Dell service tag format is either 7 or 5 characters. Dell Express Service Code format is either 8/10/11 digits. Both service tags and express service codes are directly related. Given one type, the other can be computed.
Dell's service tag numbers are alpha-numeric sequences used as serial numbers for the equipment they sell. They are helpful when getting support, but must be converted to numerical sequences called Express Service Codes when using Dell's automated phone help. This allows purchasers to more easily key them in on a standard touch-tone pad.
Dell computers include a little converter program that allows users to convert alpha-numeric "service tags" into number-only "Express Service Codes" when dialing in to the support line.
Service Tag is a base-36 integer (composed of digits [0-9A-Z]). Once you have the Service Tag, you can calculate express service code yourself. Express Service Code is base-10 decimal integer of Service Tag. Dell uses express service code mainly for their support call-routing. When you call dell support, their automated call-routing system may ask you to enter express service code, which you can easily enter in your telephone, as it is just a bunch of numbers, instead of characters.
Use the following online tools to find express service code from service tag and vice-versa.