Even to the extent that CD rates are correlated with inflation, this can only be the "expected" inflation at the time the CD is bought. The actual inflation will be lower or higher. Locking in the interest rate for a long term may be bad (if inflation goes up) or good (if inflation goes down). For example, in the 1970s, inflation increased higher than it had been, and this was not fully reflected in interest rates. This is particularly important for longer-term notes, where the interest rate is locked in for some time. This gave rise to amusing nicknames for CDs. A little later, the opposite happened, and inflation declined.