What Is Rate of Rise in Coffee Roasting?
Rate of Rise (RoR) measures how quickly the temperature of the coffee beans is increasing during a roast, typically expressed in degrees per minute (°F/min or °C/min). Rather than looking only at the bean’s current temperature, RoR tracks the speed of change in that temperature — essentially, how fast heat is being added to the beans at any given moment. Most dedicated roasting software and many roast-logging apps calculate and display RoR automatically from a temperature probe, though it can also be tracked manually.
Because sourcing on this specific topic is thinner than on more mainstream roasting questions, treat the numbers and curve shapes below as general, widely cited patterns rather than exact figures you should expect to match precisely on any particular roaster.
Why Rate of Rise Matters for Flavor
RoR is used as a real-time signal of how roast development is progressing, which matters because the speed of heating — not just the final temperature — affects how a roast tastes:
- A steeper, faster RoR tends to be associated with brighter, more pronounced acidity in the finished coffee.
- A lower, more gradually declining RoR tends to favor more sweetness and body, as the roast develops more gradually.
- Tracking RoR also helps roasters reproduce a roast they liked, since matching a previous RoR curve (not just a previous end temperature) is part of how consistent batches are achieved on the same equipment.
These are general tendencies reported by roasters and roasting-education sources, not a strict formula — the same RoR pattern can produce different results on different machines, beans, and batch sizes.
The Turning Point and a Typical RoR Curve
When room-temperature green beans are loaded into a hot roaster, the beans initially cool the air and metal around them, so bean temperature actually drops for a short period before it starts climbing. The moment temperature bottoms out and begins rising again is called the turning point, and RoR is generally only meaningful (and tracked) starting from that point onward.
From the turning point, a typical RoR curve tends to follow this general shape:
- RoR is usually highest early in the roast, as the beans are heated aggressively to drive off moisture during the drying stage.
- RoR then tends to decline gradually through the browning (Maillard) stage and into and past first crack, as the roaster’s heat input is typically reduced to manage development.
This gradual decline, rather than a flat or erratic line, is generally considered the healthier pattern for producing a balanced-tasting roast.
How to Calculate Rate of Rise
At its simplest, RoR is calculated as the change in bean temperature over a fixed time interval:
RoR = (Temperature at Time B − Temperature at Time A) ÷ (Time B − Time A)
For example, if bean temperature rises from 300°F to 310°F over one minute, the RoR for that interval is 10°F per minute. Most roasting software automates this by sampling temperature at short, regular intervals (often every few seconds to every 30 seconds) and calculating RoR continuously, usually smoothing the result slightly to avoid jumpy readings from probe noise. If you’re tracking manually without roast software, logging bean temperature at consistent intervals (for example, every 30 or 60 seconds) and calculating the difference by hand gives you a workable, if less precise, approximation.
Common RoR Problems: Flicks, Crashes, and Stalls
A few recurring issues come up when watching an RoR curve:
- Flicks — a sudden upward spike in RoR, often from a late increase in heat. This can scorch the outside of the beans or create uneven, harsh flavors if it happens late in the roast.
- Crashes — a sudden, sharp drop in RoR, often from cutting heat too aggressively. This can produce a flat, “baked” taste if the roast’s internal development doesn’t keep pace with the drop.
- Stalls — RoR flattening out near zero for an extended stretch, meaning the beans have essentially stopped heating up. Similar to a crash, this is associated with dull, baked, or underdeveloped flavor, since the chemical reactions that build roast flavor need continued heat input to progress properly.
Generally, a smoother and more gradually declining RoR curve, without sharp flicks, crashes, or stalls, is considered more likely to produce a clean, well-developed cup — though exact target curves vary by roaster, bean, and desired roast level, which is part of why experienced roasters keep detailed logs across batches.
Rate of Rise and Development Time Ratio
Development time ratio (sometimes abbreviated DTR) is a related concept: the percentage of total roast time spent after first crack, relative to the whole roast. It’s often discussed alongside RoR because the two interact — a particular RoR pattern heading into first crack affects how much development time is needed afterward to reach a given roast level.
This concept is closely associated with coffee roasting educator Scott Rao, who has written about roast development and the risks of “baked” coffee from poor heat management. Because we don’t have a strong, verifiable citation for a specific numeric development-time-ratio figure attributed to him, we won’t state one here — if you’re looking for a specific target percentage, it’s worth checking his own published writing directly rather than relying on a secondhand number. The broader, well-supported takeaway is simply that both the RoR curve before first crack and the proportion of time spent developing after it play a role in how a roast ultimately tastes.
FAQ
What is the 15-15-15 coffee rule? This isn’t a term with a single clear, widely documented definition tied specifically to rate of rise. It’s sometimes mentioned as a loose home-roasting guideline for overall roast and cooldown timing rather than a rate-of-rise standard — treat any specific numbers attached to it cautiously.
How to calculate rate of rise coffee? Divide the change in bean temperature by the time elapsed: (temperature at the later time minus temperature at the earlier time) divided by the time difference, typically expressed in degrees per minute. Roasting software automates this from continuous temperature readings.
What is the average profit margin for coffee roasting? This varies widely depending on scale, business model (wholesale versus direct retail), and local costs, and isn’t something we have strong, reliable figures to state confidently. As a general business question it’s outside the core scope of this roasting-mechanics guide.
What is Scott Rao’s development time ratio for roasting? Scott Rao is closely associated with development time ratio as a concept in coffee roast development, but we don’t have a confident, verifiable specific number to cite here. If you need an exact figure, his own published material is the more reliable source to check directly.