The ark was the grand part of all the sacred furniture. If we suppose the Jewish cubit was 21 inches, then it will follow that the ark itself was about 52 inches long, and about 30 in breadth and depth.
Related Commentaries of Exodus 25:10
Exodus 25:10
10 And they shall make an ark of shittim wood: two cubits and a half shall be the length thereof, and a cubit and a half the breadth thereof, and a cubit and a half the height thereof.