When ISO 3166-2 first came out in 1998, it listed five divisions, 21 regions, and 64 districts in Bangladesh, specifying which region each district belonged to and which division each region belonged to. The second update to the standard (Newsletter Number I-2) was published on 2002-05-21. It listed only the divisions (now six in number) and the districts. It also changed the spelling of Kishorganj to Kishoreganj. This seems to be correct, so I have made the same change in the table below.

When the FIPS standard first came out in 1970, Bangladesh was listed with no subdivisions. By 1984, it was shown divided into 20 regions. In 1991, the listing changed to show 64 districts - the same districts that are listed in ISO 3166-2. Most recently, Change Notice 1 to FIPS 10-4, dated 1998-12-01, shows nothing but the four divisions (which were already outdated).

Bangladesh is divided into four bibhag (divisions), which are subdivided into anchal (regions), which are further divided into zila (districts), and then into thana or upazila (subdistricts). The regions seem to be diminishing in importance. Therefore, I am presenting the districts as the secondary subdivisions of Bangladesh.

District	HASC	ISO	FIPS	Reg	Population	Area(km.²)
Bagerhat	BD.KH.BH	05	BG22	4L	1,515,815	3,959
Bandarban	BD.CG.BD	01	BG04	2A	292,900	4,479
Barguna	BD.BA.BG	02	BG25	1Q	837,955	1,832
Barisal	BD.BA.BS	06	BG01	1B	2,330,960	2,791
Bhola	BD.BA.BL	07	BG23	1B	1,676,600	3,403
Bogra	BD.RS.BO	03	BG24	5C	2,988,567	2,920
Brahmanbaria	BD.CG.BB	04	BG26	2F	2,365,880	1,927
Chandpur	BD.CG.CP	09	BG27	2F	2,210,162	1,704
Chittagong	BD.CG.CT	10	BG29	2D	6,545,078	5,283
Chuadanga	BD.KH.CD	12	BG30	4M	987,382	1,158
Comilla	BD.CG.CM	08	BG05	2F	4,586,879	3,085
Cox's Bazar	BD.CG.CB	11	BG31	2D	1,757,321	2,492
Dhaka	BD.DA.DH	13	BG32	3G	8,575,533	1,464
Dinajpur	BD.RP.DJ	14	BG33	5H	2,617,942	3,438
Faridpur	BD.DA.FR	15	BG34	3I	1,719,496	2,073
Feni	BD.CG.FN	16	BG35	2O	1,196,219	928
Gaibandha	BD.RP.GB	19	BG36	5S	2,117,959	2,179
Gazipur	BD.DA.GZ	18	BG37	3G	2,026,244	1,741
Gopalganj	BD.DA.GG	17	BG38	3I	1,132,046	1,490
Habiganj	BD.SY.HA	20	BG39	6T	1,757,331	2,637
Jaipurhat	BD.RS.JP	24	BG40	5C	844,814	965
Jamalpur	BD.DA.JM	21	BG41	3J	2,089,366	2,032
Jessore	BD.KH.JS	22	BG42	4K	2,440,693	2,567
Jhalakati	BD.BA.JK	25	BG43	1B	696,055	758
Jhenaidah	BD.KH.JN	23	BG44	4K	1,554,514	1,961
Khagrachari	BD.CG.KG	29	BG45	2E	524,961	2,700
Khulna	BD.KH.KL	27	BG46	4L	2,334,285	4,395
Kishoreganj	BD.DA.KS	26	BG47	3N	2,525,221	2,689
Kurigram	BD.RP.KR	28	BG48	5S	1,782,277	2,296
Kushtia	BD.KH.KU	30	BG49	4M	1,713,224	1,621
Lakshmipur	BD.CG.LK	31	BG50	2O	1,479,371	1,456
Lalmonirhat	BD.RP.LL	32	BG51	5S	1,088,918	1,242
Madaripur	BD.DA.MD	36	BG52	3I	1,137,008	1,145
Magura	BD.KH.MG	37	BG53	4K	811,160	1,049
Manikganj	BD.DA.MK	33	BG54	3G	1,274,829	1,379
Meherpur	BD.KH.ME	39	BG55	4M	579,531	716
Moulvibazar	BD.SY.MB	38	BG56	6T	1,604,028	2,799
Munshiganj	BD.DA.MU	35	BG57	3G	1,293,536	955
Mymensingh	BD.DA.MM	34	BG12	3N	4,439,017	4,363
Naogaon	BD.RS.NA	48	BG58	5R	2,377,314	3,436
Narail	BD.KH.NR	43	BG59	4K	689,021	990
Narayanganj	BD.DA.NY	40	BG60	3G	2,138,492	759
Narsingdi	BD.DA.NS	42	BG61	3G	1,891,281	1,141
Natore	BD.RS.NT	44	BG62	5R	1,521,359	1,896
Nawabganj	BD.RS.NW	45	BG28	5R	1,419,536	1,702
Netrakona	BD.DA.NK	41	BG63	3N	1,937,794	2,810
Nilphamari	BD.RP.NP	46	BG64	5S	1,550,686	1,641
Noakhali	BD.CG.NO	47	BG13	2O	2,533,394	2,601
Pabna	BD.RS.PB	49	BG65	5P	2,153,921	2,371
Panchagarh	BD.RP.PN	52	BG66	5H	829,374	1,405
Parbattya Chattagram	BD.CG.PC	56	BG67	2E	507,180	6,116
Patuakhali	BD.BA.PT	51	BG15	1Q	1,444,340	3,205
Pirojpur	BD.BA.PR	50	BG68	1B	1,126,525	1,308
Rajbari	BD.DA.RB	53	BG69	3I	940,360	1,119
Rajshahi	BD.RS.RS	54	BG70	5R	2,262,483	2,407
Rangpur	BD.RP.RP	55	BG71	5S	2,534,365	2,306
Satkhira	BD.KH.ST	58	BG72	4L	1,843,194	3,858
Shariatpur	BD.DA.SA	62	BG73	3I	1,057,181	1,181
Sherpur	BD.DA.SP	57	BG74	3J	1,246,511	1,364
Sirajganj	BD.RS.SR	59	BG75	5P	2,707,011	2,498
Sunamganj	BD.SY.SN	61	BG76	6T	1,968,669	3,670
Sylhet	BD.SY.SL	60	BG77	6T	2,569,788	3,490
Tangail	BD.DA.TA	63	BG78	3U	3,253,961	3,414
Thakurgaon	BD.RP.TH	64	BG79	5H	1,196,429	1,809
HASC: Hierarchical administrative subdivision codes. The middle two letters identify the division. For key, see Divisions of Bangladesh page. ISO: Codes from ISO 3166-2. For full identification in a global context, prefix "BD-" to the code (ex: BD-57 represents Sherpur). FIPS: Codes from FIPS PUB 10-4. Reg: ISO code for region to which the district belongs (for key to codes, see table below). Population: 2001-01-23 census (source [4]). Capitals: Capitals have the same name as their districts.

