Level 1
Beginner (A1) - IELTS level : not enough
Level 2
Pre-intermediate (A2) - IELTS level: -
Level 3
Intermediate (B1) - IELTS level: 4/4.5/5
Level 4
UpperIntermediate(B2)- IELTS level: 5.5/6/6.5
Level 5
Advanced (C1)- IELTS level: 7/7.5/8