Please also note that, according to Wikipedia, the Egyptian cubit rods range from 44.4 to 52.92 cm in length. That is a rather variable constant.
The actual length of a cubit varied between different ancient groups of people. Here are some samples from Egypt, Babylon, and ancient Israel:
Hebrew 17.5 in
Egyptian 17.6 in
Babylonian Long 19.8 in
Hebrew Long est. 20.4 in
Egyptian Long 20.6 in
Guess which one Moses was referring to?
https://arkencounter.com/noahs-ark/cubit/