When you insure your vehicle, the insurance company only insures the repairs up to a certain amount. If the cost of repairs would be higher than that amount, the car is considered a total loss, and the settlement will be for the current value of the car. The thing to remember is that the current value of your car may be higher than the total loss threshold, but the insurance company will deem it to be beyond repair, to keep the costs within statistical brackets.
The percentage of the actual vehicle value that must be damaged ranges from 60% upwards, with the determination set by law in some states or by the individual insurer in others. In states where the insurer makes the determination of the damage to value percentage, most insurers use 70%, but check with your insurer if you have any questions.