How the calorie numbers are built
The tool first calculates BMR — the energy your body uses at complete rest — with the Mifflin-St Jeor equation, which factors in weight, height, age, and sex. It then multiplies BMR by an activity factor from 1.2 (sedentary) to 1.9 (extra active) to get TDEE, the calories that keep your weight stable given how much you move. Mifflin-St Jeor is accurate to within about 10% for most people, making it the current standard for calorie estimates.
Turning TDEE into weight-goal targets
Roughly 3,500 calories equal about a pound of body fat, or 7,700 per kilogram. So a daily deficit of 500 calories predicts about a pound of loss per week, and 1,000 predicts about two pounds. The calculator lays these out as goal rows — mild, moderate, and faster loss, plus maintenance and a gain option — so you can pick a pace. It flags any target that dips below roughly 1,200 calories for women or 1,500 for men, which is generally too low to sustain without medical supervision.
Why estimates are a starting point
These equations describe an average person of your stats; your real metabolism depends on muscle mass, genetics, hormones, medications, and how honestly you rate your activity — the most common error. Non-exercise movement, sleep, and stress all shift the number. Treat the result as a starting budget, then adjust based on two to three weeks of real-world results: if the scale isn't moving as predicted, nudge intake up or down by 100–200 calories.
A worked example
A 30-year-old man, 175 cm and 75 kg, moderately active, has a BMR near 1,674 and a TDEE around 2,595 calories per day. To lose about a pound a week he'd aim for roughly 2,095; to lose two pounds a week, about 1,595; to gain a pound a week, about 3,095. Rate yourself sedentary instead and the maintenance figure drops to around 2,009, showing how much activity level alone changes the budget.
Health disclaimer
This calculator provides general guidance only and is not medical advice. Very low calorie intakes can be unsafe, and individual needs vary widely. Consult a qualified healthcare provider or registered dietitian before starting a significant diet, especially if you have a medical condition, are pregnant or breastfeeding, or are under 18.