Measuring Windows 
for
Buying Curtains

Measuring windows when wanting to buy curtains is done to make sure that the correct length and width is bought.

When buying ready made curtains they will come in a pack of two curtains (one pair) that will fit one window.

The pack will state the length and width of one curtain in that pack and come in preset finished width sizes usually 117 cm (46 inch), 168 cm (66 inches) or 228 cm (90 inches) and a preset finished length or drop of the curtains usually 137 cm (54 inches), 183 cm (72 inches) or 228 cm (90 inches).

There are many different types of tracks or poles that suit many different types of windows. Some different shapes of windows may need some extra calculations such as bay windows which will use much more material than straight forward flat windows.

The window in the above picture measures 111 cm (43.5 inches) in height, shown by the white arrow, and 123 cm (48.5 inches) in width, shown by the black arrow.

Now that the window has been measured, the next step is to determine where the curtains are going to be placed and with what type of pole or track is going to be used.

Are the curtains going to be placed inside the window recess? This would possible be the case for thin net curtains using tension rods or possibly a blind. The width of the rod would be the width of the window.

If they are to cover the whole window once closed then a curtain track or pole needs to be fixed in between the window and the ceiling, usually placed 10 cm (4 inches) above the window. The track will need to extend beyond the window edges by about 15 cm (6 inches) each side.

When the tracks or poles are fixed in place that would increase the height of the window and in turn the length of the curtain.

There are so many decisions to make when buying curtains but in order that the curtains fit once they have been hung on the track or poles, these steps need to be considered.

The next step is where the curtain will sit. Either on the window sill or below the window sill.

When placing curtains to sit on the window sill care needs to be taken with any ornaments being also placed there. When the curtains are pulled open the hem may knock anything on the sill.

Usually the amount above and below the sill could match 10 cm above and below the window.

Get the right curtain length by measuring windows

For the window shown the curtain size needed is 168 x 137 cm and the working out is as follows, 

window height in cm = 111.

additional height       =  20 (This is the extra 10 cm top and bottom of the window)

Total height or length = 130 cm.

Window width in cm = 123

additional width       =   30  ( This is the extra 15 cm either side of the window)

Total Width = 153 cm.

The curtain needed for this window would be Width 153 cm and length or drop 130 cm.

In inches the width would be 48.5 + 12 = 60.5

In inches the length or drop would be 43.5 + 8 = 51.5

The size of the bought curtains would be width 168 cm (66 inches) by drop 137 cm (54 inches).

The curtain size that is needed for the window and the reset finished sizes do not match up accurately so choose the nearest size to the required one.

The packs have two (or a pair) of curtains inside them so each curtain will be this size and when the heading has been pulled into pleats or the eyelet curtains put onto the poles one curtain will just cover half the window. Because each curtain is one window width they should drape well.

Measuring Windows for a Bay Window

When looking from the outside a bay window looks like it is stuck onto the wall as it protrudes out from the rest of the wall. Inside the house The wall recess is there for either a flat window or a bay.

A bay extends the floorspace of a room by varying depths. The depth of the bay in the picture above is 84 cm (33 inches) some other may have a larger or smaller footprint,

The process of measuring the window is very similar to flat windows but with a bay there is a choice whether to go into the bay with the curtains this brings the bay part into the room or keep the curtains on the inside wall and have the bay floorspace behind the curtain.

Measuring for Bay Window Curtains

Using the white arrows for guidance and if going into the bay, measure from the centre point of the front window to the bay corner, then from the bay corner to the start of the inside wall, then along the inside wall for about 15 cm (6 inches) as before. That is half the width so it needs to be doubled.

Calculation for width

Middle to corner = 86 cm (34 inches)

Corner to wall edge = 100 cm (40 inches)

Front Wall Overlap  = 15 cm (6 inches)

Total Width (cm) = 86 +100 +15 = 201 x 2 = 402 cm

Total Width (inches) = 34 + 40 + 6 = 80 x 2 = 160 inches

Required Drop 178 cm (70 inches)

Curtain size required is two packs of width 228 cm (90 inches) and drop 183 cm (70 inches)

Using the black arrow for guidance, measure across the top and down to the floor as before.

For this window the width at the top is 315 cm (124 inches) and the drop is 213 cm (84 inches)

Curtain size required is two packs of width 168 cm (66 inches) and drop 228 cm (90 inches).

The two calculations differ as one is wider and shorter than the other one. The two packs can be left separate or the two edges slip stitched together to make one big curtain.

Hope this helps in measuring windows for curtains.