Development Time Ratio on a Kaffelogic: 75 Roasts of Data
We checked the usual DTR rules against 75 logged Kaffelogic roasts. 86% of the variation in DTR came from which profile was loaded, and our best cups landed anywhere from 10% to 24%.
BrewedLate Coffee
Roasting guides give development time ratio (DTR) as a set of bands: under about 10% tastes grassy, over about 25% tastes baked, and filter roasts want something in between. We wanted to know whether that holds on a Kaffelogic, so we checked it against 75 roasts logged on a Nano 7e across six beans and eleven profiles.
The short answer: on a Kaffelogic, DTR mostly tells you which profile was loaded. 86% of the variation in DTR across our roasts came from the profile. Our best cups landed anywhere between 10% and 24%.
If DTR is new to you, first crack in coffee roasting explains what it measures. This post is about what the number does and does not tell you once you start comparing roasts.
Every scored roast, by profile
Cup score vs development time ratio
Each dot is one scored roast on a Kaffelogic Nano 7e: 68 roasts across 6 beans, one roaster.
- F-WSH 1500-2200(20)
- F-NAT 0-1200(9)
- NCT Filter D(8)
- NCT Filter E(5)
- NordicLight(6)
- Other profiles(20)
The dots form vertical bands. Each profile sits in its own narrow range of DTR, and within each band the scores run from poor to excellent.
| Profile | Roasts | DTR range | Median DTR | Median cup score (of 5) |
|---|---|---|---|---|
| NCT Filter D | 8 | 6.5–14.6% | 8.7% | 3.5 |
| NCT Filter E | 7 | 10.8–12.5% | 11.7% | 4 |
| NCT Filter B | 4 | 10.3–12.7% | 11.8% | 4 |
| 9minFilter | 6 | 9.8–15.7% | 12.8% | 3.5 |
| F-WSH 1500-2200 | 22 | 12.8–21.9% | 16.3% | 3 |
| F-WSH 1000-1700 | 5 | 15.3–18.1% | 17.4% | 2.5 |
| F-NAT 0-1200 | 11 | 17.1–25.3% | 20.8% | 4 |
| NordicLight | 7 | 22.1–24.4% | 23.5% | 3.5 |
| Raost variants | 3 | 24.3–33.5% | 26.7% | 2 |
NCT Filter D at 8.7% and NordicLight at 23.5% have the same median score. NCT Filter E never left a band less than two points wide, yet its roasts scored from 2 to 4.5.
Why the profile sets the number
A Kaffelogic does not hear first crack. Every profile file carries an expected first-crack temperature, and the roast log marks first crack at the moment the bean temperature crosses it. Development time is counted from that crossing.
Profile designers put that marker in different places. F-WSH 1500-2200 sets it at 206 °C. NCT Filter D sets it at 215.5 °C, and NCT Filter E at 217.5 °C. A roast that ends at 220 °C has spent much longer above 206 °C than above 217.5 °C, so the same physical roast would report a very different DTR depending on which marker it was measured against. We go through the marker and curve differences in NCT vs F-Series compared by the numbers.
One bean, six profiles
The cleanest test is a single coffee roasted on several profiles. This is a washed Ethiopia Sidamo:
| Profile | Roasts | Median DTR | Median cup score |
|---|---|---|---|
| NCT Filter D | 2 | 7.3% | 3.25 |
| NCT Filter E | 3 | 12.3% | 4.5 |
| 9minFilter | 1 | 15.7% | 2 |
| F-WSH 1500-2200 | 3 | 16.3% | 2.25 |
| NordicLight | 3 | 23.3% | 3.5 |
| Raost Sidamo | 1 | 24.3% | 2 |
Read down the DTR column and the scores follow no pattern: the best and the worst results sit next to each other. If you took the F-WSH result at 16.3% and concluded the roast needed more development, NordicLight at 23.3% would seem to confirm it, and NCT Filter E at 12.3% would be the last thing you tried. It was the best cup.
