Your curtains are a major decorative feature of your home. It is not uncommon in Britain to have at least one wall in each room completely filled by the window. This means that at least one side of the room will be dominated during the hours of darkness by the curtains you choose. During the day, your curtains will frame you view of the garden, or hide your view of the street. How you hang your curtains is up to you, but you should know the basic rules of curtain installation.
The width of the curtain pole is an important factor in the overall width of your curtains. No matter how you choose to hang your curtains, they should at least stretch to the width of the window. Some homes have windows that fit right up to a side wall of a room, leaving almost no room for the curtain rail to exceed the width of the window. In these cases you just have to take the rod right up to the side wall. If space is not a factor, then you should allow the curtain rod to extend 15 to 30 cm (6 to 12 inches) beyond the side of the window. If you have finials on the end of the rod their width is on top of the 15 to 30 cm rule.
The purpose of making the curtain rod wider than the curtain is that you need to be able to clear the space of the widow when you open the curtains. The curtains in their open state should overlay the wall either side of the window and should only over lap the window by about 4 or 5 cm (1.5 to 2 inches). This is not a hard and fast rule, however. If you have a very wide window you should extend the curtain rod a little further. The curtains will be very tightly gathered when they are open and so you do not need the same width on the wall as the window to display the curtains in their open state.
You may not like having such wide windows. In this case, you can reduce the visual effects of the windows by overlapping the location of the open curtains with the window. Thus break the rule about extending the curtain rod if your design demands different priorities. However, don’t cut off the rod exactly above the edge of the window. This would result in light coming in at the side of the curtain. Curtains stand away from the wall and you will have an open gap if there is not enough extra curtain at either side of the window to trap light. If you do not intend to open the curtains at the top, but wish to draw them to the sides and tie them back, you should go a lot wider with your curtain rod and fix your ties directly below the finials of the rod.
The standard rule for curtain width is that they should be twice the width of the window. However, there are circumstances where you could go down to one and a half time the width and others where you should bulk up to two and a half times the width. Influencing factors include the type of material. If you have thin material you can give them a stronger presence by increasing the gather and this will require a wider length. If you fix your curtains by sliding large holes (called eyelets) in the top of them over the curtain pole instead of using hooks, you will need more width. If your window directly abuts a side wall on one side you should reduce the width of your curtains down to the one and a half times window width rule. Ultimately, it is your decision, but don’t go lower than one and a half time the width of the window in any circumstances.