Barcode
Barcode — A printed product code, usually a 12-digit UPC or 13-digit EAN, that a calorie tracker's scanner reads to find a packaged food's record.
What the stripes actually encode
The barcode on a packet of crackers holds a number and nothing else. In North America it is usually a 12-digit UPC-A; in most other countries a 13-digit EAN-13. Both are forms of the Global Trade Item Number managed by GS1, and both identify a product, not its nutrition. There are no calories in the stripes.
When you scan, the app does two jobs. The camera decodes the digits, which is the easy part on any modern phone. Then the app looks those digits up in its own food records and shows you what it has stored. Everything you care about, from calories to fibre, comes from that second step.
How a scanner checks it read the code correctly
The last digit of a UPC is a check digit, calculated from the other eleven, so a scanner can tell when it misread a stripe. Take the code 03600029145, which still needs its twelfth digit:
- Add the digits in the odd positions: 0 + 6 + 0 + 2 + 1 + 5 = 14, then multiply by 3 to get 42.
- Add the digits in the even positions: 3 + 0 + 0 + 9 + 4 = 16.
- Add the two: 42 + 16 = 58.
- The check digit is whatever brings that up to the next multiple of ten: 60 − 58 = 2.
So the full code is 036000291452. If the camera reads any single digit wrongly, the sum no longer works out and the scan is rejected instead of returning the wrong product.
Where a scan can still go wrong
A perfect read can still produce a wrong number, for reasons that have nothing to do with the camera:
- No record. Store brands, imports and small producers are often missing.
- A stale record. Manufacturers change recipes; the database may still hold the old label.
- A mismatched serving. The stored portion might be one biscuit while you ate four.
- A conflicting record. In databases that members can edit, one code can end up with more than one set of values.
The practical habit is to glance at the product name and serving size on screen before you save. If either is off, change the amount, or enter the food by name instead.
Choosing an app with a scanner worth using
Two questions matter. First, will the scanner keep working without a subscription? When we read the store listings on October 1, 2026, MyFitnessPal and Lose It! reserved scanning for Premium, MacroFactor had a week-long trial instead of a free plan, and Cronometer let free users scan alongside ads. Second, how good are the records behind it? That is a food database question.
PlateLens illustrates both points. Its scanner has no daily cap and its free tier has no expiry date, and each code is matched to checked records covering 820K+ branded products. Loose fruit, home cooking and other code-less food go into the same diary by photo, typed search or voice.
We compare each app’s plan in our guide to free barcode scanning in calorie trackers.