Spaces and dashes are ignored. 14 digits computes the check digit, 15 digits validates it, 16 digits is read as an IMEISV and the last two are treated as the software version.
Privacy: this calculator is plain JavaScript running on your own device. Nothing you type is sent to Aikon or to anyone else, nothing is logged, and nothing is stored. Once the page has loaded you can disconnect from the network and it still works.
What does an IMEI calculator do?
An IMEI calculator does arithmetic on the digits you give it. It computes the fifteenth digit, the check digit, from the first fourteen, and tells you whether the last digit of a complete IMEI matches the value the formula produces. It is not a lookup service: there is no database behind it, and there does not need to be, because the check digit is fully determined by the digits in front of it.
An IMEI is 15 digits in three parts: the first 8 are the TAC, the Type Allocation Code the GSMA assigns to a brand owner for a model, the next 6 are a serial number chosen by the TAC holder, and the fifteenth is the check digit. The GSMA publishes the allocation rules and the registry behind them in its IMEI Database overview, and the number format itself is specified in 3GPP TS 23.003, published by ETSI. What the calculator above accepts depends on how many digits you paste.
| Digits entered | What it is | What the calculator returns |
|---|---|---|
| 14 | IMEI base: TAC plus serial, no check digit | The check digit and the complete 15-digit IMEI |
| 15 | Complete IMEI | Valid or invalid, plus the digit the formula expects |
| 16 | IMEISV: base plus a 2-digit software version | The software version, the 14-digit base, and the check digit for it |
How is the IMEI check digit calculated? (Luhn algorithm)
The check digit comes from the Luhn formula, the same checksum used on payment card numbers under ISO/IEC 7812-1. Take the first 14 digits. Starting from the second digit, double every second one. Subtract 9 from any doubled value greater than 9. Add the resulting values together. The check digit is whatever you must add to that total to reach the next multiple of ten. Worked through for the base 35316105214284, the doubling falls on positions 2, 4, 6, 8, 10, 12 and 14:
| Position | Digit | Action | Value added | Running sum |
|---|---|---|---|---|
| 1 | 3 | keep | 3 | 3 |
| 2 | 5 | double to 10, subtract 9 | 1 | 4 |
| 3 | 3 | keep | 3 | 7 |
| 4 | 1 | double | 2 | 9 |
| 5 | 6 | keep | 6 | 15 |
| 6 | 1 | double | 2 | 17 |
| 7 | 0 | keep | 0 | 17 |
| 8 | 5 | double to 10, subtract 9 | 1 | 18 |
| 9 | 2 | keep | 2 | 20 |
| 10 | 1 | double | 2 | 22 |
| 11 | 4 | keep | 4 | 26 |
| 12 | 2 | double | 4 | 30 |
| 13 | 8 | keep | 8 | 38 |
| 14 | 4 | double to 8 | 8 | 46 |
| Total | 46 | |||
The sum is 46, the next multiple of ten is 50, and 50 minus 46 is 4. The check digit is 4 and the complete IMEI is 353161052142844. Validating a 15-digit IMEI is the same operation across all 15 digits: if the total is a multiple of ten, the check digit is correct. Change any single digit and it stops being a multiple of ten, which is what the checksum is designed to catch. The calculator prints this table for whatever you enter. The longer walkthrough lives in how an IMEI is built.
What is the difference between an IMEI calculator and an IMEI checker?
A calculator answers a question about the number. A checker answers a question about the device. The calculator on this page works out or verifies the check digit and splits the number into TAC, serial and check digit. It never queries anything, so it can tell you that a number is arithmetically well formed, and nothing more.
A checker looks the device up. Blacklist status, carrier lock, activation lock and financed-device status live in databases held by the GSMA, by carriers and by manufacturers, and reading them requires paid access or an authorised account. The GSMA IMEI Database is the industry reference for allocation and for reported devices. On this site, IMEI Check is the single-number format and Luhn check with links to the right source for each next step, and GSMA Status explains what each status word in a returned report means. Use the calculator when you are building or repairing a number, and a checker when you want to know something about the handset.
Why does a wholesale buyer need a check-digit calculator?
Because manifests arrive imperfect, and the check digit is the cheapest way to separate a clerical problem from a real one before anyone spends money on paid lookups.
Three patterns account for most of it. The first is transcription: a digit typed twice, two swapped, a number read off a worn label. The second is spreadsheet damage, where a long run of digits is stored as a floating point value and rendered as 3.56938E+14, so the trailing digits are gone before the file reaches you. Asking for the column as text, or for a CSV rather than an XLSX, fixes that at source. The third is a number that was never an IMEI, usually a serial number or an ICCID in the wrong column.
The check digit does not tell you which of the three you are looking at, but it tells you which rows to ask about, and it costs nothing, while paid lookups cost something per query. It also gives you a precise thing to say to the seller: these rows fail the checksum, here is the last digit the calculator expects, please re-pull them from inventory. Most of the time the export was wrong and the deal carries on. For a full list, Bulk IMEI Check does the same job a manifest at a time, and IMEI checks for wholesale buyers covers where the paid checks fit afterwards.
Frequently asked questions
What is an IMEI calculator?
An IMEI calculator works out the fifteenth digit of an IMEI, the check digit, from the first fourteen, and confirms whether the last digit of a full IMEI is the one the formula produces. The calculation is the Luhn formula, the same checksum used on payment card numbers. It is arithmetic on the digits you supply, so it needs no database and no network connection.
How do I calculate the last digit of an IMEI?
Take the first 14 digits. Starting from the second, double every second one and subtract 9 from any doubled value above 9. Add the results. The check digit is whatever you must add to reach the next multiple of ten. For the base 35316105214284 the sum is 46, so the check digit is 4 and the full IMEI is 353161052142844.
Can this calculator tell me the phone model or the owner?
No. It separates the TAC, the first 8 digits allocated by the GSMA, from the 6-digit serial and the check digit, but it holds no device database, so it does not name a model. It holds no ownership, blacklist or lock data either. Those answers come from the GSMA IMEI Database and similar commercial services.
What does a 16-digit number mean?
A 16-digit number is usually an IMEISV, an IMEI Software Version: the same 14-digit base followed by a 2-digit software version rather than a check digit. It turns up in diagnostic screens and in manifests exported from repair systems. The calculator labels the last two digits as the software version and computes the check digit for the base.
Why does my IMEI fail the check digit test?
The three usual causes are a typo, a spreadsheet that damaged the number, and a number that was never an IMEI. Excel stores a 15-digit string as a floating point value and shows it as 3.56938E+14, losing the last digits. The other common case is a serial number or an ICCID sent in the IMEI column.
Can I calculate check digits for a whole manifest?
Yes. Batch mode takes up to 100 lines and returns the input, the mode used, the check digit and the resulting 15-digit IMEI, copyable as tab separated text into a spreadsheet. For validating a longer list of complete IMEIs, the Bulk IMEI Check tool is the manifest-level version of the same arithmetic.
Is the IMEI sent anywhere?
No. Every calculation on this page runs in your browser in JavaScript. Nothing you type is sent to Aikon or to any third party, nothing is logged, and nothing is stored. Once the page has loaded, the calculator works with the network disconnected.
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