What is the psi value corresponding to 1 atmosphere of pressure?

• A. 9.8 psi
• B. 33 psi
• C. 14.7 psi (0.445 psi per fsw)
• D. 7.2 psi

Answer: (C)

One atmosphere is the standard atmospheric pressure at sea level, defined as about 101.3 kPa, which is exactly 14.7 pounds per square inch. This value is the reference point for absolute pressure. In diving terms, you also see the idea that seawater adds pressure as you go deeper, roughly 0.445 psi for each additional foot of depth, so 33 feet of seawater adds about 14.7 psi. That’s why the psi value for one atmosphere is 14.7 psi, with the note about 0.445 psi per fsw as a helpful depth-to-pressure conversion. The other numbers don’t match the standard atmospheric pressure at the surface.