Calorie Calculator

About the Calories Calculator

Daily calorie needs depend on your body size, age, sex, and how active you are — and your goal (losing, maintaining, or gaining weight) shifts that number further. This calculator estimates your baseline metabolic rate and adjusts it for activity and goal to give you a practical daily calorie target.

How It Works

The calculator first computes your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest — using the Mifflin-St Jeor equation, widely regarded as one of the most accurate BMR formulas available. It then multiplies BMR by an activity factor matching your selected activity level to estimate Total Daily Energy Expenditure, and applies a 500-calorie adjustment up or down if your goal is weight loss or gain.

BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + (5 for male, −161 for female); TDEE = BMR × activity factor; Goal adjustment ±500 kcal.

Worked example

Scenario: A 30-year-old man, 70 kg and 175 cm, moderately active, aiming to maintain weight.

1. BMR (Mifflin-St Jeor): 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,648.75 kcal.
2. Multiply by the moderate activity factor: 1,648.75 × 1.55 = 2,555.6 kcal.
3. Goal 'maintain' adds nothing, so the estimate is about 2,556 kcal a day.
4. Choosing 'lose' would subtract 500 kcal (about 2,056 kcal).

Result: About 2,556 kcal a day to maintain weight — an estimate, not a prescription.

Tips and common mistakes

• A 500 kcal daily deficit is a common starting point and corresponds to roughly 0.5 kg (1 lb) a week, but real results vary.
• The calculator flags targets below 1,200 kcal (women) or 1,500 kcal (men); intakes that low should be supervised by a professional.
• Recheck every few kilograms of weight change, because your energy needs change too.
• Pregnancy, breastfeeding, medical conditions and eating-disorder history need individual advice rather than a formula.

Assumptions & Limitations

• Uses a standard ±500 calorie per day adjustment for weight loss or gain, which corresponds to roughly one pound of change per week.
• The Mifflin-St Jeor equation is applied uniformly across all adult ages and body types.

• Individual metabolism varies due to genetics, muscle mass, and health conditions, so actual needs may differ from this estimate by a meaningful margin.
• Not intended for children, pregnant or breastfeeding individuals, or people with certain medical conditions affecting metabolism.

A safer way to use calorie estimates

This calculator uses a formula-based BMR estimate, an activity multiplier and a simple calorie adjustment for the selected goal. The result is a planning estimate—not a prediction of exactly how quickly body weight will change. NIH research on body-weight dynamics notes that the traditional fixed “3,500 calories equals one pound” rule does not fully account for the way metabolism and energy expenditure adapt over time.

Adults with medical conditions, a history of disordered eating, or special nutritional needs should use individualized professional guidance. This calculator is not intended for children or for pregnancy or breastfeeding.

Sources and review

Method: BMR from the Mifflin-St Jeor equation, multiplied by a standard activity factor (1.2–1.9), with ±500 kcal for a weight-change goal.

Sources:

• Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990;51(2):241–247.
• FAO/WHO/UNU expert consultation on human energy requirements (physical activity level concept, 2001/2004).

Last reviewed: October 2026 by Faheem Ali, founder of CalculatorAnything. The method and examples are provided for transparency; results remain estimates and may contain errors.

Results are estimates for general information and screening, not a diagnosis or medical advice. Talk to a qualified healthcare professional before making health or diet decisions. Spotted an error? Tell us — see our editorial policy for how corrections are handled.

Frequently Asked Questions