When an accident causes extensive or costly damage to your vehicle, it is possible your vehicle will be declared a total loss.
Insurance companies' total loss procedures may differ but normally they take into consideration business experience, state laws and regulations. In general, your vehicle is considered a total loss when the cost to return the vehicle to pre-accident condition would be as much, or more, than the actual cash value of the car.
There are a few variations, but typically if the cost of repairing the vehicle, plus its salvage value, plus rental reimbursement expense during repair equals or exceeds its actual cash value, it is not economically feasible to repair the vehicle will be found to be a total loss.
Many claims adjusters will find a vehicle to be totaled when the repair cost, plus the salvage value (money the insurer would recoup when selling the vehicle through a licensed salvage vendor) exceeds the vehicle's actual cash value, or if state regulations warrant the car to be totaled out.
There may be certain things that insurance adjusters will look for that would cause a car to be "totaled out" but this would differ by state laws and the insurance company's guidelines. But if a mechanic cannot make repairs for the vehicle to be safely put back on the road then it would normally be found to be a total loss.
To find out if your state requires a car to be totaled out for certain damages ask your state's insurance regulator. As for your insurance company's guidelines for finding a car a total loss, discuss this issue with your agent or claims adjuster.