What does "accurate" mean for a calorie counter?
That the figure on the screen is close to what you ate. Two things make it so: the calories per 100 g of the food, which come from a composition table or a nutrition label, and the grams on your plate, which come from you. An app can be right on the first and useless on the second.
The evidence on the first part is reassuring. In a 2020 study in *JMIR*, Evenepoel and colleagues had 50 people record four days of meals in MyFitnessPal, with instructions on how to pick an entry, and compared the result to Nubel, the Belgian food composition database: energy came out 1.3 percent high. Picked with care, a tracker's database is a reference table with extra steps.
The evidence on the second part is where the trouble is. An app's figure and a model's figure fail differently, and what a model's confidence is worth is its own page. In an app, the same crowd-sourced database holds ten entries for one food, and the community's complaint is not that the right one is wrong but that it has to be found: "Same food, ten results, ten calorie counts" (reviews of MyFitnessPal, read 4 September 2026). Then comes the portion, which no database knows.
Where does a calorie count go wrong?
In four places, each of which can move a figure a long way, and none of which is the app's arithmetic. Steamed against boiled, boiled against baked, changes the figure by a few kilocalories per hundred grams, which is why those rarely deserve a question.
| The error | How large it can be | What fixes it |
|---|---|---|
| The wrong entry among ten | Any size: a different product, a different portion definition | Read the label, or name the plain food and its weight |
| The unweighed portion | 20 to 54 percent average error when a photo guesses it, in a community test of five vision models against a scale, read 4 September 2026 | A weight, or one portion cue you can check: spoonfuls, a fraction of the plate, a known container |
| The cooking fat | 10 g of oil is about 88 kcal, invisible on the plate (USDA FoodData Central, checked 15 September 2026) | Say what it was cooked or dressed in; record the fat as its own item |
| Raw taken for cooked | Dry pasta is about 371 kcal per 100 g, cooked about 158; rice 365 against 130 (USDA, same check) | Say which weight you took; for meat, cooked is assumed and said |
Bottom line: the app is rarely the error; the entry, the portion and the fat are, and a counter is accurate to the degree it makes you say them.
What the community measured matches this. The r/loseit member who tested five vision models with a kitchen scale found the models "always know what the food is" and "just can't tell how much is on the plate"; a 50 g sweet potato was guessed at 150 g. The error was never the calorie table. It was the portion, and the oil nobody could see.
Why does the source of a number matter more than the app?
Because two figures of 480 kcal are not the same fact. One was read from a label the producer measured; the other was guessed from a photo. A counter that shows both the same way has hidden the only thing you needed to know: how far to trust the number. The source is what makes a total honest.
- A label is the producer's declared values for that product, not a measure of the portion you ate. It is the figure you can check against the pack, and its calorie figure is kept as printed, never recomputed from the macros.
- A reference value is a composition table's figure for a plain food, scaled to the weight you said: cooked rice, raw chicken, an apple.
- Your own figure is what you read or weighed yourself, recorded as yours.
- An estimate is everything else: a restaurant plate, a homemade dish, a portion nobody weighed. Useful, and honest only when it is called an estimate.
The people who distrust calorie counting say this in their own words. What they hate is not the estimate; it is the estimate dressed as a measurement, the number given "with absolute certainty despite all the ways it can introduce errors" (r/loseit, read 4 September 2026).
How accurate is a nutrition label?
Accurate enough to be the best source you have, and worth reading with care. A label's calorie figure is the producer's declaration, computed from the grams of protein, carbohydrate, fat, fibre and alcohol with fixed factors, 4, 4, 9, 2 and 7 kcal per gram in Regulation (EU) 1169/2011, read 14 September 2026.
Two things go wrong at the reading, not at the label. The unit: European labels print kilojoules and kilocalories side by side, 1 kcal being 4.184 kJ, and a kJ figure read under a kcal heading is about four times too high. The serving: a figure per serving is only usable with the serving's weight, which the label gives somewhere on the panel, and a serving is often smaller than what was eaten.
This is where the assistant earns its place: through IZeat it is asked to read the label's values back to you before anything is recorded, unit and serving included, and it can add what it sees: a kJ figure where kcal was meant, an energy figure that does not fit the grams. That is where 1.2 g taken for 12 g can be caught, by you or by it; a flagged mismatch is a question to settle, not a verdict on the label.
How can you check and correct the numbers in your diary?
IZeat is the calorie tracker inside ChatGPT, Claude or any other assistant. Tell the assistant you already use what you ate instead of searching for foods and entering them one by one. It promises no better figure than a scale and a label give; what it gives you is the means to see which figure is which, and to change one in a sentence, so the diary you count on stays worth counting on.
