tags: [] - coffee/roasting - coffee/roasting/production aliases: - Roast yield - Weight loss in roasting - Roasting weight reduction

Roast Weight Loss¶

Tags: #coffee/roasting #coffee/roasting/production Aliases: Roast yield, Weight loss in roasting, Roasting weight reduction Related: Roasting MOC | Moisture Loss | Density Loss | Roast Profile | Development Phase Status: ✅ Complete

Overview¶

Roast weight loss (also called roast yield or percentage weight loss) is the reduction in batch mass from green bean weight to roasted bean weight, expressed as a percentage of the original green weight. It is one of the most fundamental production metrics in coffee roasting, reflecting the combined loss of water, carbon dioxide, and volatile aromatic compounds during the roast. Roast weight loss increases with roast level and roast duration, and is directly linked to roast cost — lighter roasts retain more mass per kilogram of green coffee purchased, while darker roasts sacrifice more of the green weight to produce the roasted yield. Tracking roast weight loss batch-by-batch is a standard quality control practice that provides diagnostic information about roast consistency.

Components of Roast Weight Loss¶

Total roast weight loss comprises three categories:

Component	Approximate proportion	Release mechanism
Water vapour	~50–70% of total loss	Drying phase (free water); ongoing through roast (bound water)
Carbon dioxide	~20–35% of total loss	Formed by Maillard, caramelisation, and pyrolytic reactions; accumulates in bean and degasses post-roast
Volatile compounds	~5–15% of total loss	Aromatic compounds formed and released during browning and development

The relative proportions shift with roast level: in lighter roasts, moisture loss dominates; in darker roasts, CO₂ formation and volatile compound loss account for proportionally more of the total.

Typical Roast Weight Loss Ranges¶

Roast Level	Typical Weight Loss
Light roast	12–14%
Medium roast	13–16%
Medium-dark	15–18%
Dark (French, Italian)	17–22%+

These figures are approximate and vary by green coffee moisture content, bean density, roaster type, and batch size. High-moisture green coffee loses proportionally more weight in the drying phase than low-moisture green coffee at the same roast level.

Calculating Roast Weight Loss¶

Roast weight loss percentage is calculated as:

Weight loss % = (Green weight − Roasted weight) ÷ Green weight × 100

For example, a batch charged with 10.00 kg green coffee that yields 8.50 kg roasted coffee: (10.00 − 8.50) ÷ 10.00 × 100 = 15% weight loss

Weight Loss as a Consistency Metric¶

Tracking roast weight loss for every batch of the same green coffee at the same target roast level provides a practical consistency indicator. If weight loss increases significantly between batches at the same drop temperature, it may indicate:

Extended total roast time (more volatile and CO₂ loss)
A higher effective drop temperature than indicated (probe calibration drift)
Significant change in green coffee moisture content between lots

Production roasters typically establish acceptable weight loss ranges for each coffee and roast target, and flag batches outside the range for review and cupping.

Key Facts¶

Roast weight loss: (green weight − roasted weight) ÷ green weight × 100%
Typical range: 12–22% depending on roast level
Three components: water vapour (~50–70%), CO₂ (~20–35%), volatile compounds (~5–15%)
Increases with roast level and total roast time
Lighter roasts = less weight loss = more roasted kg per green kg (higher yield)
Batch-to-batch weight loss consistency is a production quality control metric
High-moisture green coffee loses proportionally more weight than low-moisture green coffee

References¶

Changelog¶

Date	Change
2026-04-27	Note created

This article is part of All-About-Coffee.com - The comprehensive coffee knowledgebase.