Total Dissolved Solids in Coffee: TDS, Strength, Refractometers, and Extraction Yield
Total dissolved solids (TDS) in brewed coffee is an estimate of the concentration of dissolved coffee material in the beverage. It is usually expressed as a percentage and is one of the main quantitative ways to describe coffee strength.
TDS describes strength, not extraction by itself
A beverage at 1.35% TDS contains roughly 1.35% dissolved coffee solids by mass. Espresso commonly has a much higher TDS because it contains far less water relative to the coffee dose. TDS tells you how concentrated the drink is; it does not directly tell you how much of the dry coffee was extracted.
How TDS is measured
Coffee refractometers estimate TDS from refractive index. The instrument measures how much the beverage bends light and uses a coffee-specific calibration to estimate dissolved-solids concentration. Samples should be mixed, cooled as required by the instrument, and free of excessive bubbles or suspended particles that can distort readings.
TDS and extraction yield
Extraction yield combines beverage mass, TDS, and dry coffee dose. A simplified relationship is:
Extraction yield ≈ beverage mass × TDS ÷ dry coffee dose
For example, if 300 g of brewed coffee measures 1.4% TDS and the dose was 20 g, the estimated extraction yield is about 21%.
High TDS is not automatically better
A stronger beverage can still be under-extracted, over-extracted, bitter, sour, or unbalanced. TDS is useful because it separates concentration from extraction, but sensory evaluation remains essential.
Water TDS is a different use of the same abbreviation
When discussing brewing water, TDS refers to dissolved minerals and ions in the source water. A conductivity meter can estimate that mineral concentration, but it does not reveal which ions are present. Beverage TDS and water TDS should not be confused.
Watch: Measuring TDS and Extraction with a Refractometer
Lance Hedrick’s refractometer comparison includes a useful explanation of coffee TDS, extraction yield, sampling, and measurement best practices before comparing instruments.
For a broader explanation, read our published coffee extraction guide and our espresso scale and ratio guide. More measurement terms are in the glossary.
