An RV awning purchase consists of two separate purchases:  the roller and fabric section and the arm set.  
If you have an existing awning or if one was previously installed on your RV, you will need the following measurements to select the correct awning or for us to advise you on a replacement:

Width: Measure from the center of one arm over to the center of the other arm (or between the previous bracket locations.) This measurement will be generally on the even foot, although we can get custom off-foot lengths made.

Height: Awning arms come in different heights to fit different heights of vehicles. It is imporant to get the correct arms so that you have the maximum slope for drainage while not having the roller too low to the ground when extended. Measure from the top bracket down to the bottom bracket.  The awning arms should be selected to be in a matching height range to the measurement.

If this is a new installation:
  1. Find a location near the bottom of the side wall on which you are installing the awning to attach the bottom brackets.  This should be at a level where there is a solid stud, floor joist, etc. behind the wall to anchor the bottom brackets into.
  2. Identify the location along the roofline with a solid backing to mount the top brackets.  There should be enough space above this location to install a 1"-2" awning rail to hold the fabric to the side of the RV.  The retracted awning roller will sit at the level of the brackets
  3. Identify two locations on the wall where there is unobstructed vertical space (no windows, appliances, cargo doors, etc.) that are an even number of feet apart (14 ft., 15 ft., 16 ft., etc.) 
  4. Once you have planned the location of the four brackets, take your measurement as described above.

Tip: If you have a new installation or if your awning rail is damaged, remember to order the awning rail separately from the roller/fabric and the arms.  It is not included in the purchase of either of those awning components.

Here is a visualization of the various dimensions: