type, and length preference. The calculator will show you the recommended rod length, the best height to mount it, where to place your brackets, and how wide and long your curtain panels should be. It also tells you which standard rod size to purchase.
Standard curtain rod sizes
Most adjustable curtain rods come in four standard sizes. Picking the right one means your rod will overlap the brackets properly and look proportional to the window.
| Rod size | Adjustable range | Best for window widths |
|---|---|---|
| Small | 28 to 48 inches | Up to 36 inches |
| Medium | 48 to 84 inches | 36 to 72 inches |
| Large | 84 to 120 inches | 72 to 108 inches |
| Extra Large | 120 to 170 inches | 108 to 156 inches |
Choosing the right curtain length
Floor length curtains are the most popular choice for living rooms and bedrooms. They should just barely touch the floor or hover about half an inch above it. Puddle length curtains add 2 to 3 extra inches of fabric that pools on the floor for a romantic, formal look.
Sill length curtains end right at the window sill and work well in kitchens or above radiators. Below sill curtains hang about 4 inches past the sill, giving a slightly more finished appearance while still keeping fabric away from heat sources and countertops.
Frequently asked questions
How long should a curtain rod be compared to the window?
A curtain rod should extend 3 to 6 inches beyond each side of the window frame for a standard look, or 8 to 12 inches beyond each side for a wider, more dramatic appearance. This extra width lets you stack the panels off the glass when they are open so you get maximum natural light.
How high should I hang my curtain rod above the window?
For the most polished look, mount the rod 4 to 6 inches above the top of the window frame, or as close to the ceiling as possible. Hanging curtains high creates the illusion of taller ceilings and makes the room feel more open and airy.
How wide should curtain panels be for fullness?
Curtain panels should have a combined width of 2 to 2.5 times the width of the window for a full, gathered look. For sheer curtains, aim for 2.5 to 3 times the width. If you are using two panels (one on each side), each panel should be about 1 to 1.25 times the window width.
How many brackets do I need for a curtain rod?
Every rod needs at least two brackets, one at each end. Add a center support bracket for rods longer than 48 inches to prevent sagging. For rods over 96 inches, use two center supports spaced evenly along the rod. Heavy fabrics may need additional supports even on shorter rods.