Am always late to learn these tips, but here we go:
Go down in 2s to convert HbA1c from DCCT to IFCC units:
6% = 42 mmol/mol (6, 4, 2)
7% = 53 mmol/mol (7, 5, 3)
8% = 64 mmol/mol
9% = 75 mmol/mol
10% = 86 mmol/mol
11% = 97 mmol/mol
12% = 108 mmol/mol
13% = 119 mmol/mol