Flying with Frontier Airlines personal item size restrictions means you must pack strategically to avoid extra fees. The airline only allows one free personal bag size Frontier, with strict dimensions for personal item Frontier set at 18 x 14 x 8 inches. If your bag is too large, you could end up paying hefty carry-on fees. Choosing the right Frontier personal bag size and using space-saving packing techniques can help you fit everything you need into your free bag. Follow these expert tips to travel light and stay within the airline’s baggage policy.