Postal codes:

Bangladesh uses a four-digit postal code. The first two digits are the same as the ISO code for the district.

Further subdivisions:

The regions of Bangladesh are listed in the following table. Khagrachari is included in Chittagong Hill Tracts, because that's the way the standards treated it. For a breakout of those two regions, simply use the district figures for Khagrachari and Parbattya Chattagram, respectively.

Region	ISO	FIPS	Population	Area(km.²)
Bandarban	2A	BG04	298,120	4,501
Barisal	1B	BG01	5,864,383	7,299
Bogra	5C	BG02	3,859,752	3,888
Chittagong	2D	BG03	8,385,849	7,457
Chittagong Hill Tracts	2E	BG21	1,033,846	8,679
Comilla	2F	BG05	9,265,040	6,599
Dhaka	3G	BG06	17,192,103	7,470
Dinajpur	5H	BG07	4,693,422	6,566
Faridpur	3I	BG08	6,102,298	6,882
Jamalpur	3J		3,386,751	3,349
Jessore	4K	BG09	5,573,802	6,573
Khulna	4L	BG10	5,792,706	12,168
Kushtia	4M	BG11	3,338,721	3,440
Mymensingh	3N	BG12	9,072,868	9,668
Noakhali	2O	BG13	5,307,529	5,460
Pabna	5P	BG14	4,870,084	4,732
Patuakhali	1Q	BG15	2,309,335	4,095
Rajshahi	5R	BG16	7,624,887	9,456
Rangpur	5S	BG17	9,153,728	9,593
Sylhet	2T	BG18	7,939,343	12,718
Tangail	3U	BG19	3,290,696	3,403
ISO: Codes from ISO 3166-2 (obsolete). FIPS: When FIPS PUB 10-3 came out, Jamalpur was part of Mymensingh. Population: 2001-01-23 census (calculated by adding the districts in each region). Capitals: All capitals have the same name as their region, except that Rangamati is the capital of Chittagong Hill Tracts.

