03 — Barcode logging

Barcodes, done in a second.

Packaged food has its numbers printed on the box. CalorieCounter reads the barcode, finds the product, and asks only one question: how much did you have?

By Alen Yaco · Double bachelor's in biological sciences and social ecology, UC Irvine · Published 17 September 2026

How does barcode scanning work in a calorie tracker?

You point the camera at the barcode on the pack. The code is read on your phone in about a second, matched against a nutrition catalog, and the product opens with its serving sizes already filled in. Pick a serving or type grams, then save it to a meal.

1. Point at the code. Open the scanner from the Today screen or from any meal. The camera reads standard retail barcodes on its own; there is nothing to line up.
2. The product appears. Name, brand, nutrition per serving, and the source of the data shown on the row.
3. Pick the amount. One serving, half a bag, 37 g: use the serving list, the stepper, or type a number.
4. Save to a meal. It lands in breakfast, lunch, dinner, or snack, and the ring updates.

Where does the nutrition data behind a barcode come from?

Packaged products come from Open Food Facts, an open database maintained by contributors worldwide, and generic foods come from USDA FoodData Central. Both are credited in the app. When a product carries a printed label, that label is the source of truth for what you logged.

Every catalog row shows which source it came from. When you correct a product, the correction applies to your diary immediately and is reviewed before anyone else sees it.

• USDA FoodData Central. The public reference for generic and branded foods in the United States.
• Open Food Facts. Community-maintained product data, credited as © Open Food Facts contributors.
• Your foods. Anything you add from a label lives in your own catalog and syncs with your account.

What if you ate half a bag instead of one serving?

Change the number, not the product. Every product opens with its serving sizes and a gram field, so half a bag is one edit rather than a guess. The serving printed on a label is rarely what a person actually ate, and the app does not pretend otherwise.

The stepper moves in small increments, so “most of the bag” becomes a number rather than a guess. Saved meals keep the portion, so the sandwich you make every day is one tap.

What happens when a barcode is not in the database?

You add it once from the nutrition label and it is yours from then on. No catalog has every product, especially store brands and regional items. Adding a product takes the panel on the back of the pack, and the next scan of that code finds it immediately.

What you enter is the label itself: name, serving, calories, macros. It stays in your foods and scans instantly from then on, and you can offer it to the shared catalog for review.

Does barcode scanning work without an internet connection?

Reading the code always works offline, because it happens on the phone. Matching it to a product uses the catalog stored on your device first, so foods you have scanned before still resolve on a plane or in a basement. New products need a connection once.

The online catalog is only consulted when the product is not on your phone yet. Photo scans are the only kind of logging that always needs a connection.

Is barcode scanning free in CalorieCounter?

Yes, free on every plan with no daily limit, and it will stay that way. Several popular trackers have moved barcode scanning into a paid tier. It is the fastest and most exact way to log anything with a label, which is a strange thing to charge for.

We want you to use it. See everything that stays free.

Sources

• Open Food Facts, the open database behind packaged products
• USDA FoodData Central, the reference database behind generic foods