Different sources regarding the height of the giants discussed by the torah.
Rashi (Zvachim) says that Og didn’t die during the mabul because he stood next to the teivah and he was too tall to drown. This implies that he was taller than even the mountains which were covered by water.
We also find the description of the Giants given by the miraglim that “we were like grasshoppers in their eyes”. There are several interpretations of this but according to those who understand this literally (e.g. the Gra) this fits with Rashi’s pshat
Pirkei Drabi Eliezer says that the teivah had a ladder on the outside. Og survived the mabul by sitting on one
of the rungs. According to this he was much smaller.
The pasuk says that Og’s bed was 9×4 armlengths according to the armlength/amah of “ISH” (a man). An amah is between 18-24 inches. This would make Og about 13.5-18 feet tall.
Rashi learns that the “ISH” in this pasuk means Og himself and therefore you cant use this pasuk as proof of his height.
The Ibn Ezra quoted above says that this would require Og to have a greatly misshaped body if his arms were only a ninth of his height and therefore he learns that the armlength used above to measure is the same one that we use.
According to what was mentioned in the above post that a giant would require large legs to support his body, it could be according to Rashi that the pasuk is telling you exactly that, that he was so misformed because of his great size.
The Rashbam has a different beautiful approach that the reason that the pasuk describes his bed is because it is giving us his dimensions as a baby. “His cradle was 9×4 amos according to the amah of an “ish” – full grown person.” according to this he was much larger as an adult.
The pasuk in Nach that describes Golias says that he was a descendant of the giants and he was 6 and a half amos tall (10-13 feet). This sounds more like those that argue with rashi’s pshat but it could be that this was after many generations of mixed-breeding so he wasn’t so big.