 

The first version of ISO 3166-2 had region codes as shown above. Every region code except Sylhet's started with the digit representing the division to which the region belonged. Sylhet's code should have been 6T to conform with the pattern. ISO never changed it, and in 2002 the list of regions and their codes was dropped from the standard entirely. Since then, Rangpur region has split from Rajshahi, further altering the pattern of adherence.

Change history:

1. ~1946: Patuakhali district split from Bakerganj (now Barisal). Tangail district split from Mymensingh.
2. ~1959: Bandarban district split from Chittagong Hill Tracts.
3. ~1959: Jamalpur district split from Mymensingh. Jamalpur consisted of the western part of the former district of Nasirabad, not including the city of Mymensingh itself.
4. 1971-12-15: Bangladesh became independent. At that date, it had four bibhag (divisions), which were subdivided into zila (districts), and then into thana or upazila (subdistricts).
5. ~1972: Nasirabad and Quaidabad districts merged to form Mymensingh.
6. 1981: Khagrachhari district split from Chittagong Hill Tracts.
7. 1983: Name of Dacca district changed to Dhaka.
8. ~1985: Status of districts (zila) changed to regions (anchal). The regions were subdivided into 64 new, smaller districts, each of which was formed of a set of thana.
9. ~1993: Barisal division formed by taking Barisal and Patuakhali regions from Khulna.
10. ~1998: Sylhet division formed by taking Sylhet region from Chittagong.
11. 2010-01-25: Rangpur division formed by taking Dinajpur and Rangpur regions from Rajshahi.

Other names of subdivisions:

1. Bandarban: Bandarbon (variant)
2. Barguna: Borgona (variant)
3. Barisal: Bakerganj (obsolete)
4. Chittagong: Chattagram (Bengali); Chitagongue (Portuguese-variant)
5. Chittagong Hill Tracts: Parbattya Chattagram (Bengali); Rangamati (variant)
6. Chuadanga: Chaudanga, Choua Danga (variant)
7. Cox's Bazar: Cox Bazar (variant)
8. Dhaka: Daca (Portuguese); Dacca (obsolete)
9. Gaibandha: Gaibanda (variant)
10. Gopalganj: Gopalgonj (variant)
11. Habiganj: Hobiganj, Hobigonj (variant)
12. Jaipurhat: Joypurhat (variant)
13. Jhalakati: Jhalakhati, Jhalkathi, Jhalokati (variant)
14. Jhenaidah: Jhinaidah, Jhinaidha (variant)
15. Khagrachari: Khagrachhari, Ramgarh (variant)
16. Kishoreganj: Kishorganj, Kishorgonj (variant)
17. Kushtia: Kustia (variant)
18. Lakshmipur: Laksmipur, Laxmipur (variant)
19. Manikganj: Manikgonj (variant)
20. Meherpur: Maherpur (variant)
21. Moulvibazar: Maulvi Bazar, Moulabi Bazar, Moulavi Bazar, Moulovibazar (variant)
22. Munshiganj: Munshigonj (variant)
23. Mymensingh: Nasirabad (obsolete)
24. Naogaon: Noagaon (variant)
25. Narail: Narial (variant)
26. Narayanganj: Naray Angonj (variant)
27. Narsingdi: Narshingdi (variant)
28. Natore: Nador (Portuguese-variant); Nator (variant)
29. Nawabganj: Chapai Nababgonj, Chapai Nawabganj, Chapai Nowab Ganj (variant)
30. Netrakona: Netrokona (variant)
31. Nilphamari: Nilphamary (variant)
32. Pabna: Pabhna (variant)
33. Panchagarh: Panchagar, Panchagor, Panchgarh (variant)
34. Parbattya Chattagram: Chittagong Hill Tracts (English); Rangamati (variant)
35. Rangpur: Rongpur (variant)
36. Satkhira: Shatkhira (variant)
37. Shariatpur: Sariatpur, Shariyatpur (variant)
38. Sirajganj: Sirajgonj (variant)
39. Sunamganj: Sun Amgonj (variant)
40. Thakurgaon: Thakoregaon (variant)

Population history:

