| Code | County | Former Province |
Area (km2) |
Population (2009 Census) |
Population (2019 Census) |
Capital | Postal
Abbreviations |
|---|---|---|---|---|---|---|---|
| 1 | Mombasa | Coast | 212.5 | 939,370 | 1,208,333 | Mombasa | MSA |
| 2 | Kwale | Coast | 8,270.3 | 649,931 | 866,820 | Kwale | KWL |
| 3 | Kilifi | Coast | 12,245.9 | 1,109,735 | 1,453,787 | Kilifi | KLF |
| 4 | Tana River | Coast | 35,375.8 | 240,075 | 315,943 | Hola | TRV |
| 5 | Lamu | Coast | 6,497.7 | 101,539 | 143,920 | Lamu | LMU |
| 6 | Taita–Taveta | Coast | 17,083.9 | 284,657 | 340,671 | Wundanyi | TVT |
| 7 | Garissa | North Eastern | 45,720.2 | 623,060 | 841,353 | Garissa | GRS |
| 8 | Wajir | North Eastern | 55,840.6 | 661,941 | 781,263 | Wajir | WJR |
| 9 | Mandera | North Eastern | 25,797.7 | 1,025,756 | 867,457 | Mandera | MDR |
| 10 | Marsabit | Eastern | 66,923.1 | 291,166 | 459,785 | Marsabit | MRS |
| 11 | Isiolo | Eastern | 25,336.1 | 143,294 | 268,002 | Isiolo | ISL |
| 12 | Meru | Eastern | 7,003.1 | 1,356,301 | 1,545,714 | Meru | MRU |
| 13 | Tharaka-Nithi | Eastern | 2,609.5 | 365,330 | 393,177 | Kathwana | TNT |
| 14 | Embu | Eastern | 2,555.9 | 516,212 | 608,599 | Embu | EMB |
| 15 | Kitui | Eastern | 24,385.1 | 1,012,709 | 1,136,187 | Kitui | KTU |
| 16 | Machakos | Eastern | 5,952.9 | 1,098,584 | 1,421,932 | Machakos | MCK |
| 17 | Makueni | Eastern | 8,008.9 | 884,527 | 987,653 | Wote | MKN |
| 18 | Nyandarua | Central | 3,107.7 | 596,268 | 638,289 | Ol Kalou | NDR |
| 19 | Nyeri | Central | 2,361.0 | 693,558 | 759,164 | Nyeri | NYR |
| 20 | Kirinyaga | Central | 1,205.4 | 528,054 | 610,411 | Kerugoya | KRG |
| 21 | Murang'a | Central | 2,325.8 | 942,581 | 1,056,640 | Murang'a | MRG |
| 22 | Kiambu | Central | 2,449.2 | 1,623,282 | 2,417,735 | Kiambu | KMB |
| 23 | Turkana | Rift Valley | 98,597.8 | 1,100,399 | 1,504,976 | Lodwar | TRK |
| 24 | West Pokot | Rift Valley | 8,418.2 | 512,690 | 621,241 | Kapenguria | WPK |
| 25 | Samburu | Rift Valley | 20,182.5 | 223,947 | 310,327 | Maralal | SBR |
| 26 | Trans-Nzoia | Rift Valley | 2,469.9 | 818,757 | 990,341 | Kitale | TNZ |
| 27 | Uasin Gishu | Rift Valley | 2,955.3 | 894,179 | 1,163,186 | Eldoret | UGS |
| 28 | Elgeyo-Marakwet | Rift Valley | 3,049.7 | 369,998 | 454,480 | Iten | EMK |
| 29 | Nandi | Rift Valley | 2,884.5 | 752,965 | 885,711 | Kapsabet | NDI |
| 30 | Baringo | Rift Valley | 11,075.3 | 555,561 | 666,763 | Kabarnet | BRG |
| 31 | Laikipia | Rift Valley | 8,696.1 | 399,227 | 518,560 | Rumuruti | LKP |
| 32 | Nakuru | Rift Valley | 7,509.5 | 1,603,325 | 2,162,202 | Nakuru[8][9] | NKR |
| 33 | Narok | Rift Valley | 17,921.2 | 850,920 | 1,157,873 | Narok | NRK |
| 34 | Kajiado | Rift Valley | 21,292.7 | 687,312 | 1,117,840 | Kajiado | KJD |
| 35 | Kericho | Rift Valley | 2,454.5 | 752,396 | 901,777 | Kericho | KRC |
| 36 | Bomet | Rift Valley | 1,997.9 | 730,129 | 875,689 | Bomet | BMT |
| 37 | Kakamega | Western | 3,033.8 | 1,660,651 | 1,867,579 | Kakamega | KKG |
| 38 | Vihiga | Western | 531.3 | 554,622 | 590,013 | Mbale | VHG |
| 39 | Bungoma | Western | 2,206.9 | 1,375,063 | 1,670,570 | Bungoma | BGM |
| 40 | Busia | Western | 1,628.4 | 743,946 | 893,681 | Busia | BSA |
| 41 | Siaya | Nyanza | 2,496.1 | 842,304 | 993,183 | Siaya | SYA |
| 42 | Kisumu | Nyanza | 2,009.5 | 968,909 | 1,155,574 | Kisumu | KSM |
| 43 | Homa Bay | Nyanza | 3,154.7 | 963,794 | 1,131,950 | Homa Bay | HBY |
| 44 | Migori | Nyanza | 2,586.4 | 917,170 | 1,116,436 | Migori | MGR |
| 45 | Kisii | Nyanza | 1,317.9 | 1,152,282 | 1,266,860 | Kisii | KSI |
| 46 | Nyamira | Nyanza | 912.5 | 598,252 | 605,576 | Nyamira | NMR |
| 47 | Nairobi | Nairobi | 694.9 | 3,138,369 | 4,397,073 | Nairobi | NBI |
| 581,309.0 | 38,610,997 | 47,564,296 | Nairobi |
