Coffee Development Time Ratio Calculator
Created by: Liam Turner
Last updated:
Calculate DTR from first crack to drop and compare against style-specific ranges.
Development Time Ratio Calculator
CoffeeCheck post-first-crack development against roast style targets
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What is a Development Time Ratio Calculator?
Balancing post-crack development
A development time ratio calculator shows how much of your roast occurs after first crack. It helps tune sweetness, acidity, and body balance.
This metric is widely used for process consistency and profile communication in production roasting.
Using DTR as a shared reference can reduce subjective disagreements during profile review. It gives teams a common language for end-of-roast control.
DTR Formula
From event times to ratio targets
Development Time = Drop Time − First Crack Time DTR (%) = Development Time ÷ Drop Time × 100
Evaluate DTR against your target style range, then validate with cupping results.
The strongest decisions come from combining DTR with color, end temperature, and sensory data rather than using a single metric alone.
Example
20% DTR interpretation
If first crack starts at 8:40 and drop is at 10:50, development is 2:10 and DTR is about 20%. That often aligns with medium filter roast targets.
If cup results feel underdeveloped, you may test a modest increase while monitoring body and acidity impact. Small, logged adjustments usually work best.
Applications
Consistency and transfer workflows
Use DTR for roast profile transfer, training alignment, and lot-to-lot consistency monitoring.
It is especially helpful when multiple operators share the same profile family and need objective checkpoints for handoffs.
Tips
Keep event timing definitions fixed
Document how your team marks first crack and drop so DTR values stay comparable over time. Even small timing-definition shifts can distort trend analysis.
Pair DTR with end temperature and color data for stronger quality decisions.
Keep event definitions consistent across operators to avoid timing drift.
Frequently Asked Questions
What is development time ratio (DTR)?
DTR is the percentage of roast time spent after first crack starts. It is commonly used to gauge roast finishing balance and sweetness development.
Is higher DTR always better?
No. Too low can taste underdeveloped and too high can mute acidity or add baked notes. The best range depends on bean type and intended brew method.
How should I use DTR in practice?
Use DTR as one control variable with end temperature, color, and cup score. Do not optimize DTR in isolation.
Can DTR help transfer profiles?
Yes. Keeping a similar DTR while adjusting heat and airflow can help maintain roast style across different batch sizes.
Sources and References
- Rao, Scott. The Coffee Roaster’s Companion. Development control and roast balancing strategies.
- Specialty Coffee Association resources on roast style and process consistency.