Up to a third of mortgage holders and 38% of tenants have never calculated the value of their belongings, a survey by Primary Direct shows.
And about a quarter of those who did take the time, only did so once.
The research also revealed an estimated 5.9 million mortgage holders were potentially under-insured. In addition, 66% of home-owners said they had home contents cover, leaving 3.8 million property owners uninsured.
This is despite the fact that 55% of homeowners said they were very concerned about the threat of burglary. Other concerns given were fire (34%), burst pipes (18%) and being flooded (11%).