Espresso Extraction Time

Espresso shot time and brew ratio

The brew ratio takes the mass of liquid espresso and divides it by the mass of dry coffee (or by volume, as a first approximation): ratio = ml / g. Baristas work back from that to estimate a target shot time. This calculator runs t = 25 + (ratio − 2) · 5, clamped to the 20–40 s window, which sits close to common SCA guidance for traditional espresso. Take 18 g of ground coffee pulling 36 ml: that's a 2.0:1 ratio and roughly 25 s, about as textbook a normale as you'll get.

A ristretto (ratio around 1.5:1) tends to pull faster and taste denser. A lungo (ratio around 3:1) pulls for longer and comes out more diluted and bitter. Grind size, dose, tamping pressure and water temperature all feed into the extraction too, so treat the time/ratio relation as a starting point rather than a guarantee.

Applications

• Bar calibration, when you change the dose or basket size and need a new target time.
• Recipe documentation, recording standard ratios for cafés and competitions (WBC).
• Home espresso, where you dial in the grind by nudging the expected shot time for your chosen ratio.

FAQ

Should I weigh in grams or measure in ml? Weighing the output in grams is the more accurate route, since crema density varies, but ml works as a reasonable proxy when you're moving at café speed.

Why clamp between 20 and 40 s? Step outside that window and the shot is usually either underextracted and sour, or overextracted and bitter, whatever the ratio happens to be.

Is the relation linear in reality? Not really. Extraction kinetics are non-linear. Think of the formula as a practical estimate that helps you dial in, not as a physics model.