Spanish DNI/NIE Letter Calculator Online: Free, Official
Compute the letter of your Spanish DNI or NIE with the official algorithm (modulo 23), or validate a full ID.
Calculate the letter of the Spanish DNI with the modulo-23 algorithm, including NIE numbers for foreigners (X, Y, Z). Check your ID is written correctly.
By VOV · Last updated: October 21, 2026
How it works
The letter is computed with the official modulo 23 operation: the number is divided by 23 and the remainder (0–22) indexes into «TRWAGMYFPDXBNJZSQVHLCKE». For NIE, the leading letter is first converted (X→0, Y→1, Z→2). The calculation is instant and 100% local.
Use cases
- Calculate the letter of your Spanish DNI to complete your passport renewal application form correctly
- Verify a foreign employee's NIE letter before officially registering them with Spain's Social Security system
- Get the letter matching your ID number so you can fill out your income tax return correctly
Frequently asked questions
How is the DNI letter computed?
The 8-digit number is divided by 23 and the remainder (0–22) is looked up in the official table TRWAGMYFPDXBNJZSQVHLCKE.
What about the NIE letter?
The initial letter is replaced by a number (X→0, Y→1, Z→2) and the same modulo 23 is applied to the resulting 8-digit number.
Does the letter distinguish people?
Yes: number + letter uniquely identify each citizen. Two people never share the same DNI.
What if my letter doesn't match the one on my DNI?
Double-check that you typed the 8 digits correctly, with no spaces or extra zeros. If the number is right and the letter differs, the physical document prevails: it may be a printing error to fix at the police station.
Is the DNI letter mandatory for official procedures?
Yes, the full DNI always includes the letter: forms, contracts and banking procedures require it. Without the letter the document counts as incomplete and many systems reject it automatically.