According to Genesis, the Ark’s width-to-height ratio was 5:3.
Genesis 6:15 gives the Ark as 300 cubits long, 50 cubits wide, and 30 cubits high. Comparing the width and height produces 50:30, which simplifies to 5:3.
The ratio describes the vessel’s stated proportions, not a modern reconstruction. Because the cubit’s exact length is uncertain, converting the dimensions into meters or feet changes the estimated size but not the ratios between the three measurements.
The Ark’s length-to-width ratio is 6:1, a different comparison that is often quoted in discussions of its shape. The question asks specifically for width divided by height, so 5:3 is the reduced ratio based on Genesis’s measurements.