How this calorie calculator works
The first step is your basal metabolic rate (BMR), the energy your body uses at complete rest. BMR is a value, not a formula, and it can be estimated in several ways. This calculator uses the Mifflin-St Jeor equation, the equation most commonly used today for estimating BMR in adults. It generally performs better than older equations such as Harris-Benedict, though it remains an estimate rather than a measurement.
Men: 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5
Women: 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161
Your maintenance calories are that BMR multiplied by an activity factor, which accounts for movement, training and daily life. These are the five levels used here:
| Activity level | Multiplier | Who it fits |
|---|---|---|
| Sedentary | 1.2 | Little or no regular exercise |
| Lightly active | 1.375 | Light exercise 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Extra active | 1.9 | Very hard training, physical job or two sessions a day |
To lose weight, the calculator takes a percentage off maintenance: 10 percent for a gentle deficit, 15 percent for a moderate one, 20 percent for a higher one. If your maintenance estimate is 2,000 calories a day, a 15 percent deficit gives a daily target of about 1,700 calories. Weight-gain targets work the same way in reverse, adding 5, 10 or 15 percent.
The macro split is built from your body weight rather than from fixed percentages. Protein is set at 1.6 g per kilogram of body weight and fat at 0.8 g per kilogram; carbohydrates take whatever calories are left in the daily target. If protein and fat alone would exceed the target, fat drops to 0.6 g per kilogram so the carbohydrate figure stays workable.
The same numbers you get in the app
This page uses the same calculation logic as the GATA app. BMR is estimated with the same Mifflin-St Jeor equation, the activity levels are the same, and the deficit options map to the same daily targets. The number you see here is the starting target the app will set for you, not a separate marketing estimate.
Two things can differ. Rounding and any settings you adjust in the app can shift the figure slightly. More importantly, the app keeps the target current: as your logged weight changes, your daily target is recalculated, while this page gives you one starting point at your weight today.
How accurate is a calorie calculator?
Every calorie calculator produces a population-level estimate. The equations were built by measuring many people and describing the average, so the result tells you what someone with your age, height, weight and sex typically needs. It does not measure you.
Individual energy expenditure varies for reasons no equation can see: body composition, how much you move without noticing, sleep, medication, and how accurately anyone estimates their own activity level. Two people with identical inputs can genuinely need different amounts.
The useful move is to treat the number as a starting point and check it against reality. Log your food for two to three weeks, watch the weekly average of your weight rather than single days, and adjust the target by a small amount if the trend is not going where you want. No calculator measures a specific person's metabolism, but your own weight trend does the job over time.
Frequently asked questions
Turning the number into a daily habit
The hard part is not the target. It is recording what you eat on an ordinary Wednesday, after work, when the meal was cooked at home and nothing has a label. A target you never compare with real intake cannot tell you anything.
That is what GATA is for. You log a meal from a photo, and a full plate with several foods on it is recognised as separate items with their own calories, so you are not entering ingredients one by one. Your daily target updates as your weight changes. GATA AI Pro is a subscription; new users can start with a 3-day free trial, once per user. There is no free plan.
Related reading
- BMI calculator
- GATA: AI calorie tracker and weight loss app
- Calorie calculator for women: daily calories by age, activity and goal
- Maintenance calorie calculator: how many calories do you need to maintain weight?
- Best protein tracker app: track protein and macros from one photo
- Am I eating okay? 7 signs your eating pattern is working