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tags: [] - coffee/roasting - coffee/roasting/equipment aliases: - Agtron Scale - Agtron Number - Roast Colour Scale

Agtron Scale

Tags: #coffee/roasting #coffee/roasting/equipment Aliases: Agtron Scale, Agtron Number, Roast Colour Scale Related: Roasting MOC | Roast Level | Roast Development | Colour Analysis Status: ✅ Complete

Overview

The Agtron scale is a standardised numerical colour scale used to measure and communicate coffee roast level. Higher Agtron numbers indicate lighter roasts; lower numbers indicate darker roasts. Values are produced by a spectrophotometer — commonly called an Agtron analyser — that measures the amount of near-infrared light reflected from roasted coffee beans or ground coffee. The scale enables objective, repeatable roast description, replacing subjective labels such as "light", "medium", or "dark" with a reproducible measurement.

How It Works

An Agtron analyser directs infrared light at a coffee sample and measures the reflected light intensity. Lightly roasted coffee reflects more light (higher number); darkly roasted coffee absorbs more light and reflects less (lower number). Values typically run from approximately 25 (very dark) to 95 (very light).

Measurements can be taken on: - Whole beans — provides a surface colour reading - Ground coffee — provides a reading that averages colour throughout the bean, generally giving a more accurate internal roast assessment

Ground readings typically yield a higher (lighter) number than whole-bean readings from the same sample, because the exterior of the bean roasts faster than the interior.

Typical Roast Ranges

Roast Level Typical Agtron Range Cup Character
Very light (Nordic, white) 80–95 Highest acidity; prominent origin character; grain-like
Light 70–80 Bright acidity; floral and fruit notes; light body
Medium-light 60–70 Balanced brightness and sweetness; emerging body
Medium 50–60 Balance of acidity, sweetness, and body; developed sugars
Medium-dark 40–50 Reduced acidity; caramel and chocolate notes; heavier body
Dark 25–40 Low acidity; roasty, smoky, bitter notes dominant

Exact cutoffs vary by roastery and convention. The SCA does not mandate fixed range definitions.

SCA and Industry Standards

The Specialty Coffee Association uses Agtron values as part of its roast colour standards. The Agtron E20CP analyser can be calibrated to two industry scales:

  • Gourmet scale: Used primarily for specialty coffee applications
  • Commercial scale: Used for commodity and commodity-adjacent coffee; values read approximately 10–15 points lower than the Gourmet scale at the same roast level

Other instruments — including the Lighttells CM-100, the Javalytics, and colour-analysing software tools — are often calibrated to report Agtron-equivalent numbers, allowing cross-tool consistency within a facility.

Practical Applications

Roast consistency: Targeting a specific Agtron number for a given coffee allows roasters to reproduce and match roast batches over time, regardless of batch size or operator.

Quality control: Comparing measured Agtron values against target values identifies roast deviations before coffee reaches the cupping table.

Recipe development: Specifying Agtron number in recipe documentation allows collaborators, wholesale partners, and roasters to align on a target roast profile.

Sensory benchmarking: Understanding the relationship between Agtron number and cup character helps roasters predict and communicate flavour outcomes to buyers and customers.

Limitations

  • Agtron measures colour only, not total roast development or flavour complexity — two batches with the same Agtron number may taste different if their roast profiles (rate of rise, development time ratio) differed
  • Whole-bean and ground readings from the same sample are not directly comparable
  • Different instrument brands and calibration scales require documented conversion to ensure meaningful comparison

Key Facts

  • The Agtron scale measures roast level numerically; higher numbers = lighter roasts, lower numbers = darker roasts
  • Values typically range from 25 (very dark) to 95 (very light)
  • Ground coffee readings typically yield higher values than whole-bean readings from the same sample
  • The SCA recognises two calibration scales: Gourmet and Commercial (the Commercial scale reads approximately 10–15 points lower)
  • The scale enables objective, repeatable roast communication but does not capture all dimensions of roast quality

References

Changelog

Date Change
2026-04-29 Compliance review: complete rewrite — added frontmatter, metadata block, all required sections; removed inline AI citation links and raw URL list; fixed American English (color → colour, flavors → flavours); applied Australian English; added copyright notice

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