Decode an Indonesian NIK: birth date, gender, and region from the ID number

What a NIK is and how many digits it has

NIK stands for Nomor Induk Kependudukan, the single, unique identity number attached to every person registered as a resident of Indonesia. Its legal basis is Law No. 23 of 2006 on Population Administration, amended by Law No. 24 of 2013. The number is issued by the civil registry office (Dukcapil) through the Ministry of Home Affairs' SIAK system.

Three properties matter most:

• Issued once, valid for life. Moving, marrying, replacing the card, or losing it: the NIK stays the same.
• Assigned at birth. A baby receives a NIK when the birth is registered on the family card and birth certificate, long before the ID card is issued at 17.
• One person, one NIK. Electronic ID enrolment with fingerprints and iris scans is used to find duplicate NIKs, after which one is deactivated.

How many digits?

Always 16 digits, no letters, no spaces. A number with more or fewer digits is not a NIK, or was mistyped. Do not confuse it with numbers often requested alongside it: the student number NISN has 10 digits, the family card number (KK) has 16 digits but different values, and the tax number NPWP now uses the same 16 digits as the NIK.

A little history: nationwide single numbering followed the 2006 law. Electronic ID cards (KTP-el) were enrolled en masse from 2011, and since 2013 they are valid for life. The digital version, the IKD app, was introduced in 2022.

The 16-digit structure

A NIK is not a random string. Its sixteen digits fall into three segments with the same pattern for everyone, as set out in the implementing regulation of the population law (Government Regulation No. 37 of 2007).

1. First six digits: region

   Two digits for the province, two for the regency or city, two for the district. Regencies are numbered 01 to 69 and cities from 71, so the middle pair alone tells you city or regency. The code marks where the NIK was created, not where the person lives now. For a baby it is usually the parents' address on the family card.

2. Middle six digits: birth date

   The format is DDMMYY. If the day is above 40, the holder is a woman and the real day is that number minus 40. Example: 63 means the 23rd, female. The year is written with two digits only.

3. Last four digits: the meaning of the final numbers

   This serial distinguishes people born on the same date and registered in the same district. The first person gets 0001, the next 0002, and so on. Large serials, say 0100 and above, are rare.

Reading a NIK: where and when someone was born

A NIK tells you two things: the region where it was issued (usually where the parents lived at birth, not necessarily the birthplace), and the date of birth. Take the example above, 1271182308840005, segment by segment:

1. 12 is Sumatera Utara (North Sumatra).
2. 71 within Sumatera Utara is Kota Medan. The number 71 immediately tells you it is a city, not a regency.
3. 18 within Kota Medan is the district of Medan Perjuangan.
4. 23 is below 40, so the holder is male and was born on the 23rd.
5. 08 is August, and 84 is read as 1984.
6. 0005 means he was the fifth person registered in Medan Perjuangan with the birth date 23 August 1984.

Now a female example: 3275014505920012. The region segment is 32 (Jawa Barat), 75 (Kota Bekasi), 01 (Bekasi Timur). The day segment is 45, above 40, so female, and the real day is 45 minus 40, which is 5. Month 05 is May, year 92 reads as 1992. The serial is 0012. Conclusion: female, born 5 May 1992, registered in Bekasi Timur, Kota Bekasi. Paste that number into the boxes above and compare.

Male and female NIKs: the difference

The only difference is in the two day-of-birth digits (digits 7 and 8). On a man's NIK the digits are the day as is, 01 to 31. On a woman's NIK, 40 is added, giving 41 to 71. The six region digits, month, year, and serial are not gendered.

The rule is simple: if the number is above 40, the holder is female and the real day is that number minus 40. Values 32 to 40 never appear in a valid NIK.

Cases that often confuse people

Why do women's NIKs add 40?

It is not an error. Dukcapil adds 40 to a woman's day of birth so that gender is encoded in the number without an extra digit. The range is 41 to 71, meaning days 1 to 31.

The year has only two digits

84 could mean 1984 or 2084, and 05 could mean 1905 or 2005. This tool guesses with a simple rule: if the 20xx year has not passed the current year, it reads 20xx; otherwise 19xx. The guess is wrong only for people over a hundred years old.

