On a beer CO₂ regulator, the low-pressure gauge is used to read the serving or dispensing pressure — the pressure of CO₂ being delivered from the regulator into your keg.

• It usually measures in the range of 0–60 psi (sometimes up to 100 psi, depending on the regulator).

• Typical serving pressure for beer is around 8–15 psi, depending on beer style, line length, and carbonation level.

• This gauge tells you what pressure your keg is being held at, which controls carbonation and pouring speed.

By contrast, the high-pressure gauge reads the pressure inside the CO₂ cylinder (normally 800–1000 psi when full, depending on temperature).