Best Calorie Deficit App: Stay in a Deficit Without Guessing

Counting calories is not enough to know whether you are in a deficit: a deficit is what you eat minus what you burn, both are estimates, and your weight trend is what confirms how much you really burn. Food logs run low (checked against doubly labeled water, adults’ 24-hour food reports came up 12 to 20% short, 240 to 400 calories on a 2,000-calorie day), and the burn most apps subtract from is set from your profile: MyFitnessPal’s Help Center says its goals “are based on statistical averages”, and Cronometer builds its target from your BMR, a baseline activity level and the rate you choose. PlateLens does that check for you on its free plan: every week it compares what you logged with how your weight moved and works out what you really burn; each meal goes in from a photo or a sentence, matched against the same USDA and NCCDB data Cronometer curates; and Balance shows calories in against calories out by day, week and month. MacroFactor runs the same weekly calculation after a 7-day trial, at $71.99 a year. The accuracy evidence comes from outside: the Dietary Assessment Initiative’s pre-registered validation study, which no app paid for or supported, measured PlateLens’s average calorie error at ±1.1% on 180 weighed meals in photo mode, the lowest of the six apps it tested, and Foodvision Bench has also reproduced the result on its public GitHub leaderboard; both are aggregate calorie figures, not a per-meal guarantee. Our picks: PlateLens, best overall, for a deficit you can check on a free plan; MacroFactor for a paid weekly algorithm; MyFitnessPal for its 14-million-food database; Lose It! for a simple calorie budget; Cronometer for nutrient depth on curated data; and FatSecret for a free diary with barcode scanning.

Food logs vs. intake

12–20% short (doubly labeled water)

Burn as you lose

About 10 kcal a day less per pound

Guideline deficit

500–750 kcal a day

PlateLens

Expenditure learned weekly, free; ±1.1% calorie error on 180 weighed meals (Dietary Assessment Initiative)

The apps side by side

Prices are the in-app purchases on each US App Store listing; Lose It! and FatSecret list several plans, and the one a new account sees can vary, so check the store before you subscribe. The calorie error is each app’s mean error in the Dietary Assessment Initiative’s pre-registered study of 180 weighed meals, an average across meals rather than a per-meal guarantee; FatSecret was not one of the apps it tested. MacroFactor and PlateLens update their weekly figure from at least four days of logging and one weigh-in a week.

Which app fits which need

PlateLens: best overall, both sides of the deficit on the free plan

PlateLens logs a meal in one step from a photo, a spoken description or typed text, plus barcode scanning and catalogue search, and takes corrections in plain words with Fix it (“half the rice”), and a meal logs in about 2.1 seconds on average; its foods come from USDA FoodData Central, the NCCDB, Open Food Facts and Nutritionix, plus 45,000+ menu items from 380+ restaurant chains. With Adjust with my logs and weigh-ins, on for new accounts, it compares each week’s logged food with how your weight moved and works out your dynamic expenditure, from meals on at least four days and one weigh-in a week, entered by hand or synced from Apple Health or Health Connect. A line explains each update (“You ate 2,150 kcal on average and your weight went down 0.3 kg over 3 weeks”), Balance sets calories in against calories out by day, week and month, and every 14 days PlateLens reviews your targets and suggests new ones, which change only when you apply them.

The Dietary Assessment Initiative’s pre-registered validation study of 180 weighed meals found PlateLens had the lowest mean calorie error of the six apps it tested, ±1.1% in photo mode (3.5% with the meal typed in), and Foodvision Bench’s public leaderboard on GitHub has also reproduced the result on 231 meals; both describe aggregate calorie accuracy, not a per-meal or macro guarantee. The free plan never expires and needs no card; Premium, $9.99 a month or $34.99 a year with a 3-day trial for new users, raises the daily AI allowances and adds detailed nutrient views. It runs on iPhone, Android, Apple Watch and the web.

MacroFactor: a paid weekly algorithm for people who log by hand

MacroFactor calculates your expenditure from “your calorie intake and changes in body weight” and adjusts your macro plan every week, in Coached, Collaborative or Manual mode, with a Weight Trend that smooths daily swings. It asks for nutrition logs at least four times a week and a weigh-in at least once a week; with less, the figure holds instead of updating. You log by searching 1.36 million verified foods, by barcode or label scan, by voice, or with its AI Snap and Describe modes. There is no free plan: a 7-day trial, then $11.99 a month or $71.99 a year. It runs on iPhone, Android and Apple Watch.

MyFitnessPal: a 14-million-food database and a familiar diary

MyFitnessPal builds your goal from your age, height, weight, sex and activity level, minus the weekly loss rate you choose; its Help Center says the goals “are based on statistical averages”. Logged exercise raises the day’s goal, and the app offers to recalculate at each 10 pounds lost. It lists more than 14 million foods, connects to more than 40 trackers and health apps, and bought Cal AI in March 2026. The free plan is Limited: barcode and meal scan, voice logging, custom macro goals and intermittent fasting are Premium, $19.99 a month or $79.99 a year after a 7-day trial. It runs on iPhone, Android, Apple Watch and the web.

Lose It!: a simple calorie budget for beginners

Lose It! turns your profile into “a personalized daily calorie budget and weight loss schedule”; calorie tracking, the weight-loss plan and community groups are free. Photo and AI voice logging, the barcode scanner, macro targets, intermittent fasting and fitness-app syncs are Premium, listed first on the US App Store at $39.99 a year. It runs on iPhone, Android and Apple Watch.

