There are nuances to the data: for workers aged 55 and over, the average 401(k) balance is $143,300, while those workers 55 and over who have been lucky to continuously contributed their 401(k) for at least 10 years have an average balance of some $243,800.f you add in their employer match, the average savings rate for each of those groups was: 14.9%, 14.2% and 13.6%, respectively, according to Fidelity. Workers aged 35 to 39 saved 7.2% on average (10.4% with the employer match). Those aged 40 to 44 saved 7.6% (10.9% with the match).