Region	1901	1911	1921	1931	1941	1951-03-01	1961-02-01	1974-03-01	1981-03-06	1991-03-11	2001-01-23
Bandarban								116,000	171,000	231,000	298,120
Barisal	2,484,878	2,612,806	2,843,914	3,194,455	3,810,974	2,635,797	3,068,121	3,928,000	4,667,000	5,413,000	5,864,383
Bogra	884,079	1,016,782	1,082,750	1,121,954	1,260,463	1,278,185	1,574,105	2,231,000	2,728,000	3,434,000	3,859,752
Chittagong	1,468,377	1,628,085	1,740,306	1,936,389	2,331,481	2,511,785	2,982,931	4,315,000	5,491,000	6,715,000	8,385,849
Comilla	2,138,664	2,454,744	2,695,702	3,056,300	3,860,139	3,792,200	4,388,906	5,819,000	6,881,000	8,207,000	9,265,040
Dhaka	2,617,340	2,929,389	3,171,524	3,449,293	4,223,532	4,072,781	5,095,745	7,612,000	10,014,000	13,232,000	17,192,103
Dinajpur	1,125,597	1,167,706	1,219,613	1,234,224	1,335,588	1,354,432	1,709,917	2,571,000	3,200,000	3,983,000	4,693,422
Faridpur	1,809,542	1,956,444	2,058,783	2,192,015	2,682,701	2,774,345	3,178,945	4,060,000	4,764,000	5,424,000	6,102,298
Jamalpur								2,059,000	2,452,000	3,013,000	3,386,751
Jessore	1,618,630	1,568,790	1,557,463	1,522,868	1,662,646	1,638,387	2,190,151	3,327,000	4,020,000	4,848,000	5,573,802
Khagrachari										343,000	525,664
Khulna	1,267,720	1,379,818	1,471,860	1,629,430	1,944,418	2,075,506	2,448,720	3,557,000	4,329,000	5,039,000	5,792,706
Kushtia	885,079	841,860	782,992	807,725	919,543	884,157	1,166,262	1,884,000	2,292,000	2,801,000	3,338,721
Mymensingh	3,922,247	4,530,881	4,842,467	5,135,264	6,029,533	4,557,939	5,532,318	5,508,000	6,568,000	7,994,000	9,072,868
Noakhali	1,027,785	1,183,789	1,347,902	1,567,368	2,039,217	2,071,144	2,383,145	3,234,000	3,816,000	4,626,000	5,307,529
Pabna	1,417,839	1,425,124	1,385,321	1,437,998	1,696,149	1,584,303	1,959,060	2,815,000	3,424,000	4,184,000	4,870,084
Patuakhali						1,006,388	1,193,648	1,499,000	1,843,000	2,050,000	2,309,335
Rajshahi	1,902,317	2,000,161	2,027,591	1,993,280	2,198,081	2,205,057	2,810,964	4,288,000	5,270,000	6,594,000	7,624,887
Rangamati	124,762	153,830	173,243	212,922	247,053	287,274	385,079	392,000	580,000	401,000	508,182
Rangpur	2,202,018	2,434,009	2,554,945	2,646,285	2,923,879	2,916,476	3,796,043	5,447,000	6,510,000	8,015,000	9,153,728
Sylhet	2,030,912	2,240,838	2,297,720	2,466,410	2,831,900	3,059,367	3,489,589	4,759,000	5,656,000	6,765,000	7,939,343
Tangail						1,226,806	1,486,588	2,078,000	2,444,000	3,003,000	3,290,696
Totals	28,927,786	31,555,056	33,254,096	35,604,170	41,997,297	41,932,329	50,840,325	71,479,000	87,120,000	106,315,000	124,355,263
Column headings are census dates, except 1998, which has provisional population data for 1998. Where cells are empty, the change history (above) should explain why. Before 1974, data for Nasirabad and Quaidabad are combined and listed under Mymensingh.

Sources:

1. [1] Statistical Abstract of Bangladesh, SOCOM Research Bureau, Society & Commerce Publications Private Ltd., Calcutta, March, 1975. Lists population data for 1901-1961. I'm not sure that the same regions existed throughout the period 1901-1941; those populations might have been calculated proleptically by agglomerating the populations of smaller units, to cover the same areas as the regions.
2. [2] Bangladesh Bureau of Statistics: Preliminary Report  on the 2001 census is the source for population data for 1974-1991.
3. [3] Bangladesh National Data Bank  (retrieved 2001-03-22) has provisional population data for 1998.
4. [4] Bangladesh Bureau of Statistics  (retrieved 2011-03-10) is the source for all 2001 population figures shown.