Espresso Pump Pressure & Flow Calculator

Nine bar is a convention, not a law of flavour. Flow through a puck is messy: grind size, dose, and channeling all beat the gauge. This sketch treats flow as rising with pressure and falling with dose so you can see why a choked 22 g basket at 9 bar runs slower than an 18 g one. Then you still have to taste.

Inputs

Units

Results

Estimated flow: 1.30ml/s
Time for a 1:2: 27.7s

Recommended gear

Espresso machine
A gauge you can actually read during the shot is worth more than this sketch. OPV-adjustable pumps live here.
Typical range: $400–$2,500
Precision espresso basket
Even holes so flow is the puck, not two wild jets. Channeling laughs at bar numbers.
Typical range: $20–$40
WDT tool
If flow is double the estimate, fluff the dose. Needles before pressure profiling.
Typical range: $15–$50

Calculation method

A reference 18 g puck at 9 bar is treated as about 1.3 ml/s (a 36 g / ~28 s shot). Flow scales up with pressure and down with dose. Shot time for a 1:2 is twice the dose (as ml) divided by that flow. 6 bar at the same dose runs slower in this model; 22 g at 9 bar also slows. Real pucks are not linear orifices.

Exact formula

flowMlS = 1.3 × (pressureBar / 9) / (doseG / 18). shotTimeS = (2 × doseG) / flowMlS for a 1:2. Limits: Pump curves, gicleur, puck porosity and channeling omitted; ml ≈ g for water, not crema.

OPV versus pump max

A rotary at 9 bar with a good puck is not a vibratory slamming the relief valve. If the gauge bounces, the number you typed is a wish.

Frequently asked questions

Should I brew at 6 bar?

Some light roasts like it. This page will show slower flow at the same dose — you still grind to taste, not to the sketch.

ml/s versus g/s?

For water they are close. Crema makes volume lie; weigh yield as in the dosing calculator.

Preinfusion?

Not modelled. Low-pressure preinfusion changes how the puck wets, then you may ramp to 9 bar. Use your machine’s program, not this average.

Disclaimer — no professional advice, no liability

This is not a profiling recommendation and not your machine’s flowmeter. A gushing shot at 9 bar is a puck failure. Fix distribution before you lower pressure to ‘fix’ flow.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a cupping score, a water lab report or a roasting profile, and they do not constitute professional barista, roasting, food-safety or medical advice.

Results can be wrong, incomplete or inapplicable to your grinder, brewer, beans, water or use case. You must independently verify every figure, assume all risk, and confirm on a test brew before you scale a recipe, descale a machine or change caffeine habits. Hot water, steam and espresso equipment can scald; caffeine calculators are not a substitute for medical care.

To the fullest extent permitted by applicable law, the site operator, authors, contributors and affiliates disclaim all warranties, express or implied, and accept no liability for any direct, indirect, incidental, special, consequential or punitive damages, or for property damage, burnt shots, injury, death, business interruption or financial loss, arising out of or related to the use of, or reliance on, these tools or their outputs.

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Espresso Pump Pressure & Flow Calculator

Inputs

Results

Recommended gear

Calculation method

Exact formula

OPV versus pump max

Frequently asked questions

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