The calculator checks a 15-digit IMEI against its check digit, completes a 14-digit number by adding the missing 15th digit, and reads manufacturer and model from the first eight digits (the TAC) where our local TAC database knows them. All three steps run entirely in your browser — the number never leaves the page and is not stored anywhere.
What the calculator cannot do: tell you whether the device has been reported stolen, is locked, or is tied to a carrier. None of that is encoded in the digits — it lives in databases, which is what the IMEI check is for.
An IMEI (International Mobile Equipment Identity) has 15 digits in three blocks. The first eight form the Type Allocation Code (TAC), which identifies the device type and model; its first two digits name the reporting body that allocated the code. Six serial-number digits follow, distinguishing the individual unit within that model, and the check digit closes the number.
Until 2003, digits 7 and 8 were a separate block, the Final Assembly Code (FAC) for the assembly plant. Since 1 April 2004 they are part of the TAC; older numbers often carry the transitional value 00 there. It makes no difference to the check digit, which is always computed over all 14 preceding digits.
| Digits | Block | Meaning |
|---|---|---|
| 1–2 | Reporting Body Identifier | Reporting body that allocated the TAC (e.g. 35 = BABT, 01 = CTIA, 86 = TAF) |
| 3–8 | Rest of the TAC | Together with 1–2 the eight-digit Type Allocation Code: manufacturer and model |
| 9–14 | Serial number (SNR) | Sequential number of the individual unit within the TAC |
| 15 | Check digit (CD) | Computed from digits 1–14 with the Luhn algorithm |
The check digit follows the Luhn formula (ISO/IEC 7812-1), the same scheme used for credit card numbers. Counting from the left, every second digit is doubled — positions 2, 4, 6, 8, 10, 12 and 14. If doubling yields a two-digit number, its digits are added together (16 becomes 7), which is the same as subtracting 9. All 14 values are summed; the check digit is whatever lifts that sum to the next multiple of 10.
Example with 49015420323751: the 14 processed digits sum to 52, the next multiple of 10 is 60, so the check digit is 8. The complete IMEI is 490154203237518. To verify a 15-digit number you run the same calculation, include the 15th digit undoubled — and the total must be divisible by 10 with no remainder.
| Position | Digit | Doubled? | Value |
|---|---|---|---|
| 1 | 4 | no | 4 |
| 2 | 9 | yes → 18 → 9 | 9 |
| 3 | 0 | no | 0 |
| 4 | 1 | yes → 2 | 2 |
| 5 | 5 | no | 5 |
| 6 | 4 | yes → 8 | 8 |
| 7 | 2 | no | 2 |
| 8 | 0 | yes → 0 | 0 |
| 9 | 3 | no | 3 |
| 10 | 2 | yes → 4 | 4 |
| 11 | 3 | no | 3 |
| 12 | 7 | yes → 14 → 5 | 5 |
| 13 | 5 | no | 5 |
| 14 | 1 | yes → 2 | 2 |
The check digit is a safeguard against typing errors, not proof of authenticity. Luhn catches every single mistyped digit and almost every transposition of two adjacent digits (the only exception is 09 ↔ 90). If the calculator reports "invalid", the number has almost always been copied wrongly — it does not mean the device is fake.
Conversely, "valid" only proves that the 15 digits fit together. Whether the device exists, whether it has been reported stolen, whether an iCloud Activation Lock or a SIM lock is active — all of that sits in the databases of the GSMA, the manufacturers and the carriers. Only a lookup answers those questions; ours is free for the basic status and comes with a report for a purchase decision.
Some Android devices, carrier portals and export lists show the IMEI without its check digit, i.e. as 14 digits. Others output the IMEISV: 16 digits where a two-digit software version number (SVN) replaces the check digit at the end. Both are the same device identity, just cut differently. A database check needs the 15-digit form: enter the first 14 digits into the calculator and it adds the check digit.
Do not confuse this with the MEID of CDMA devices: 14 hexadecimal characters (letters A–F are possible) with a different check-digit scheme. This calculator is for IMEIs only.
TACs are allocated by the GSMA through reporting bodies and designate a model, not an individual unit — every iPhone of a given model variant shares the same eight leading digits. Our local database maps many Apple and Samsung TACs to brand, model and sometimes storage or colour; if it does not know a TAC, that only means it is not on file. Whether the TAC matches the device actually in front of you is shown only by comparing it with the device lookup.
The first two digits name the reporting body: 01, 10, 30 and 33 stand for the CTIA (USA), 35 and 44 for the BABT (United Kingdom), 86 for the TAF (China), 91 for the TEC (India), 98 and 99 for the GSMA itself. Most devices sold in Europe start with 35 — that says something about the approval body, nothing about the market the phone was sold in.
Yes. Computing a check digit is arithmetic on a number you already have; the calculator creates no new device identities and alters no device. Reprogramming a phone's IMEI is a different matter: it is a criminal offence in several countries (in the UK since the Mobile Telephones Re-programming Act 2002) and makes a device worthless on the used market. There is no tool for that here.
In almost every case a digit has been copied wrongly or two have been swapped. Also check that you have 15 digits: 14 digits are an IMEI without its check digit, 16 digits are an IMEISV with a software version, 14 characters including letters are an MEID. Only when the number provably comes from the device and still fails is the label or display itself suspect.
No. Validation, check digit and TAC lookup run as JavaScript in your browser against a bundled table; nothing is transmitted and nothing is stored. Only the actual IMEI check on the home page queries databases — and says so.
The IMEI has 15 digits including a check digit. The IMEISV has 16 digits: the same TAC and serial number, but a two-digit software version number instead of the check digit. The MEID is the identifier of CDMA devices, 14 hexadecimal characters. All three identify the hardware, not the user — that is what the IMSI on the SIM card is for.
It is not supposed to happen: every serial number is allocated only once within a TAC. Duplicate IMEIs come from cloning or reprogramming. When such a duplicate is noticed, carriers can block both devices — another reason to run a blacklist check before buying.
No. The check digit knows nothing about the device's history. Devices reported stolen are listed on the GSMA blacklist with their — perfectly valid — IMEI. Only a blacklist check shows whether that is the case.
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