Pin Code of a state is nothing but the Postal Index Number which is a six digit code that recognizes a postal area. All total India has eight PIN regions. In the six digit of a Pin Code, the first digit indicates the region, the first two indicate the sub region or the postal circle and the first three digit indicate the sorting district. The last three figures indicate the Post Office where the mails are to be delivered.
Bihar being a big state, hosts too many postal circles. And hence there are many Pin Codes in Bihar as per the different areas. Given below is the list of some of the important city names and their Pin Codes at Bihar :
| City Name | Pin Code |
| Araria | 854311 |
| Araria Railway Station | 854312 |
| Arrah | 802301 |
| Aurangabad | 824101 |
| Baidyanadh Deoghar | 814112 |
| Banka | 813102 |
| Begusarai | 851101 |
| Bettaih | 845438 |
| Bhagalpur | 812001 |
| Bhattason | 841460 |
| Bhojpur Naya | 802145 |
| Purana Bhojpur | 802133 |
| Bihar Shariff | 803101 |
| Buzar | 802101 |
| Chapra | 841301 |
| Daltonganj | 822101 |
| Darbhanga | 846004 |
| Dumka | 814101 |
| Gaya | 823001 |
| Gopalganj | 841428 |
| Gumla | 835207 |
| Hajipur | 844101 |
| Hazaribagh | 825301 |
| Hinoo | 834002 |
| Ichwapur | 841411 |
| Ilmasnagar | 848117 |
| Imambari | 846001 |
| Indrapuri | 821308 |
| Islampur | 801303 |
| Jahanabad | 804408 |
| Jahanabad Railway Station | 804417 |
| Karja | 843143 |
| Kathihar | 854105 |
| Laheriasarai | 846001 |
| Madarghat | 854358 |
| Madhubani | 847211 |
| Madhopur | 803218 |
| Madhupur | 815353 |
| Madhepur | 847408 |
| Marhowrah | 841418 |
| Monghyr | 811201 |
| Motihari | 845401 |
| Muzaffarpur | 842001 |
| Nalanda College | 803101 |
| Nalanda Railway Station | 803111 |
| Nawada | 805110 |
| Patna G.P.O | 800001 |
| Purnea | 854301 |
| Ramgarh Cantonment | 829112 |
| Rohtas | 821311 |
| Saharsa | 852201 |
| Samastipur | 848101 |
| Sandha Jahangirpur | 843160 |
| Saraidhela | 828127 |
| Saraiyaganj | 842001 |
| Saraiyahat | 814151 |
| Sasaram | 821115 |
| Sherghati | 824211 |
| Simri | 848516 |
| Sitamarhi | 843301 |
| Siwan | 841226 |
| Sonali | 855114 |
