More than a third (35%) of people aged between 45 and 64 have no idea what their workplace pension is worth, according to research.
Based on interviews with 3,100 people, pension provider Partnership said another 21% admitted they did not have a workplace pension at all.
Concerning private pensions, the research found 23% of people did not know its value, while a third did not have one.
Partnership said respondents showed "worrying levels of ignorance" around the full value of other types of savings, with 25% not knowing the value of their easy access savings and 24% not knowing how much their fixed-term savings were worth.
Partnership said even people closer to retirement, those aged between 55 and 64, did not demonstrate a better understanding of their assets.
Respondents in this age group had not prepared for their retirement savings, with 28% not having a private pension and 20% not having a workplace pension, according to the survey. The firm said the figures suggested these people would be "heavily reliant" on state pensions.
Andrew Megson, managing director of retirement at Partnership, said: "Planning for the various retirement eventualities is hard enough when you know exactly how much you do have but it is likely to be almost impossible if you don't even know that.
"While it may take a little time, getting a better understanding of the value of your total assets will allow you to take practical steps to improve your retirement before it is too late. Lack of preparation can mean that people's choices are restricted and they may need to make some very difficult decisions at retirement."