Carb counting from a food photo: how it works and how accurate it is
If you count carbs, you know how much time goes into searching a database, guessing grams and adding them up at every meal. Karbi is a photo carb counting app that cuts this to a single step: you take a photo of the food and get an estimate. Below I describe how it works, how accurate it is, and what to watch for.
How does the Karbi app estimate carbs from a photo?
Karbi recognises the food and its ingredients in the photo, estimates the portion size, and works out the carbohydrate, fat, protein and calorie content from that. It also shows whether the carbohydrate is absorbed over a short, medium or long time.
Every photo is checked by two independent assessments. If they disagree, or the food is hard to judge, Karbi tells you it is worth a look. You can edit the estimate before you save it, and the diary keeps your correction.
How accurate is a photo carb estimate?
I weighed 25 dishes to the gram and worked out their real carbohydrate, fat, protein and calorie content. Most of them were Hungarian dishes (pork stew, stuffed cabbage, lángos, aranygaluska), a few were fast food or packaged products. I compared Karbi's estimate with that: the carb estimate was off by about 7 grams on average; two thirds of the estimates were within 10 grams, and almost all of them within 15 grams.
It is an estimate, not a measurement. If you need an exact value, weigh the food or read the nutrition table on the package.
What does the photo not show?
Karbi sees what is in the picture. It cannot see, for example:
- the oil or fat the food was cooked in;
- flour, sugar or thickening stirred into a sauce;
- what is under the pasta or the topping;
- the exact size of the portion, if nothing in the picture gives a sense of scale.
It works best when the whole portion is in the picture, the light is good, you shoot from above or slightly from the side, and the plate, a piece of cutlery or your hand is visible. Whatever the photo does not show, you can correct by hand before saving, and you can save your own recipes with their exact values.
Who do I recommend Karbi to?
For anyone who counts carbs or calories regularly and does not want to work it out from a table at every meal:
- people with type 1 or type 2 diabetes who count carbs every day;
- people who watch their carbs because of insulin resistance or a low carb diet;
- people who want to lose weight or who train, and track calories and protein.
I have type 1 diabetes, I count my own carbs this way, and I build Karbi for the Hungarian diabetes community.
Karbi is not a medical device: it does not calculate insulin doses and does not give medical advice. It gives nutritional information about the food.
How is it different from a database calorie counter?
In a database app you search for the food, pick the closest entry and estimate the grams. For home-cooked and restaurant food that is the hardest part, and that is the step a photo estimate takes over. In Karbi you can also look up packaged products by barcode; there the label on the package is what counts.
Trying it
Karbi can be used for free, and you can try the photo estimate for free too: 3 estimates without an account, 5 more with one.
Karbi's packages on the home page · The limits of the estimate in detail