Where curtains can be complicated to get right for your windows, blinds can provide an easy alternative.

[Read more: 5 ways to make your windows more private]

With so many options to choose from it can be difficult to know what to choose. Kirsty Martin from Web-Blinds explains what you need to know before buying one.

1. Know your fittings

 Blinds can either be fitted inside the window recess, or outside the window, which is called exact fitting, so start by deciding which look you prefer. In some cases, you'll only be able to do one or the other.

Remember, roller blinds take up less space when rolled up than Roman blinds, so this may be a consideration.

2. Made to fit

The advantages of recess fitting are that the blind is made to fit the window and works with its proportions, and the window sill and wall around the window can still be used.

The disadvantage is that light will flare around the edges of the blind, so you'll also need to fit curtains outside the window if you want to cut out all the light.

3. A clear view

Exact fitting can give the impression of a taller or wider window, either by fitting the blind well above the window, or choosing a blind that's wider than the window.

[Read more: 5 things you need to know about subsidence from signs to treatments]

This also leaves the window completely clear when the blind is up.

However, a blind fitted outside the recess takes up wall space and may be in the way of furniture.

4. Measure from top to bottom

For recess fitting, measure the width of the recess in three places - the top, middle and bottom. Measuring in centimetres, take the smallest measurement and round it down to ensure the blind fits inside the recess.

The length of the blind, also known as the drop, is from the top of the inside of the window to the window sill.

Again, measure this in three places and use the smallest measurement, although you can add more to the drop of a roller blind because it doesn't all have to be unfurled.

5. Outside measurements

For a blind hanging outside the window, decide how far you want it to extend to the left and right and measure between these points.

In general, we suggest leaving around 10cm above the window recess and at least 7cm on each side.

Then decide on the best place for the blind to end - on or just below the window sill often works well, but it may look better longer.