Calorie Calculator — Daily Calorie Needs and Macronutrients
This calorie calculator estimates how many calories you need per day based on your sex, age, weight, height, activity level, and goal. It first computes your basal metabolic rate (BMR) with the Mifflin-St Jeor equation — the formula most recommended by nutrition professionals — then multiplies it by an activity factor to obtain your total daily energy expenditure (TDEE). From there it adjusts for your goal: maintain, lose, or gain weight.
The result includes a suggested macronutrient breakdown (protein, carbohydrates, and fat) so you can turn a calorie target into an actual eating plan. Keep in mind these are population-based estimates: individual metabolism varies, and factors like muscle mass, medical conditions, and medication can shift real needs. For a personalized plan, consult a registered dietitian or healthcare professional.
How it works
Mifflin-St Jeor BMR — men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; women: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. TDEE = BMR × activity factor (1.2 sedentary to 1.9 very active). Weight loss ≈ TDEE − 500 kcal/day; gain ≈ TDEE + 300–500 kcal/day.
Use cases
- Finding your maintenance calories before starting a diet
- Setting a safe calorie deficit for gradual weight loss
- Planning a calorie surplus for muscle gain alongside strength training
- Translating a calorie target into grams of protein, carbs, and fat
- Adjusting intake after a change in activity level or body weight
- Comparing energy needs across different activity scenarios
Frequently asked questions
How many calories should I eat per day?
It depends on your BMR and how active you are. The calculator multiplies your Mifflin-St Jeor BMR by an activity factor from 1.2 (sedentary) to 1.9 (very active) to estimate your maintenance calories, or TDEE. Eating around that number keeps weight stable; eating below it leads to loss and above it to gain. Individual needs vary, so treat the result as a starting point and adjust based on real-world progress.
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is the energy your body burns at complete rest just to keep vital functions running — breathing, circulation, cell repair. TDEE (total daily energy expenditure) adds everything else: daily movement, exercise, and digestion. TDEE is the number that matters for diet planning, and it is calculated as BMR multiplied by an activity factor.
How many calories do I need to cut to lose weight?
A deficit of roughly 500 kcal per day below your TDEE is the common guideline, producing gradual loss of about 0.5 kg (1 lb) per week, since one kilogram of body fat stores roughly 7,700 kcal. Larger deficits are harder to sustain and can cost muscle mass. Avoid dropping below your BMR for extended periods, and consult a healthcare professional before starting an aggressive diet.
Why does the calculator use the Mifflin-St Jeor equation?
Validation studies have found Mifflin-St Jeor to be the most accurate of the common predictive equations for estimating resting energy needs in most adults, which is why the Academy of Nutrition and Dietetics recommends it. Older formulas like Harris-Benedict tend to overestimate slightly. No equation is perfect for everyone — very muscular or very lean individuals may see larger deviations.
How should I split my calories between protein, carbs, and fat?
A widely used reference range is 10–35% of calories from protein, 45–65% from carbohydrates, and 20–35% from fat. Protein has 4 kcal per gram, carbs 4 kcal, and fat 9 kcal, so a 2,000 kcal plan at 30/40/30 means about 150 g protein, 200 g carbs, and 67 g fat. Athletes and people in a deficit often benefit from the higher end of protein; a dietitian can fine-tune the split for your case.