Spirit Airlines (NK) will charge the following for bags that are greater than the standard 50 pounds or 23 kilograms: 41 to 50 pounds or 18 to 23 kilograms: $30.00 USD extra per bag. 51 to 70 pounds or 23 to 32 kilograms: $55.00 USD extra per bag. 71 to 100 pounds or 32 to 45 kilograms: $100.00 USD extra per bag.