STEP #1 - Measure Your Windows - SEE GUIDELINE  BELOW

When measuring for horizontal blinds the first thing to do is to make sure you start with the right kind of measuring instrument. It’s best to use a metal tape measure, but a yard stick will also work. Avoid using cloth tape measures, or measuring with a string, because cloth tapes and string stretch, which can cause the measurement to be inaccurate. The second step is to decide if you want to mount the blinds on the inside of the window, known as an inside mount, or to the outside of the window, which is known as an outside mount. If you decide to mount the blinds to the outside of the window, keep in mind that the blinds will end up covering the casing, or be mounted on the casing. If you decide to mount the blinds on the inside of the window make sure you measure the depth of the casing or else the blind slats will stick out past the edge of the window. Depending on the depth of the window frame blinds can still be inside mounted even if the window depth will not allow a full recessed mount. In this case a protruding inside mount can be provided.  Now that you have the tools you need, and have decided on a type of mounting you can begin to measure your window. To measure for an inside mount make sure to measure the depth of the casing first because horizontal blinds will not always fit the depth of a window. If you want to have one inch slats, you will need at least a depth of one and a half inches. If you want two inch slats, you will need a depth of at least two and a half inches. The next step for measuring for an inside mount is to measure the width. Most people make the mistake of only measuring the width at the top of their window, but windows are not always built square. For a more accurate measurement, three measurements need to be taken. All three measurements will be measured from the inside of one side of the window, to the inside of the other side of the window. The first will be done at the top, the next will be at the middle and the last will be at the bottom of the window. Once you have those three measurements, it is time to measure the length. The length is measured in a very similar way. It requires three measurements all from the inside of the top of the window, to the inside of the bottom of the window. The three measurements of length should be taken from the right, left and middle of the window. Once you have your length and widths measured, take the smallest width and the longest length and you have your measurement for an inside mount. To measure for an outside mount, you only need to take two measurements: the width and the length. Measure from one side of the outside of the casing to the other side of the outside of the casing. To measure the length, measure from the top of the outside of the casing to the bottom of the window. Once you have those two measurements, it is recommend that you add three inches to each side of the width, so that the blinds will clear the casing.