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tags: [] - coffee/brewing - coffee/science aliases: - Measuring coffee extraction - TDS and extraction yield measurement - Coffee refractometer use

Extraction Measurement

Tags: #coffee/brewing #coffee/science Aliases: Measuring coffee extraction, TDS and extraction yield measurement, Coffee refractometer use Related: Coffee Extraction Fundamentals MOC | Extraction Yield | Extraction Efficiency | TDS | Refractometer Status: 🌱 Stub

Overview

Extraction measurement converts subjective tasting impressions into repeatable, documented numbers by quantifying the two primary brew metrics: Total Dissolved Solids (TDS) and Extraction Yield (EY). Neither metric is required to brew well, but both are essential for systematic recipe development, quality control, and inter-session consistency.

Key Metrics

Total Dissolved Solids (TDS)

TDS measures the concentration of dissolved coffee compounds in the brew — the effective strength of the cup. It is expressed as a percentage of the brew weight.

Typical TDS targets by method:

Method TDS %
Espresso 8–12%
Filter / pour-over 1.15–1.45%
French press 1.20–1.50%
Cold brew (concentrate) Variable (typically 3–8%)

Extraction Yield (EY)

EY measures what percentage of the coffee's dry mass was dissolved into the cup — the completeness of extraction.

Formula: EY (%) = (TDS × Beverage weight) ÷ Coffee dose × 100

Example: 20 g dose, 300 g beverage, 1.28% TDS → EY = (1.28 × 300) ÷ 20 = 19.2%

SCA target range: 18–22% for most brew methods.

Measurement Tools

Refractometers measure TDS by passing light through a brew sample and measuring the refractive index change. Digital refractometers (VST Coffee Tools is the industry standard) are more accurate than optical models. The refractometer prism must be calibrated to zero with distilled water before use. Brew samples must be cooled to room temperature before measurement, as heat distorts readings.

Precision scales (0.1 g resolution minimum) are required to measure dose and brew weight accurately. Combined scale-and-timer units are common in pour-over brewing.

Measurement Procedure

  1. Brew using precisely documented parameters
  2. Collect a representative sample (stir to homogenise before sampling)
  3. Cool sample to room temperature
  4. Place a drop on the calibrated refractometer prism
  5. Read TDS percentage
  6. Calculate EY using the formula above

Key Facts

  • TDS measures brew concentration (strength); EY measures extraction completeness (how much of the coffee has dissolved)
  • SCA optimal EY range: 18–22% for most methods; TDS targets vary significantly by brew method
  • Digital refractometers (VST) are the industry standard; must be calibrated with distilled water and used on cooled samples
  • EY = (TDS × beverage weight) ÷ dose × 100

References

Changelog

Date Change
2026-05-03 Compliance review: replaced malformed frontmatter tags: [extraction, measurement, TDS, refractometer, brewing-science] and removed date_created:/updated: non-standard fields; added metadata block; removed navigation arrow ← Part of [Coffee Extraction Fundamentals MOC](../maps-of-content/coffee-extraction-fundamentals-moc.md); removed dangling **Tags:** at end; added Overview, TDS/EY tables, measurement procedure, all required sections, copyright

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