Espresso dose calculator: dose, ratio and yield in one line of math

An espresso dose calculator solves one equation three ways: yield = dose x ratio. Put in 18g of dry coffee at a 1:2 ratio and you are pulling to 36g of liquid espresso, which the National Coffee Association gives as the reference recipe, with 20 to 30 seconds of contact between coffee and water (NCA). Know any two of dose, ratio and yield and the third is fixed. That is the whole tool.

What the three numbers mean

Dose is the dry ground coffee in the basket, weighed before you tamp. Yield is the liquid espresso in the cup, weighed on a scale under the cup, not read off the side of a shot glass. Ratio is yield divided by dose, written as 1:x. The NCA states it plainly: 1 gram of dry coffee to 2 grams of brewed espresso, where the 1 is the weight of the grounds and the 2 is the weight of the liquid extracted.

Every number is a weight. Volume markings on a portafilter spout or a double shot glass measure crema as much as liquid, and crema volume changes with roast date, so they cannot give you a ratio.

Yield table: dose x ratio

Multiplication only. The 1:2 column is the ratio published by the NCA; 1:1.5 and 1:2.5 are the tighter and longer ends people dial toward, and are shown as arithmetic rather than as published recommendations.

Which dose is yours

Dose is set by your basket, not by a universal number. Breville, for example, publishes an ideal dose of 18g for the Barista Express with its 54mm portafilter and 9 bar extraction (Breville). Another machine with a different basket has a different rating, and it is printed in the manual that came with it. Overfill a basket and the puck presses into the shower screen; underfill it and the water carves a channel through a shallow bed. Both show up as a shot that runs to weight at the wrong time.

Once dose is fixed by the basket, ratio is the dial you actually turn, and grind is what makes the shot hit that ratio inside the 20 to 30 second window.

The mistake: chasing time instead of weight

Time is a diagnostic, not a target. If 18g in and 36g out takes 18 seconds, the fix is a finer grind, not stopping the shot early at 30g. If the same recipe takes 45 seconds, the fix is coarser, not letting it run to 36g however long it takes. Set dose and yield first, then move grind until the clock lands in range. That is the order the calculator is built around, and it is the order the dial-in cheat sheet uses.

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None of this works without weighing the shot. A scale that fits under the cup and starts a timer when the first drop lands is the one accessory that makes dose and yield real numbers: search espresso scales with timers on Amazon.

Related reading

FAQ

How do I calculate espresso yield? Multiply dose by the ratio. An 18g dose at 1:2 is 36g of liquid espresso in the cup, weighed on a scale.

What dose should I use for a double shot? Whatever your basket is rated for. Breville publishes 18g as the ideal dose for the Barista Express; your machine's manual gives its own figure.

How long should the shot take? The NCA gives 20 to 30 seconds of contact between coffee and water. If your recipe finishes outside that window, change grind size rather than changing the dose or stopping the shot short.

Sources: the 1:2 espresso ratio (1 gram of dry coffee to 2 grams of brewed espresso) and the 20 to 30 second brewing time are published by the National Coffee Association at aboutcoffee.org. The 18g ideal dose, 54mm portafilter and 9 bar extraction figures are Breville's own published specifications for the Barista Express BES870 (breville.com). Both fetched and cached 2026-08-18. Every yield in the table is dose multiplied by ratio.