TDS (Total Dissolved Solids) describes the concentration of dissolved substances in brewed coffee. For coffee, the value is usually expressed as a percentage and determined with a suitable coffee refractometer.
TDS is primarily a measure of the strength or concentration of the beverage. It can help compare brewing recipes and make changes in a workflow measurable. However, it is not a standalone measure of quality or taste: two coffees with the same TDS value can still taste distinctly different.
TDS and extraction yield are not the same
TDS describes the concentration of dissolved substances in the finished beverage. Extraction yield, by contrast, describes what proportion of the dry coffee dose has been transferred into the beverage as dissolved material.
- TDS: concentration or strength of the beverage
- Extraction yield: proportion of soluble material extracted from the ground coffee
The two measurements are related to factors such as the recipe, beverage mass and dry coffee dose. A TDS value should therefore always be interpreted in the context of the brewing recipe.
Which TDS values are useful?
There is no universal TDS value that can be described as “perfect” regardless of the coffee, roast, brewing method and desired sensory profile.
Filter coffee
As a technical reference range, the Specialty Coffee Association uses, under defined test conditions for the certification of certain filter coffee brewers, a beverage concentration of 1.15 to 1.45% and an extraction yield of 18 to 22%. These figures are a standardized testing range, not a guarantee that every coffee will taste best within it.
More information about current standards is available on the Specialty Coffee Association standards page.
Espresso
Because espresso uses a much more concentrated brewing ratio, its TDS values are considerably higher than those of filter coffee. A single target value is of limited use, however, because recipe, beverage mass, roast, basket, machine and desired profile can vary substantially.
In practice, it is more useful to compare TDS within a clearly defined recipe than to pursue one universal target for espresso.
Which factors influence TDS?
The measured TDS value results from the interaction of several variables, including:
- brew ratio, or the relationship between coffee and water or beverage mass
- grind size and particle distribution
- contact time
- water temperature
- brewing method and flow conditions
- coffee, roast level and solubility
These factors do not act independently. Statements such as “finer always means higher TDS” or “hotter automatically means better extraction” are therefore too simplistic.
Do not confuse coffee TDS with water TDS
The term TDS is used for both brewed coffee and water, but the measurement methods and what the results tell you are different.
For brewed coffee, the concentration of dissolved coffee material is typically determined refractometrically. For water, many so-called TDS meters work from electrical conductivity and estimate the concentration of dissolved ions.
A water TDS value alone does not show which minerals are present. Two water samples with the same TDS value can therefore have different compositions and behave differently in coffee preparation.
For more detail, see our article Water quality and its influence on coffee quality.
Measuring TDS correctly
For brewed coffee, a coffee refractometer is the appropriate tool. Conductivity or TDS meters are useful for water analysis, but they answer a different question.
Coffee refractometer
A suitable refractometer can be used to determine the concentration of brewed coffee. For comparable results, a clean sample, correct use of the instrument and a consistent measurement procedure are important.
Our shop offers the Coffee refractometer for baristas for TDS and extraction analysis.
Water TDS and conductivity
For a quick check of water TDS and conductivity, the Digital 4-in-1 TDS Meter HA 2 is one available option. Such a device does not replace a detailed analysis of the actual mineral composition of the water.
How TDS helps when dialing in a recipe
TDS is particularly useful when several shots or brews are compared under otherwise similar conditions. If grind size, brew ratio or contact time changes, for example, the measurement can show how the concentration of the beverage has changed.
The measurement should always be combined with sensory evaluation. A repeatable reading is useful, but the decisive question remains how the coffee tastes in the particular recipe.
FAQ: TDS in coffee
Is a higher TDS value automatically better?
No. A higher TDS value initially means only that the beverage contains a higher concentration of dissolved material. Whether that is desirable depends on the coffee and the recipe.
Which is more important: TDS or extraction yield?
They answer different questions and complement each other. TDS describes beverage concentration, while extraction yield describes the proportion of material dissolved from the dry coffee dose.
Can a water TDS meter measure coffee TDS?
For a reliable coffee TDS measurement, a refractometer designed for this purpose should be used. Conductivity-based water TDS meters are intended for water analysis.
Do I need to measure TDS to make good coffee?
No. TDS is an additional tool for analysis, comparison and repeatable work. It does not replace sensory evaluation.
Conclusion
TDS makes the concentration of a coffee beverage measurable and can help compare recipes systematically. Its value lies not in replacing taste with a single number, but in combining measurement data with recipe information and sensory evaluation.
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