How to pronounce “eighths” in English

The Martian environment is very harsh with the thin atmosphere, three-eighths G, solar radiation, all these things—building suits that can handle that when you're doing these

For example, the radius of an animal's aorta should scale with its mass to the three-eighths or .375.

for example, this one, the quarter quarter, two-eighths quarter-- a particular onset stability by combining all of the ratios and getting something stable.