How long should a seat belt be?

A seat belt should be long enough to comfortably and securely fit across the occupant’s lap and shoulder without being too tight or too loose. Typically, a lap belt should lie flat across the upper thighs, while the shoulder belt should rest across the chest and collarbone. For optimal safety, the seat belt should not twist or have any slack. It's essential that the seat belt allows for movement but still keeps the occupant restrained in the event of a crash.