Development time ratio (DTR)

The percentage of a coffee roast spent between first crack and the moment the beans are dropped from the roaster. If the total roast time is 10 minutes and first crack is at 8:30, the DTR is 15%.

Why it matters — DTR is a key variable roasters use to shape coffee flavour. Lower DTR (under 15%) tends to produce brighter, more acidic coffee; higher DTR (over 22%) tends to develop more sweetness, body, and roast character — sometimes at the cost of acidity and clarity.

Good to know

• Typical specialty DTR ranges from 18–25%.
• DTR alone doesn't define the roast — total time, temperature curve, and bean origin all interact. It's one variable, not the only one.