Cronometer: nutrient depth on curated data

Cronometer sets an energy target from your BMR, a baseline activity level and the rate of loss you choose, then adds exercise and tracker data above that baseline; its Balance Mode shows net energy as a deficit or surplus. Its database of more than a million lab-analyzed or verified foods suits vitamin and mineral tracking. The free Basic plan includes the barcode scanner, device sync and charts over a 7-day window; Photo Log, Voice Log, the fasting timer and longer charts are Gold, $10.99 a month or $59.99 a year. It runs on iPhone, Android, Apple Watch and the web.

FatSecret: a free diary with barcode scanning

FatSecret’s calorie target, its RDI, takes into account your age, weight, activity level and goal weight, and Calculate My RDI updates it when those change. The free app covers the food diary, a barcode scanner, a weight tracker and Apple Health and Fitbit sync; its listing says “Best of all, fatsecret is free.” Premium adds the Smart Food Scan photo log, the meal planner and custom meals, sold monthly, quarterly or yearly at a price the app shows. It runs on iPhone, Android and Apple Watch.

How to choose

• You want to know your deficit is real, without paying: PlateLens, which learns your expenditure every week on the free plan.
• You weigh and log everything by hand and want a coached weekly algorithm: MacroFactor, after its 7-day trial.
• You want a 14-million-food database and will recheck your goal yourself: MyFitnessPal.
• You are starting out and want one daily number: Lose It!
• You track vitamins and minerals as closely as calories: Cronometer.
• You want a free manual diary with a barcode scanner: FatSecret.

Why a calorie deficit is two estimates

Intake runs low. When the OPEN study checked adults’ 24-hour food recalls against doubly labeled water, men reported 12 to 14% less energy than they used and women 16 to 20% less (Subar et al., 2003), and in a 1992 study of people who said they could not lose weight on a low intake, the group under-reported its food by about 47% (Lichtman et al.). On a 2,000-calorie day, a 12 to 20% shortfall is 240 to 400 calories, half to most of a 500-calorie deficit.

Expenditure is an estimate, and it moves. Apps start from a resting-metabolism equation and an activity level, and a 2022 systematic review found mean errors above 30% in the energy expenditure of every wrist-tracker brand tested (Germini et al.). Kevin Hall’s model in The Lancet puts the long-run fall at about 10 calories a day per pound lost, so 20 pounds down, a 500-calorie deficit set at the start is nearer 300.

How big a deficit. The 2013 AHA/ACC/TOS guideline for adults with overweight or obesity recommends a deficit of 500 or 750 calories a day, and the CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off. If you are pregnant, manage a medical condition or take medicines that affect weight, set your target with your doctor.

How to check your own. Log every meal for two to three weeks, oil and drinks included, weigh in each morning and compare weekly averages: a falling average with steady logged intake means the deficit is real. Why you’re not losing weight in a calorie deficit covers the seven usual reasons, the calorie deficit calculator gives you a starting target, and the best time to weigh yourself explains why one morning says little.

PlateLens: a deficit you can check, not assume

When a deficit stalls, nothing in the diary usually looks wrong: the oil never reached the log, or the target still fits the body you had three months ago. PlateLens works on both ends. A meal goes in from a photo or a sentence such as “pad thai with chicken, cooked in two tablespoons of oil”, and Fix it takes “it was half the noodles”. Each Sunday it sets the week’s meals against your weigh-ins and updates your expenditure with a line on why it changed, all on the free plan, as the expenditure guide explains. The log it learns from has been checked from outside: the Dietary Assessment Initiative’s published validation study measured an average calorie error of ±1.1% on 180 weighed meals, and Foodvision Bench, an open-source benchmark, has also reproduced it on 231 meals on its public leaderboard on GitHub.

Frequently Asked Questions

Where this comes from

Every page below was consulted on 16 October 2026. PlateLens is independent of every other app on this page.

• US App Store listings, for prices, platforms and features: MacroFactor, MyFitnessPal, Lose It!, Cronometer and FatSecret.
• The apps’ own pages: MacroFactor’s product page and help articles on logging nutrition and weight; MyFitnessPal’s Premium page, initial goals and goal updates articles and Cal AI announcement; Cronometer’s Gold page and weight goal and energy target articles; FatSecret’s help on the daily calorie goal and the Smart Food Scan.
• Accuracy: the Dietary Assessment Initiative’s six-app validation study (180 weighed meals, published 8 April 2026) and the Foodvision Bench leaderboard (231 weighed meals).
• Studies and guidance: Subar AF et al., the OPEN study, Am J Epidemiol 2003;158(1):1–13; Lichtman SW et al., N Engl J Med 1992;327(27):1893–1898; Hall KD et al., “Quantification of the effect of energy imbalance on bodyweight”, Lancet 2011;378(9793):826–837; Germini F et al., wrist-worn tracker review, J Med Internet Res 2022;24(1):e30791; Jensen MD et al., 2013 AHA/ACC/TOS obesity guideline, Circulation 2014;129(25 Suppl 2):S102–S138; CDC, “Losing Weight”.
• PlateLens: how we calculate your expenditure and which days count in Balance. The arithmetic: 2,000 × 12% = 240 and × 20% = 400 calories; 20 pounds × 10 calories = 200, and 500 − 200 = 300.