Thursday lunch: "150 g of cooked rice, and here is the label of the sauce, I had 40 g." The assistant reads the label back to you, per 100 g, 1.2 g of fat and not 12, and would say so if the kJ figure did not fit the grams, before anything is recorded; IZeat stores the rice as a reference value and the sauce with the label as its source, both scaled to your grams, and returns the receipt with the day so far. Later you find the figure you had noted from the scale: "the rice was 200 g, not 150." The assistant updates the row through IZeat; the day is summed again from its rows; the previous state stays in the meal's history, so you can always ask what was recorded and when.
| What you say | The source recorded | How far to trust it |
|---|---|---|
| "Here's the label, I had 40 g" | Label: the producer's declared figures, scaled to 40 g, read back to you | As far as the producer's declaration for the product |
| "150 g of cooked rice" | Reference: a composition table's value for cooked rice, scaled | As far as the table, for a plain food |
| "Log it at 210 kcal, I calculated it" | Yours: the figure you gave | As far as you |
| "Chicken curry, about a plate, cooked in ghee" | Estimate: each item marked as one | As an estimate, and shown as one |
| A photo of the plate, no words | Nothing yet: the assistant is asked for a portion cue and the fat first | Not at all, until you answer |
Bottom line: accuracy you can check beats accuracy you have to believe; the source on every item is the check, not a certificate.
- You never pick among ten entries again. There is no crowd-sourced database: a label is read, a plain food is valued from a standard table, the rest is an estimate that says so.
- You are asked one bundled question, when a missing fact would change the figure. The portion, the cooking fat, raw or cooked weight, which variant; what your words already settle is not asked again.
- You see what was recorded the moment it is recorded. The receipt comes back item by item with its source, the meal total and what is left for the day; a wrong row is seen at once and corrected in a sentence, and the day follows.
Frequently asked questions
Short answers to the questions people type, each one sourced above.
Which calorie counter app is the most accurate?
None can be more accurate than its input. In a 2020 study where people recorded four days in MyFitnessPal with instructions on picking entries, energy came out 1.3 percent high against Nubel, the Belgian reference, so the databases are usable; the error comes from picking the wrong entry, from the unweighed portion and from the cooking fat. The useful question is which app tells you how each number was obtained, and IZeat stores that source on every item.
Is MyFitnessPal accurate?
Its database is, on energy, when the right entry is picked: a 2020 study in *JMIR* found energy 1.3 percent high against Nubel, the Belgian reference, with instructed users. Nutrients are another matter: a 2024 study in *JMIR mHealth and uHealth* by Ho and colleagues found four apps, MyFitnessPal among them, under-estimating saturated fat by 13.8 to 40.3 percent. The complaint in the reviews is the picking: ten entries for one food, and no way to know which is right.
How accurate is ChatGPT at counting calories?
As accurate as the description it is given. With a dish, a weight and a brand, it values a meal the way a table does; with a photo, a community test of five vision models against a kitchen scale found 20 to 54 percent average error on portion size, and no model can see cooking fat. Used through IZeat, it is asked for the portion and the fat before anything is recorded, and the result is marked as an estimate.
Are nutrition labels accurate?
They are the producer's declared values, computed from the macronutrient grams with the fixed factors of the European regulation, and they are a source you can check against the pack, not a measurement, and they can carry an inconsistency of their own. What goes wrong more often is the reading: kilojoules taken for kilocalories, or a per-serving figure applied to a bigger portion. Through IZeat, the assistant reads the values back before anything is recorded and can say when an energy figure does not fit the grams; no check catches every error.
Why do two apps give different calories for the same food?
Because they hold different entries: one has the producer's label figure, another a user-typed copy of a different size of the same product, a third a generic value from a composition table. A cooked and a raw weight of the same food also differ by two to three times for pasta and rice. The apps are not disagreeing about the food; they are describing different entries, and rarely tell you which.
What is the most accurate way to count calories?
Weigh plain foods and value them from a composition table; read the label for packaged foods and scale it to the grams you ate; say what a dish was cooked in and record the fat as its own item; and record anything you did not weigh as an estimate, so the day says how sure it is. IZeat does the recording and the sources; the scale and the label are still yours.
Is an estimate useless if it is not accurate?
No. An estimate reasoned from the dish, the portion and the fat is a real figure with a known uncertainty, and a day with one estimated dinner is a normal day. What is useless is an estimate dressed as a measurement, which is what the calorie-counting communities distrust. IZeat records an estimate as an estimate and shows it beside the label and table figures as what it is.
Does IZeat use a food database?
Not a crowd-sourced one, and it looks nothing up itself. A label you photograph or paste is read by the assistant and recorded as a label; a plain food you weighed is valued by the assistant from a standard composition table and recorded as a reference value; a figure you give is recorded as yours; the rest is an estimate, marked as one. There is no search box and no list of ten entries.
Do I need to be accurate to lose weight?
The research answered a neighbouring question: a 2019 trial that timed food recording found that how often people recorded, not how long they spent, went with the trial's outcome, and fewer than half of the participants in two six-month trials were still recording after ten weeks. Accuracy was not what they measured. IZeat records what you ate, estimates marked as such, and compares the day to the target you chose; it does not prescribe a diet or promise a result.
How do I make my calorie tracking more accurate?
Give the four things that move a figure the most: the right entry, by reading the label or naming the plain food; the weight, or one portion cue you can check; the cooking fat, said out loud; and which weight you took, raw or cooked, for pasta, rice and meat. Under IZeat's protocol the assistant asks one bundled question about the missing details that would materially change the estimate, then states the assumptions it still had to make, and a correction later is one sentence.