If humans had wings how long would they have to be?

If humans had wings, their length would likely need to be proportional to their body size and weight to support flight. Based on the wing-loading ratio observed in birds, wings could be around 10 to 12 feet long for an average adult human, allowing for sufficient lift and maneuverability. This is speculative, of course, as it would depend on various factors like muscle strength and wing structure.