Jump-starting a dead battery typically doesn't take much time, but the exact duration can vary depending on several factors. It usually takes a few minutes to establish the connection between the working vehicle's battery and the dead battery, and then a few more minutes for the dead battery to receive enough charge to start the engine. However, if the dead battery is severely depleted or damaged, it may take longer, or it might not work at all. It's essential to follow safety precautions and ensure proper connections when jump-starting a vehicle.