Regions that have since been split

The region code in a NIK is the code at the time of issue. When an area is split, the new area gets a new code, but old NIKs are not changed. The biggest example: in 2022 Papua was split into several new provinces with codes 93 to 96. People whose NIKs were issued before that still carry 91 or 92, and their regency code may no longer be in the current list. This tool marks that as "unknown", even though the NIK is valid.

The address on the card differs from the NIK region

Normal. Once you move and get a new card, the address is updated but the NIK stays, old region code included. The NIK region is history, not the current address.

The NIK is rejected as unregistered during verification

Banks, mobile operators, or apps sometimes reject a valid NIK. Common causes are data not yet consolidated centrally, a spelling or date mismatch with the Dukcapil database, or the NIK being caught in a data clean-up. The fix is a visit to the local Dukcapil office with the family card, or one of the official channels above.

Newborns and children

A NIK is assigned when the birth is registered: once the birth certificate is issued and the baby is added to the family card, the NIK exists, with the region code of the parents' registration. Children under 17 can get a child identity card (KIA) carrying the same NIK. The electronic ID card is issued at 17 or upon marriage, and the NIK does not change. When a school asks for a child's NIK, look at the NIK column in that child's row on the family card. The NIK is not the NISN: the NISN is a 10-digit student number for education records, while the NIK is the 16-digit civil registry number.

Twins

Twins never share a NIK. Born on the same date and registered in the same district, same-sex twins share the first twelve digits, because the region and birth date are the same. For boy-girl twins even the day digits differ, since 40 is added to the girl's day. What separates them is the last four digits, the serial: for example 0001 and 0002.

Foreign nationals

Foreigners holding a permanent stay permit (KITAP) also receive a NIK and an electronic ID card with the same 16-digit structure. The difference is that their card has an expiry date tied to the permit rather than being valid for life.

Duplicate NIKs

This happened to people who registered in two regions before electronic enrolment. The biometric system finds the duplicate and deactivates one NIK. If you ever held two ID cards, make sure the active NIK is the one on your current family card.

How to find your own NIK

Lost your ID card, or never had one? Your NIK appears on other documents, because the number is the same everywhere.

• Family card (KK). There is a NIK column next to every family member's name. This is the fastest way.
• Birth certificate and KIA. Newer certificates and the child identity card show the NIK.
• IKD app. If you have activated it, your ID data including the NIK shows on your phone.
• Dukcapil. Call Halo Dukcapil 1500-537 or use the official WhatsApp with your full name and family card number. If every document is lost, visit the local Dukcapil office.

What is not possible: looking up a NIK from a name or birth date alone. No public service does that, and any site offering it should be treated with suspicion.

Which phone numbers are registered under my NIK?

Each operator keeps a list of prepaid numbers registered with your NIK, up to three per operator. Operators are required to provide a number-check facility; the check is made from the operator's own number, for example SMS INFO#NIK to 4444 for Indosat or *123*4444# for XL. The full list per operator is in the official channels section above. If a number is not yours, ask the operator to remove it.

Can a NIK be checked online?

Confirming that a NIK is registered is only possible through Dukcapil, whether via the IKD app, WhatsApp, SMS, phone, or its official accounts. The tool on this page reads the meaning of the digits, not the registration status.

What the NIK is used for

The NIK has become the primary key for almost every service that needs to know who you are:

• Tax. For resident individuals, the NIK serves as the tax number (NPWP) once matched; tax services have used it since 1 July 2024. Company NPWPs use a different 16-digit form, the old 15-digit number with a 0 in front. The NPWP converter tells the two apart.
• Prepaid SIM cards. Until mid-2026, registration used the NIK and family card number, up to three numbers per operator. Since 1 July 2026 new subscribers are verified with facial biometrics; existing numbers stay recorded under the NIK.
• National health insurance (BPJS Kesehatan). The NIK is used as the participant number.
• Banks, e-wallets, and lenders. Identity verification (KYC) always asks for the NIK, often with a photo of the card and a selfie.
• Social assistance. Beneficiary data is keyed to the NIK.
• Elections. Voter rolls are built from NIKs.
• School, driving licence, passport, employment. School enrolment, licence and passport applications, and HR administration all reference the NIK.

Real or fake NIK: what you can and cannot check yourself

Two different questions are often mixed up. First, does the digit structure make sense? Second, is the number actually registered to the person claiming it? The first you can check yourself in seconds; the second can only be answered by Dukcapil.

