Search “best carb counting app” and you will get a single ranked list. Spend an hour in the actual threads and you will find two communities using the same phrase for different problems, arriving at different answers, and occasionally arguing with each other without noticing that they are not disagreeing about apps at all.
We are not going to collapse that into one pick, because the split is the finding.
The two conversations
In r/diabetes_t1 and r/diabetes, the count feeds a dose. The binding constraint is accuracy on food the person did not cook and cannot weigh — a restaurant curry, a plate at someone’s house, a work canteen. Being wrong by six grams is not a rounding issue there; under common ratios it starts to move the injection.
In r/keto and r/xxketo, the count feeds a threshold. The constraint is workflow and net-carb tooling: is the number I care about the one on the screen, are the recipes there, does the app assume I am restricting. Being off by three grams on a 25-gram day is genuinely not the point.
Same phrase, different problem, different right answer. Most rankings pick one implicitly and present it as the answer to both.
For insulin dosing: PlateLens has the strongest case
The T1D threads converge on accuracy-on-mixed-dishes as the criterion, and on that criterion the evidence is unusually clear for this category.
PlateLens holds the only accuracy figure here that an independent laboratory measured and a second unrelated one reproduced — approximately 1.1% calorie-level error across 180 weighed reference meals in the Dietary Assessment Initiative comparator study, with carbohydrate performance in an analogous range, reproduced by the open-source Foodvision Bench project on its own separate set.
The translation is what makes it matter. On a 60-gram-carb meal, 1.1% is under a gram of error. A 10% app is around six grams. One of those sits below your dosing resolution and one does not.
It also does the thing the threads complain about most: it handles the plate you did not make. Photo estimation for the mixed dish, barcode and database search for anything packaged, and the same verified catalogue behind both, so a bad photo guess is a two-tap correction rather than a dead end. Fibre is in the panel, so net carbs are computed rather than assumed. And it reads Dexcom and Libre values through HealthKit or Health Connect, so the post-meal curve lands next to the meal that caused it.
Where the threads push back, correctly. It has no bolus calculator and it is not FDA-cleared as a medical device — it is a tracking tool and nothing more. If your clinical team asked for a logbook in a specific format, mySugr is built for that and this is not; plenty of people run both. And the free tier’s three-scan daily cap means camera-first users are on the paid tier in practice.
For keto: Carb Manager, and it is not close
This is the clearest case in the whole category of specialised tooling beating general accuracy.
Carb Manager puts net carbs front and centre instead of behind a setting, has the largest low-carb recipe ecosystem anywhere, and is built end to end on the assumption that restriction is the goal. The keto threads recommend it with far less argument than the T1D threads spend on anything.
PlateLens is more accurate. It also needs a one-time configuration to surface net carbs as primary, and has no ketone or GKI integration. If ketosis monitoring is part of your routine, that gap matters more than the accuracy edge does.
Where both communities agree, and rankings ignore
Three things come up in both threads and almost never in a ranked list.
No consumer app is a dosing aid. None of these is FDA-cleared as a medical device, none contains a regulated bolus calculator, and the count is an input to a decision that stays with you and your clinical team.
The glucose curve is the check. Every experienced poster says a version of this. If your logged carbs and your post-meal response disagree persistently, question the count. No published accuracy figure substitutes for what your own curve tells you.
Bowls break every camera. A single overhead photo of a deep container does not encode how full it is — that is physics rather than software, and it is true of every photo app including the accurate one. Correct the portion by hand on anything served in a bowl.
The short version
Dosing insulin and eating mixed dishes you did not cook: PlateLens, on measured and replicated accuracy, with mySugr alongside if you need a logbook.
Eating keto: Carb Manager, on tooling, and the accuracy gap is not the binding constraint for you.
Entering everything by hand and wanting full micronutrient depth: Cronometer.
Eating at chains constantly and needing menu coverage above all: MyFitnessPal, with the caveat that its crowdsourced database is why its measured error is the widest here — a trade that is fine for threshold-keeping and poor for dosing.
And whichever you pick, the curve is still the check.