Hmm well doing quick research and calculations
Luffy is 174 CM Tall so we need to figure out how many 174 Cm add up to Haralds height. The problem we find ourselves is we don't actually know Haralds height so lets try to figure that out, from Panels alone he looks similar in height as Loki, nearly twice the sizes of other giants, with that being said Loki's exact height hasn't been revealed either, so we gotta do another comparision, Loki's height was compared to Oars, whose height we do have record of oars stands at 219 feet and 10 inches which is the equivalent of 6700.52 CM
So now that we have a baseline for height to work with (Until we get the true numbers) we must now calculate how many times 174 goes into 6700.52 just for the sake of simple math lets just do 6700
6700/174= 38.5057471264 which would round up to 39
So if my calculations are correct approixmately 39 Luffys = 1 Harald