Airlines charge as much as $100 for a bag that's just ounces over their limits (usually 50 pounds). A luggage scale will pay for itself many times over the first time you avoid those fees.
This scale has a nice 2-handed grip for easy lifting, and an easy-to-read digital display screen. It's small and light weight, so it adds almost nothing to your carry-on (and you will want to toss it into your carry-on for the return flight). It also gets 5 stars from those who have used it - simply the best product on the market for the price!