Ethiopia · Sidamo · Washed · 1,400-2,200 MASL · G2 · John Burton
aroma of caramel, lemon flower and spices. Flavours of madeira cake and black tea with lemongrass undertones. Long lemon black tea finish. Crispy acidity, medium coating body. Score: 82.5+
““nice and fruity, smooth, a little darker, could probably be roasted a tick lighter.”
Winning batch R-094 · 2026-07-14
Cup quality across 13 attempts
Each point is a roast scored from tasting notes (1 = miss, 5 = dialed in). The series stops at the teal halo — once dialed in, later repeats aren’t scored the same way.
Where the good cups live
Roast level vs batch size. Color = profile family; larger dots = better cups. Notice how quality clusters once batch size moves to 100–120g.
Roast mechanics that stuck
DTR, roast loss, and rate-of-rise across attempts with klog data. Each series is scaled on its own axis so shapes are comparable.
What the data taught us
- 1NordicLight ~2.8 / 120g (R-037) first hit “nice and fruity” after rest — early 9min/Raost runs were green or dark-flat.
- 2NCT Filter E around 2.2–2.5 / 100g became the cleaner modern lane (R-069, R-094): fruity, no green, watch for a touch dark.
- 3F-WSH 1500-2200 at 2.3 was awful underdeveloped on this lot — same family that works for Gatugi is not automatic here.
- 4Current fine-tune: Filter E at 2.0 (R-101) after “tick lighter” feedback on R-094.
Want to log a journey like this?
Track profiles, klog metrics, and tasting notes until the cup clicks.
Do the textbook bands hold?
Partly.
- Over 25%: yes. Four scored roasts ran above 25%. They scored 1.5, 1.5, 2.5 and 3.5. None was a cup we would repeat.
- Under 10%: no. Six scored roasts ran below 10%, five of them on NCT Filter D. They scored between 2 and 4.5, with a median of 3.5. One of our twelve best roasts had a DTR of 9.8%.
- A target range: no. The eight best-scoring roasts with a logged DTR (4.5 or higher) had DTRs of 9.8, 10.3, 12.0, 12.2, 14.3, 15.4, 19.7 and 24.2%.
Across all 68 roasts with both a score and a DTR, the correlation between the two was weak and negative (r = −0.29). After removing each profile's own median it was weaker still (r = −0.18).
Where DTR is useful: inside one profile
On a single profile the marker stays put, so DTR means something. What it mostly means is the level you chose. Across 21 roasts on F-WSH 1500-2200, level and DTR moved together almost exactly (r = 0.95), from about 15% at level 2.0 to about 20% at level 3.0.
On that profile, lower was better for the washed coffees we ran through it: roasts scoring 4 or more had a median DTR of 14.9% at level 2.0, and roasts scoring 2.5 or less had a median of 17.4% at level 2.45. That is a usable rule for that profile and those beans. It does not carry over to another profile.
How to use this
- Compare DTR only between roasts on the same profile. There it is a quick check that a level change did what you expected.
- When you switch profiles, start again. A 12% on NCT Filter E and a 12% on F-WSH 1500-2200 are different roasts.
- Across profiles, compare what does not depend on the marker: drop temperature, total time, roast loss and, above all, the cup.
- Treat published DTR bands as belonging to the roaster and profile they came from. The over-25% warning held up for us. The under-10% one did not.
These are one roaster's logs and one palate, with a handful of roasts on most profiles, so read the scores as directional. The full attempt history for each bean is in the roast logs.
See your own DTR by profile
Upload your Kaffelogic .klog files and BrewedLate works out first crack, DTR and roast loss for every batch, grouped by bean and profile.
Related Reading
- First crack in coffee roasting — what first crack and DTR are
- NCT vs F-Series compared by the numbers — where each family puts its first-crack marker
- How to roast Ethiopia Sidamo — the full story behind the six-profile table
- Coffee roast log template — the fields worth recording for every batch
Frequently Asked Questions
What is a good development time ratio on a Kaffelogic?
Why is my DTR so low on NCT profiles?
How does a Kaffelogic calculate development time?
Is a DTR under 10% always underdeveloped?
Does a higher roast level increase DTR?
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