United Airlines miles are worth 1.3 cents apiece on average when redeemed for flights, according to Insider's valuations. But they can be worth less or more depending on how you redeem them. It's possible to receive a return of as little as 0.3 cents per mile when using them to purchase gift cards or merchandise. And you can achieve a value as high as 7+ cents per mile when you use them for fancy lie-flat international business class seats.