PIN (Postal Index Number) or PIN Code is a 6 digit code identification number given to each Post Office in India. The PIN was introduced on 15th August 1972. In India pincode starts from 1 to 9, the first digit of the pincode ranging from 1 to 8 for geographical regions and digit 9 is reserved for the Army Postal Service. The first 2 digits together indicate the sub-region or postal circle. The first 3 digits together indicate a sorting / revenue district. The last 3 digits refer to the delivery Post Office.

As shown in the above image, the first digit of the PIN code indicates the region. The second digit indicates the sub-region and the third digit indicates the sorting district. The last three digits are assigned to individual post offices within the region.

The 9 PIN zones cover the Indian states and union territories as follows:

1 - Delhi, Haryana, Punjab, Himachal Pradesh, Jammu and Kashmir, Chandigarh
2 - Uttar Pradesh, Uttarakhand
3 - Rajasthan, Gujarat, Daman and Diu, Dadra and Nagar Haveli
4 - Goa, Maharashtra, Madhya Pradesh, Chhattisgarh
5 - Andhra Pradesh, Karnataka, Telangana
6 - Tamil Nadu, Kerala, Puducherry, Lakshadweep
7 - Odisha, West Bengal, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, Andaman and Nicobar Islands, Assam, Sikkim
8 - Bihar, Jharkhand
9 - Army Post office (APO) and Field Post office (FPO)