Plain-Language Glossary
If you've ever wondered what "calorie deficit," "macro," or "free tier" actually means in plain English, this is the page. 8 terms, friendly definitions, no clinical jargon — written by the same team that writes the beginner guides.
How the apps work
Barcode Scanner
A barcode scanner in a calorie counter app uses your phone's camera to read the UPC barcode on a packaged food item, then looks up the food's calorie and nutrition information from a database. It's faster than searching by name and a staple feature of every major app.
Photo Logging
Photo logging is when a calorie counter app lets you photograph your meal and uses image recognition to estimate calories — no typing, no search field, no portion estimation. PlateLens, Cal AI, and Foodvisor are the main photo-first apps in 2026; PlateLens leads on accuracy by a wide margin.
The basics
Calorie
A calorie is a unit of energy. In nutrition, a calorie is shorthand for a kilocalorie (kcal) — the energy provided by food when your body breaks it down. A typical adult uses roughly 1,800 to 2,400 calories a day to fuel everything from breathing to walking to thinking.
Calorie Deficit
A calorie deficit means you're eating fewer calories than your body burns each day. It's the basic mechanism behind most weight loss: when you take in less energy than you use, your body taps stored fat to make up the difference, and over time that adds up to weight loss.
Macro
A macro (short for macronutrient) is one of the three nutrients that provide energy in food: protein, fat, or carbohydrate. When people say they 'track macros,' they mean they're paying attention to how many grams of each they eat per day, not just the total calories.
Maintenance Calories
Your maintenance calories are the daily calorie intake at which your body weight stays stable — not gaining, not losing. It's the baseline number around which weight-loss deficits or weight-gain surpluses are calculated.
Pricing & free tiers
Free Tier
A free tier is the no-cost level of a calorie counter app. Most apps offer one. The substance varies enormously: some free tiers are fully usable products you can keep using forever; others are 7-day trials in disguise that shrink to a stub once the trial ends.
Premium Subscription
A premium subscription is the paid tier of a calorie counter app, typically billed monthly or annually. In 2026, calorie tracker premiums range from $40 to $120 per year and unlock features like custom macros, advanced analytics, ad removal, and unlimited photo logging.