A Band Saw Blades width is measured from the tips of the teeth of the blade, to the back of the edge of the blade.
If your band saw does have not have specifications set out, or available for you to refer to, then these basic guidelines should be followed when figuring out what band saw blade width you should use.
Blade width is measured from the tips of the teeth to the back edge of the blade as shown above.
The instructions for the particular machine being used should help you when selecting blade width.
Cut-Off Sawing:
If you are going to be doing Cut-Off sawing, then the blade should be as wide as the machine allows, because the wider the band saw blade is, the more straight the cut will end up being.
Also, it will allow for faster feeding which is always nice.
Contour Sawing:
If you will be doing Countour Sawing with your band saw blades, then the blade should be as wide as it can be.
It should however, still be narrow enough so that you have enough control over it so you can get the exact shape/radius you need.