Signs of a made-up NIK

• Not 16 digits, or contains letters.
• A province code that is not in the list (for example starting with 00, 10, or 99).
• Day digits 32 to 40, or above 71. A month above 12. A date that does not exist, such as 31 February.
• Serial number 0000.

The tool above checks all of these. If a number passes, the stamp says "format OK". That does not mean genuine: a carefully invented NIK still passes a format check.

Confirming that a NIK is registered

Match the NIK, name, and birth date through Dukcapil: the IKD app, WhatsApp 0813-2691-2479, phone 1500-537, or its official accounts. For tax purposes, the DJP portal validates a NIK against population data during NPWP matching. Any site or person claiming to confirm authenticity from the digits alone cannot be trusted.

What cannot be read from a NIK

• Name, full address, mother's name, and photo. These exist only in the Dukcapil database, not in the digits. Any site claiming to show a name from a NIK alone deserves suspicion.
• Authenticity. A number with the right structure is readable even if it was never issued. Confirming registration is only possible through Dukcapil.
• Current residence. The region code is where the NIK was first created.
• Place of birth. The region code is the place of registration, which is often but not always the birthplace.
• Blood type, religion, marital status, occupation, nationality. Printed on the card, but not stored in the NIK.

Age, weekday, and weton

Once the birth date is read, three more things can be computed. Age is counted from the birth date to today according to your device's clock, in years, months, and days. Weekday follows the ordinary Gregorian calendar.

Weton combines the seven-day week with the five-day Javanese market cycle (pasaran: Legi, Pahing, Pon, Wage, Kliwon). Both cycles run continuously, so each combination repeats every 35 days. Each day and each pasaran has a value called neptu, and their sum is the weton's neptu.

This tool computes the pasaran from the reference date 17 August 1945, a Friday Legi, and runs the five-day cycle forward or backward. The example above, 23 August 1984, falls on Thursday Pahing with neptu 8 + 9 = 17. Weton is part of Javanese tradition; this tool only calculates, it does not interpret.

Making a sample KTP from a NIK

The card above holds only what the NIK stores. If you need a full sample card with a name, address, religion, occupation, and even a photo, for example for a design mockup, app testing, or teaching, use the Sample KTP page. The NIK you typed here comes along. There, the fields read from the NIK stay locked, the whole card is covered by the watermark "Sample only, NOT a real KTP", the signature reads Sample, and the result downloads as PNG, JPG, WebP, or PDF at real card size.

A column of NIKs in Excel?

For a column of NIKs in Excel or Google Sheets, the Excel formulas for birth date from a NIK, gender, age, and region code are on the bulk NIK page, together with how to stop Excel turning a NIK into 1.27E+15. The same page reads hundreds of NIKs at once without formulas.

Protecting a NIK from misuse

A NIK is not strictly secret. It is printed on many documents, requested by many services, and has leaked in several large data breaches. The danger is when the NIK is combined with other data: the family card number, mother's maiden name, a photo of the ID card, and a selfie. That bundle is what opens bank accounts, takes out online loans, or hijacks phone numbers.

1. Do not post photos of your ID card on social media or in chat groups. If a service requires one, add a watermark with the service name and date, and send it only through the official channel.
2. Treat your family card number and mother's maiden name like passwords. Both are used as security questions in many places.
3. Never share a one-time code, whatever the reason. Genuine staff never ask for it.
4. Check your credit history in OJK's SLIK regularly. It is free, and the only way to be sure there is no loan in your name.
5. Activate the IKD app so your ID data is visible on your phone and changes can be monitored.
6. If misuse has already happened: get the SLIK evidence, report to OJK and the police, then ask the provider to block the account that is not yours. The official channels are in the section above.

Common misconceptions

• "You can get a name and address from a NIK." You cannot. Only Dukcapil and the institutions working with it hold that data.
• "The last four digits are random." They are an issuance serial, starting at 0001.
• "The NIK region code is the current address." It is where the NIK was issued. The current address is on the card, not in the NIK.
• "The NIK changes when you move or replace the card." The NIK is valid for life and never replaced.
• "The NIK and the family card number are the same thing." Different. The NIK belongs to a person; the KK number belongs to a family. The structures are similar, the digits differ.
• "NIK checker sites can confirm authenticity." Any site, including this one, can only read the digit structure. Authenticity can only be confirmed by Dukcapil.
• "A woman's NIK is misprinted because the day is 45." That is the add-40 rule for women, not an error.