Estimate roasted yield, development time ratio (DTR), and bean cost per cup from a single roast batch.
Why a roast calculator matters
Roasting coffee is both craft and measurement. You can rely on color, smell, and sound, but if you do not track numbers, consistency becomes guesswork. A roast calculator helps you connect sensory decisions with repeatable metrics: yield, development ratio, and production cost.
This is especially useful for home roasters and small-batch professionals who want to answer practical questions quickly:
- How much roasted coffee will I end up with?
- Is my development time too short or too long?
- What does each cup cost based on my green coffee price?
What this roast calculator computes
1) Roasted output and moisture loss
During roasting, beans lose moisture and volatile compounds. That weight reduction is normal and expected. With your green input weight and target loss %, the calculator estimates final roasted weight and total grams lost.
2) Development Time Ratio (DTR)
DTR compares post-first-crack development time to total roast time. It is a simple way to see whether a roast may lean underdeveloped, balanced, or heavily developed.
3) Cost per roasted kilogram and cost per cup
As beans lose weight, your cost per roasted kilogram rises. The calculator accounts for that change and gives a realistic cost-per-cup estimate based on brew dose.
Input guide and practical ranges
- Roast weight loss: typically 12% to 20% depending on roast style and bean density.
- Total roast time: commonly 8 to 14 minutes for many drum-style profiles.
- First crack time: often around 70% to 85% of total roast time.
- Dose per cup: 15g to 22g is common for filter and espresso-style recipes.
If your first crack time is equal to or greater than total roast time, the profile inputs are invalid and should be corrected.
How to use this tool step by step
- Weigh your green coffee accurately before roasting.
- Enter your expected or measured loss percentage.
- Input total roast time and first crack time in minutes.
- Add your green coffee cost per kilogram and your brew dose.
- Click Calculate Roast Metrics and review yield, DTR, and cost outputs.
Interpreting your results
Roast level from weight loss
Weight loss can act as a useful proxy for roast degree:
- Below 12%: very light roast zone
- 12–14%: light roast zone
- 14–16%: medium roast zone
- 16–18%: medium-dark roast zone
- Above 18%: dark roast zone
DTR quick interpretation
- <18%: risk of underdevelopment
- 18–22%: bright and lively profile range
- 22–26%: balanced sweetness and body
- 26–30%: deeper development and heavier body
- >30%: risk of baked or flat character
These are directional ranges, not strict rules. Bean origin, processing method, and roast machine behavior can shift ideal targets.
Example scenario
Suppose you roast 1,000g of green coffee at 15% loss, with first crack at 8:00 and total roast time at 10:00. You will finish at roughly 850g roasted coffee. If green coffee cost is $12/kg, your effective roasted cost rises because of mass loss, and your per-cup bean cost can be estimated from the dose you choose.
This gives you better pricing control for cafés, pop-ups, subscription packs, or personal budgeting.
Common mistakes to avoid
- Using estimated weights instead of measured weights.
- Ignoring scale calibration drift.
- Comparing DTR across very different roast systems without context.
- Forgetting that airflow and charge temperature can change outcomes even when times look similar.
Final takeaway
A roast calculator does not replace your palate—it strengthens it. Track yield, development, and cost together, then cup the results and adjust one variable at a time. Over a few batches, you will move from “pretty good” to intentionally repeatable roasting.