Compare flights by cost per mile.
Cost per mile flown is the only way to compare fares across routes of different lengths, and the benchmarks differ sharply by cabin: economy typically runs around 13 cents a mile, premium economy about 22, and business 40 or more. Long-haul flights are almost always cheaper per mile than short-haul, because the fixed costs of a departure — crew, slots, turnaround, taxi and climb — are spread across far more distance. The second half of the calculation nets off the miles you earn, valued at whatever you can actually redeem them for, which on a mileage-rich fare can shift the effective cost by several percent.
Cost per mile
Cents per mile = ticket price x 100 / miles flown
Net of rewards
Net cents per mile = (price - earned miles x value per mile) x 100 / miles flown
Because a large share of the cost of any flight is incurred on the ground and in the climb, regardless of distance — crew time, airport slots, turnaround, fuel burned getting to altitude. Spreading that across 300 miles instead of 4000 makes the per-mile figure several times higher.
For most major programmes, 1.0 to 1.5 cents when redeemed sensibly for flights. Redeeming for merchandise or gift cards usually yields well under 1 cent; premium-cabin redemptions booked well can exceed 2. Use the value you realistically achieve, not the best case in a blog post.