I attended a coffee class on Nov 7, 2026, and this is what I learned.

Espresso Made Simple

The formula for making an espresso can be simplifed thus:

Forcing hot water at T °C under a pressure of P bars, through a container (called a basket) of M g of coffee beans ground to a particle size of X mm, for b seconds to fill a cup of V ml of the drink (including crema - the brown bubble foam).

The specifications are:

• T : 92 to 96 °C
• P : 9 to 10 bars
• M : 18 g
• X : ??
• b : 20 to 30 seconds
• V : 30 cc

The task is reduced to solving for X as it is the only parameter that cannot be easily or practically determined without expensive equipment and effort. All connsumer-grade grinding machines use their own relative coarse/fine scale.

You solve the equation using an espresso machine, by titrating the granularity X of the ground coffee power until you achieve 30 ml of coffee while maintaining all the other numbers constant.