TDS in coffee shows the concentration of dissolved solids in the brew. You will also see the same abbreviation used for water, but there the figure describes its mineral content. We explain how to read both measurements and how TDS differs from extraction.
What does TDS mean in water?
Water TDS describes the total amount of substances dissolved in it, including minerals. The figure on a label or a meter does not, however, tell you exactly which substances they are or in what proportions they occur.
A typical TDS meter usually measures the electrical conductivity of water and converts it into an estimated TDS value. The conversion depends on the water’s composition, so this kind of meter is no substitute for a full chemical analysis. Two waters with similar TDS can differ in composition.
What does TDS in coffee mean?
The TDS of a brew tells you what share of its mass is dissolved coffee solids. If a coffee has 1.25% TDS, that means roughly 1.25 g of dissolved solids per 100 g of brew.
To measure coffee TDS, you use a coffee refractometer. The device measures how light bends as it passes through the sample, then converts the reading into concentration. So TDS describes strength, that is, the concentration of the brew. It is not a direct measure of quality. Two coffees with the same reading can taste different.
| What are you measuring? | What does the result mean? | Usually expressed as |
|---|---|---|
| Water TDS | Total amount of substances dissolved in the water | mg/l or ppm |
| Coffee TDS | Concentration of dissolved coffee solids in the brew | % |
TDS vs extraction: not the same thing
TDS tells you how concentrated the brew is. Extraction tells you what percentage of the dry coffee’s mass has passed into the drink. The two values are related, but they cannot be used interchangeably.
If you know the TDS, the weight of the finished brew and the coffee dose, you can estimate extraction:
extraction (%) = TDS (%) × brew weight ÷ dry coffee weight
Example: from 18 g of coffee you make 280 g of brew at 1.25% TDS.
1.25 × 280 ÷ 18 ≈ 19.4%
This calculation helps you compare recipes, but it does not fully predict flavour. Research described by the SCA shows that both TDS and extraction affect how a brew is perceived, and that individual flavour attributes do not all change in the same way.
What is a good TDS for filter coffee?
The classic SCA brewing chart gives filter coffee a reference range of 1.15-1.35% TDS and 18-22% extraction. It is a useful range to start testing from, not a guarantee that the brew will suit everyone. The SCA itself points out that the classic chart simplifies the relationship between measurements and sensory perception.
If the coffee is too strong or too weak, start by changing the coffee-to-water ratio. When it tastes unpleasantly sour, bitter or flat, a TDS reading alone is not enough to point to the cause. Check the grind, brew time and pouring technique as well.
How to measure coffee TDS
Use a refractometer designed for coffee and follow the manufacturer’s instructions. As a rule, the sample should be well stirred, filtered to remove fine particles and cooled before measuring. Coffee fines and temperature can both affect the reading. To compare results, follow the same procedure every time.
Sources
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U.S. Geological Survey, Groundwater salinity: Applying the specific conductance and water type proxy: estimating water TDS from conductivity.
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U.S. Environmental Protection Agency, Conductivity: the link between conductivity, dissolved substances and TDS estimates.
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Specialty Coffee Association, Towards a New Brewing Chart: the role of TDS and extraction, and the limitations of the classic brewing chart.
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Specialty Coffee Association, SCA Brewing Chart: the brewing chart and TDS scale.
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Specialty Coffee Association, Manipulating and Measuring a Key Attribute in Drip Brew Coffee: research on how TDS and extraction relate to perceived brew attributes
Frequently asked questions about TDS in coffee
Do water TDS and coffee TDS mean the same thing?
Both abbreviations refer to the total amount of dissolved substances. The values, however, describe different samples: water TDS describes the water, while coffee TDS describes the concentration of coffee solids in the brew.
Does a high TDS mean the coffee is better?
No. A higher TDS means a more concentrated brew. It does not decide its quality or whether a particular person will enjoy it.
Does TDS show how much of the coffee has been extracted?
Not on its own. TDS measures the concentration of the brew. To estimate extraction, you also need the brew weight and the dry coffee dose.
Can a water TDS meter be used to measure coffee?
A typical water TDS meter converts electrical conductivity into an estimated reading. The TDS of brewed coffee is measured with a coffee refractometer. These are different methods, so the results should not be compared directly.
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