OK, let's see, everyone added together? Like, standing on shoulders?
If the average man is 1.7m and the average woman 1.6m, the average person is 1.65m
With 6 billion adults, this gives us 9,900,000,000m
Children are tougher, but let's try. 2 billion of them, and newborns average 0.5m. So, averaging between adult height and 0.5m gives us 1.075m. Multiplying this by 2 billion gives us 2,150,000,000m
Adding together, we get 12,050,000,000m.
And that's how tall everyone is. Ish.
Unless they're just standing next to each other. In which case, a little bit less.
I'm tired, it's probably full of errors, it doesn't matter