For homes it's hard to say. I still conservatively list ours at the price we paid 5 years ago, but it's probably gone up from there. You can list a number similar to other homes selling nearby (but you would probably only know asking price, which is not the same as selling price). Alternatively, homes generally keep pace with inflation except in very hot markets, so you could look up inflation values for each year and adjust that way (or a similar fixed value like 3%). For cars, people generally go by Kelly Blue Book. Though some people don't even include cars in their net worth since they are depreciating assets and you can't use the money unless you sell the car.