So we all know that Luffy ate the Gomu Gomu no Mi Devil fruit and I found in the Gomu Gomu no Mi's wiki page that Luffy is able to stretch a length of 72 Gomu Gomu's. So is there any real way to turn 72 Gomu Gomu's into a real world measurement of length?
No there is not. At the SBS of chapter 30, Oda was asked how far Luffy's arm can stretch. He humorously replied
O: Pretty far. Right now it can stretch about 72 Gomu Gomus. Luffy was telling me before how he wanted to try hard and reach 100 Gomu Gomus.
Later at the SBS of chapter 47, he was asked how many liters go into 1 Gomu Gomu and he replied
O: Oh, you've come again! Gaimon's son. In "1 Gomu Gomu" there are "10 Fairy Tale Gomu Gomus". And in each "Fairy Tale Gomu Gomu" there are "10 Funky Gomu Gomus" so, in other words Luffy's arm can stretch around 7200 Funky Gomu Gomus. Understood?
When reading the SBS's you will see more of these funny replies and measurements come up, but you will never get a real world comparison.
The problem is that Luffy moves around too much. Oda was never able to measure how long one Gomu Gomu is. We will just have to trust Luffy's word, that it really is 72 Gomu Gomus and we can only imagine the real world distance.