Barcode Calorie Lookup: Scan Packaged Food

The stripes on a pack encode a number called a GTIN. Most food in shops uses 13 digits (EAN-13). The scanner reads the digits, and the app sends them to a food database. If the number is there, you get the product name, the nutrition values per 100 g and sometimes the pack size.

The last digit is a check digit. It is calculated from the first twelve. Multiply the digits at odd positions by 1 and at even positions by 3, add them up, and the check digit is whatever brings the total to a multiple of 10. For 4006381333931 the sum of the first twelve is 89, so the check digit is 1. If a typed code fails this test, a digit is wrong, and no database will find it.

The scanner does not measure anything about the food. It only identifies the pack. The calories come from whoever entered the label into the database, which is why the source matters.

Mealyno looks codes up in Open Food Facts, an open, crowd-sourced food product database, using both the world database and the Ukraine one, plus a cache of products already found. Volunteers and brands add products by photographing the pack and typing the label, so coverage follows how many people have contributed in a given country.

Because it is crowd-sourced, an entry can contain a typing error or an old recipe. If a number looks odd next to the pack in your hand, trust the pack.

Local brands and small producers are added more slowly than international ones. A pack can also be new, renamed or sold only in one region. Codes from the same producer can differ by weight or flavour, so a close match for the same yogurt in a different size may not exist.

A miss does not mean you did something wrong. It means the database has no record for that exact code yet.

You photograph the nutrition table on the pack. The AI reads the values as they are printed, per 100 g or per serving, checks that the kcal figure agrees with the protein, fat and carbohydrates, and shows the result in an editable form. If it has to estimate, the result is marked approximate.

Reading a label this way is an AI scan, so it uses one photo scan and not the free barcode lookup. A free account has 3 photo scans in total, and the no-signup photo tool allows one a day. After you correct the numbers, you can save the meal as one of your dishes and log it again in one tap.

A label in Ukrainian lists the same values as any other, in a fixed order. Learn these terms and you can read most packs.

Say a chocolate bar label shows per 100 g: 520 kcal, 6 g protein, 30 g fat, 55 g carbohydrates. You eat 45 g. The factor is 45 / 100 = 0.45.

Calories: 520 × 0.45 = 234 kcal. Protein: 6 × 0.45 = 2.7 g. Fat: 30 × 0.45 = 13.5 g. Carbohydrates: 55 × 0.45 = 24.75 g, about 24.8 g.

Quick check: 2.7 × 4 + 13.5 × 9 + 24.75 × 4 = 10.8 + 121.5 + 99 = 231.3 kcal, close to 234. A small gap is normal because labels round values and fibre is counted differently.

Most wrong numbers start with a misread label.

Among the apps we checked, Welmi lists photo, voice and barcode logging, and Cal AI lists barcode scanning on its site. Barcode scanning is not mentioned on the TrackAI site or its store page, and a May 2026 App Store review of TrackAI says it does not search by barcode and that many products are missing. We did not verify barcode support for the other apps.

In Mealyno, barcode lookups are free and unlimited with an account. It runs in the browser, so scanning uses your phone camera through the web page, and there is no App Store app yet.