Member ages
I.O.I Member Ages and Birthdays
I.O.I member ages and birthdays ranked oldest to youngest, from Nayoung at age 30 to Somi at age 25.
Oldest to youngest
| Rank | Member | Age | Birthday | Position |
|---|---|---|---|---|
| #1 |  NayoungFormer member | 30 | Dec 18, 1995 | Leader, Main Rapper, Lead Dancer, Vocalist |
| #2 |  ChunghaFormer member | 30 | Feb 9, 1996 | Main Dancer, Lead Vocalist, Rapper |
| #3 |  SejeongFormer member | 29 | Aug 28, 1996 | Main Vocalist |
| #4 |  ChaeyeonFormer member | 28 | Dec 1, 1997 | Vocalist, Visual |
| #5 |  KyulkyungFormer member | 27 | Dec 16, 1998 | Lead Dancer, Vocalist, Visual |
| #6 |  SohyeFormer member | 26 | Jul 19, 1999 | Vocalist, Rapper |
| #7 |  YeonjungFormer member | 26 | Aug 3, 1999 | Main Vocalist |
| #8 |  YoojungFormer member | 26 | Nov 12, 1999 | Lead Rapper, Lead Dancer, Lead Vocalist |
| #9 |  DoyeonFormer member | 26 | Dec 4, 1999 | Vocalist, Visual |
| #10 |  MinaFormer member | 26 | Dec 4, 1999 | Lead Dancer, Vocalist, Rapper |
| #11 |  SomiFormer member | 25 | Mar 9, 2001 | Lead Dancer, Lead Vocalist, Rapper, Face of the Group, Center, Maknae |