What is DTR?
Development time is the time between the start of first crack and the drop. DTR is that time divided by the total roast time, times 100. If a roast lasts 10 minutes and development lasts 2 minutes, the DTR is 20%. DTR helps compare roasts of different lengths on one scale. See first to second crack.
| Total roast time | Development time | DTR |
|---|---|---|
| 10:00 | 1:45 | 17.5% |
| 10:00 | 2:00 | 20% |
| 11:00 | 2:45 | 25% |
Typical DTR ranges
| Style | Typical DTR | Cup tendency |
|---|---|---|
| Light, filter | About 15–20% | Bright, floral, clear |
| Medium, versatile | About 18–23% | Balanced sweetness and acidity |
| Espresso and milk | About 20–25% | Sweeter, rounder, lower acidity |
Beans, roasters and taste vary, so use your own cupping results to set targets. See roasting levels and espresso roast vs filter roast.
What DTR changes in the cup
- Short DTR: brighter, more acidic, but a risk of sour, grassy, underdeveloped flavours.
- Balanced DTR: sweetness, clarity and body in proportion.
- Long DTR: rounder, heavier, roastier, with lower acidity; too long tastes flat.
See roast defects 101 for sour and baked faults.
How to tune a roast with DTR
- Cup first: is the coffee sour or flat?
- If sour or grassy: lengthen development a little, by 5–10 seconds at a time.
- If flat or roasty: shorten development or reduce late heat.
- Keep other variables steady: batch size, charge temperature and airflow.
- Log every change. See how to roast green coffee.
DTR for different coffees
Dense, high-grown Arabica tolerates more energy and a clear development; low-density or Robusta beans often need a gentler approach. See density and moisture, how to roast Robusta and how to roast Ethiopian coffee.
FAQ: Development time ratio
How do you calculate DTR?
Divide the development time (first crack to drop) by the total roast time and multiply by 100.
What is a good DTR for light roast?
Often around 15–20%, but taste and equipment decide.
What DTR suits espresso?
Many roasters use roughly 20–25%, but test your blend.
Does a higher DTR mean a darker roast?
Not necessarily, but longer development usually adds body and lowers acidity.
Why does my coffee taste sour at a low DTR?
Development may be too short; the coffee is underdeveloped. See roast defects 101.
Can DTR fix a baked roast?
Not alone. Baked coffee usually needs rate of rise and energy changes too.
How accurate do my timings need to be?
Within a few seconds. Mark first crack consistently.
Is DTR the same across roasters?
Numbers differ, so build your own targets from cupping.
