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Espresso Water-to-Coffee Ratio: Characteristics and Golden Ratio Extraction Methods

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Espresso Water-to-Coffee Ratio - To master the espresso extraction golden ratio, you can use a consistent coffee dose (18g as an example) in your practice and experiment with different total coffee weights. Then compare the differences in texture, clarity, and body across various ratios. You need to decide based on personal preference

FrontStreet Coffee has always emphasized that extraction parameters significantly impact a cup of pour-over coffee, and their influence on espresso extraction is even greater. Espresso parameters such as concentration and extraction time are more stringent than pour-over coffee. Even slight deviations can cause exponential changes in the flavor of an espresso shot. Therefore, understanding espresso extraction parameters is truly essential.

Espresso Extraction Parameters

Similar to pour-over coffee extraction parameters, espresso places even greater emphasis on extraction parameters. Below, FrontStreet Coffee will explain and analyze coffee dose, brew ratio, extraction time, flow rate, extraction pressure, and extraction temperature.

Coffee Dose

The amount of coffee dose is determined by the capacity of the portafilter basket. Some coffee machine manufacturers offer double basket capacities in various specifications such as 16g, 18g, 20g, 22g, and more. These specifications are recommended capacities with a maximum filling error of less than 1g. For example, when using an 18g basket, the reasonable dose range can be 17-19g.

FrontStreet Coffee does not recommend using significantly less or much more coffee than the basket capacity. The amount of coffee affects the density of the coffee puck. With the same tamping pressure, too little coffee will result in a looser puck, leading to faster flow rates and under-extraction. Conversely, higher density results in slower flow rates and may even make it difficult to extract coffee liquid.

Brew Ratio

Espresso uses a ratio of coffee grounds to extracted espresso liquid, because you cannot calculate how much water was used for extraction. Of course, some newer coffee machines install a meter at the water inlet to display water volume. The traditional extraction ratio was based on single-shot standards, extracting 25-30ml of espresso liquid from 7-8g of coffee grounds. The former is a weight unit, while the latter is a volume unit. These are only equivalent when density is consistent, but as we know, extracted espresso contains golden crema, and the thickness of this crema layer depends on the coffee's roast level and freshness. Therefore, using this measurement method can cause inconsistent results.

This led to the emergence of the weight-to-weight ratio (coffee grounds weight to liquid weight). This typically ranges between 1:1.5 to 1:2.5, with 1:2 being the most commonly used ratio, such as extracting 40g of coffee liquid from 20g of coffee grounds. The ratio is influenced by two factors: the amount of coffee and the amount of water. A lower ratio results in very rich, thick coffee that can easily develop bitterness from over-extraction. Conversely, a higher ratio produces thin, bland coffee with sharp acidity from under-extraction.

Extraction Time

Time refers to the entire extraction period from when the portafilter is locked in and the extraction button is pressed until the extraction is complete. Factors affecting extraction time include grind size and ratio. The ratio is easy to understand: higher ratios require more extraction water, naturally taking longer time. Grind size affects the coarseness of coffee grounds, which directly impacts the density of the coffee puck. Finer coffee grounds create a denser puck after tamping, making it difficult for water to pass through, extending extraction time and easily leading to over-extraction. Generally, extracting a shot of espresso takes approximately 20-30 seconds.

Flow Rate

Flow rate is the speed at which coffee liquid flows. The ultimate goal of our extraction parameters is actually to achieve a specific flow rate. For normal espresso, the first drop of coffee liquid should appear around the fifth second after pressing the extraction button, with subsequent flow being relatively uniform. The speed of flow directly reflects whether the grind size and ratio are appropriate. If the first drop appears after more than 10 seconds (excluding pre-infusion), the coffee might be ground too fine or tamped too firmly. If the flow is too fast or shows gushing, the coffee might be ground too coarse or channeling may have occurred.

Extraction Pressure

Generally, semi-automatic coffee machines operate at approximately 9bar of extraction pressure, which is determined by the machine's performance. Some modern coffee machines now feature variable pressure extraction. Lower pressure results in lower extraction efficiency, while higher pressure yields higher extraction efficiency.

Extraction Temperature

The water temperature for espresso extraction typically ranges between 90 to 94 degrees Celsius. Water that is too high in temperature can easily lead to over-extraction, causing bitter coffee flavors. Water that is too low can result in under-extraction, leading to sharp acidity in coffee.

Important Details for Making Espresso

The process of making espresso can generally be divided into several major parts: weighing coffee, distributing grounds, tamping, machine extraction, and cleaning. FrontStreet Coffee has previously mentioned that distributing and tamping are crucial for a good espresso. While other factors have secondary impact on a shot, they still have effects that cannot be ignored.

Weighing Coffee

There are two points to consider when weighing coffee: the influence of residual grounds and the accuracy of the dose. Carefully observe your espresso grinder - whether it's a hopper model or doserless model - there is a channel between the burrs and the dispensing outlet that accumulates previously ground coffee. If too much time has passed since the last grinding, the coffee in this channel will have lost most of its flavor. At this point, you should use a tool to clear the coffee from the channel, or start the grinder to let subsequent coffee grounds push out the previous grounds and discard them before collecting fresh grounds.

Taking the Fiorenzato 900N grinder used by FrontStreet Coffee as an example, the residual coffee in its channel can weigh up to 2 grams. If we consider a double shot with 20g of coffee grounds, this accounts for one-tenth of the total dose, showing how significant this impact can be.

Next is the issue of weighing accuracy. Using the Fiorenzato 900N as an example again, FrontStreet Coffee uses the non-dosing version, which requires a highly sensitive electronic scale for assistance. To ensure precise and consistent results, each extraction should involve weighing the coffee grounds. FrontStreet Coffee recommends keeping the maximum error within ±0.1 grams.

If you're using a dosing grinder, please don't overlook this issue either. Most dosing grinders currently use timing-based principles (with some exceptions), and timing creates problems such as inconsistent rotation speeds, varying bean hopper pressure, and differences in coffee bean size and density, all of which can cause discrepancies in grinding amounts.

Inconsistent Rotation Speeds

Inconsistent rotation speeds are related to voltage. Domestic voltage fluctuates around 220V with a ±10V tolerance. Higher voltage results in faster speeds, while lower voltage leads to slower rotation.

Varying Bean Hopper Pressure

Different amounts of coffee beans stored in the hopper during each grinding session can cause inconsistent hopper pressure. When hopper pressure is unstable, it affects the consistency of the dispensing amount.

Varying Coffee Bean Size and Density

Coffee bean blends consist of different varieties with differences in size and hardness. The varying proportions of these varieties in each grinding session can also lead to differences in ground amounts.

Extraction Workflow and Cleanliness

The extraction process should be methodical, from grinding to collecting grounds, distributing, tamping, then locking the portafilter and pressing the extraction button. Theoretically, this sequence of actions should be continuous without interruption. Therefore, before grinding, you should clearly think about what comes next and what hasn't been prepared yet. If you're still unfamiliar with the operations, you can practice multiple times until you become proficient.

Develop good cleaning habits. First, a clean environment provides a comfortable feeling. Second, cleaning key components affects the quality of the next cup of coffee, such as the residual grounds in the grinder mentioned above. Additionally, residual grounds on distribution tools and tampers should be cleaned. Ensure that tools in direct contact with coffee grounds - such as distributors, portafilters, and baskets - remain dry (in plain terms, no water residue on these tools), and rinse and clean them after each use.

After completing an espresso extraction, remember to clean the portafilter and group head immediately afterward (no matter how busy you are). These seemingly unimportant coffee residues can affect the quality of the next espresso shot.