Depending on package weight and delivery zone, discounts can amount to as much as 71% off of most priority and standard overnight envelope packages (First Overnight Service is excluded). These envelope discounts also come with a "Bonus Weight" Program which enables you to "overstuff" envelopes to their physical holding capacity (the standard maximum weight is usually 8 ounces for overnight service).
FedEx rate calculations are based on both the weight of the package and the distance from origin to destination (for simplification FedEx classifies distance by shipping zones). You can calculate your charges by reviewing these rate tables and by requesting a Zone Chart for your specific Origin Zip Code on www.fedex.com.