I need to find out exactly what size belt I need for the blades. I think the one I have is too far gone to get an accurate measurement. Can anybody help me out with that?

Do you know your model number? That's how you find the belt that fits your blower.

Sure we can help, as soon as you get us a model number and the corrected name of your blower. BTW belts stretch very little and you normally can adjust the tension.