Are you deciding when to buy a new car? This calculator helps you to determine the right time to buy. How long you should hold onto your car before selling it generally depends on the numbers of years you have owned or will keep the car, and your yearly vehicle expenses (repairs, insurance, and licensing). Other factors are the vehicle's current and future depreciation, its book value, and how much you owe on the vehicle. Included in the analysis is the interest earned from investing the difference in your monthly payments. If you do not feel safe in your car, or it will cost more for repairs than it is worth, it may be time to purchase a new one.