Computation of the Check Digit

The last number of the IMEI is a check digit calculated using the Luhn algorithm.

According to the IMEI Allocation and Approval Guidelines,

The Check Digit is calculated according to Luhn formula (ISO/IEC 7812). See GSM 02.16 / 3GPP 22.016. The Check Digit shall not be transmitted to the network. The Check Digit is a function of all other digits in the IMEI. The Software Version Number (SVN) of a mobile is not included in the calculation. The purpose of the Check Digit is to help guard against the possibility of incorrect entries to the CEIR and EIR equipment. The presentation of Check Digit (CD) both electronically and in printed form on the label and packaging is very important. Logistics (using bar-code reader) and EIR/CEIR administration cannot use the CD unless it is printed outside of the packaging, and on the ME IMEI/Type Accreditation label. The check digit shall always be transmitted to the network as "0".

The check digit is validated in three steps:

1. Starting from the right, double every even-numbered digit (e.g. 7 → 14)

2. Sum the digits (e.g. 14 → 1 + 4)

3. Check if the sum is divisible by 10 Conversely, one can calculate the IMEI by choosing the check digit which would give a sum divisible by 10. For the example IMEI 49015420323751?,