How to use it
- Type the 15-digit IMEI from the box, the settings menu or the phone's information screen. Spaces and hyphens do not matter.
- Read Result: green means the 15th digit is the check digit that the Luhn formula gives.
- If it is red, compare each digit with the number on the box. A mistyped digit is the usual cause.
- Read How the check digit was worked out to see each step, and Type Allocation Code (TAC) for the first eight digits.
How the IMEI check digit is calculated
An IMEI has 15 decimal digits: an eight-digit Type Allocation Code (TAC), a six-digit serial number and a check digit. The specification says the check digit is there to avoid manual transmission errors, for example when customers register stolen phones at the operator's customer care desk.
The check digit is worked out from the first 14 digits with the Luhn formula that 3GPP TS 23.003 describes in its Annex B. The digits are counted from the right, and each step adds one of the three figures below.
CD = (10 − total mod 10) mod 10
total = (digits of the doubled values) + (the other digits)
doubled: the digits in places 1, 3, 5 ... 13, counted from the right
of the first 14 digits; a value above 9 counts as its two digits- Place 1 is the last digit of the serial number, so the check digit depends on every digit before it.
- If the total ends in 0, the check digit is 0, as Step 3 of Annex B.2 says.
What the TAC and the serial number are
The Type Allocation Code is issued by the GSM Association (GSMA), which acts as the Global Decimal Administrator. Manufacturers give serial numbers in sequence within each code.
The page reads the two parts from the digits you type and shows them. It does not connect to any register, so it cannot say which maker or model a TAC belongs to.
What a valid check digit does not show
- A correct check digit shows that the 15 digits are well formed. It does not show that the phone exists, is genuine or is not blocked.
- Whether a phone is reported stolen or blocked is checked by mobile operators and national registers, which this page does not contact.
- A 16-digit IMEISV, which adds a two-digit software version, is not the 15-digit IMEI this tool checks.
Worked example: 260531793113837
The TAC is 26053179 and the serial number is 311383. The first 14 digits are 26053179311383, and the Luhn formula gives the check digit 7, the same value as the example in Annex B.3 of TS 23.003.
Doubling the digits in places 13, 11 ... 1 gives 12, 10, 2, 18, 2, 6, 6. Their digits add up to 29, the other digits to 24, so the total is 53. The check digit is (10 − 3) mod 10 = 7, and the 15th digit typed, 7, matches it.
| Item | Value |
|---|---|
| Type Allocation Code (TAC) | 26053179 |
| Serial number | 311383 |
| Doubled values | 12, 10, 2, 18, 2, 6, 6 |
| Total | 53 |
| Check digit | 7 |
| Result | Valid |
Frequently asked questions
What is the check digit of an IMEI?
It is the 15th digit. The Luhn formula gives it from the first 14 digits, so a single mistyped digit in those 14 usually changes the result and the page shows a red mismatch.
Why can the check digit be 0?
When the total of the doubled and the other digits ends in 0, the check digit is 0. Step 3 of Annex B.2 of TS 23.003 gives this rule, and the all-zero IMEI is an example.
What does the Type Allocation Code tell me?
The first eight digits are the TAC. The GSM Association issues it as Global Decimal Administrator, so the code shows who received the allocation, not the model you hold.
Does a valid IMEI mean the phone is not stolen?
No. The check only shows that the digits are well formed. Whether a phone is blocked or reported stolen is for the mobile operator or a national register to decide, and this page contacts neither.
Why does the page not show the phone model?
The page works only from the digits you type. A model lookup needs a database this tool does not have, and nothing you type is sent to any registry or to us.
Does the page keep the IMEI I type?
No. The check runs in your browser, and nothing you type is stored or sent to us.
Sources
Figures and text last checked on Thursday, November 12, 2026.