9 bar standard

The traditional brewing pressure for espresso — 9 bar (about 130 psi) at the puck. Established by Achille Gaggia's lever machines in the 1940s and adopted as a global standard.

Why it matters — 9 bar is the design target for most espresso baskets and groups. The brew dynamics — how the puck compresses, how water flows through it, how crema forms — are calibrated around this pressure.

Good to know

• Many machines ship with the OPV set higher (10–11 bar) for headroom. Dialling down to 9 bar improves most shots.
• Modern flow-profiling and pressure-profiling machines vary pressure during the shot, often pulling at 6–9 bar during pre-infusion and ramping or holding 9 bar through the main shot.