About

This tool generates mathematically valid CPF (Cadastro de Pessoas Físicas) numbers for software testing, database verification, and QA processes. It utilizes the standard Modulus 11 algorithm defined by the RFB (Receita Federal do Brasil) to calculate the two check digits (J and K). These numbers satisfy the checksum requirements but do not correspond to real individuals.

The tool also allows you to simulate CPFs from specific fiscal regions by fixing the 9th digit. Incorrect implementation of CPF validation is a common source of bugs in Brazilian e-commerce and fintech applications; this generator ensures your test data is accurate.

Formulas

A CPF number consists of 9 base digits and 2 verifier digits: d₁...d₉-J K.

Step 1: Calculate First Check Digit (J)

S₁ = 8∑i=0 d_i × (10 - i)

Then, the digit J is determined by the remainder:

r = (S₁ × 10) % 11

If r = 10, then J = 0; otherwise J = r.

Step 2: Calculate Second Check Digit (K)

S₂ = 9∑i=0 d_i × (11 - i)

Similar to the first step, K is derived from S₂.

Reference Data

9th Digit	Fiscal Region (States)
1	DF, GO, MS, MT, TO
2	AC, AM, AP, PA, RO, RR
3	CE, MA, PI
4	AL, PB, PE, RN
5	BA, SE
6	MG
7	ES, RJ
8	SP
9	PR, SC
0	RS

Frequently Asked Questions

No. These numbers are mathematically valid but are not registered in the official government database. Attempting to use them for credit applications or legal documents will fail background checks.

The 9th digit of the CPF (the one before the dash) indicates the fiscal region where the number was issued. For example, if the 9th digit is 8, the CPF is from São Paulo.

It is statistically possible. The last two digits are calculated based on the first nine. "00" is just as valid as "54" or "91", provided the Modulus 11 checksum calculation is correct.

You must implement the Modulus 11 algorithm. Do not rely solely on Regex or length checks, as they cannot verify if the number is authentic. You must calculate the checksums J and K and compare them to the input.