Calorie Calculator

Most people eat 200–500 calories more than they need each day — not because they are greedy, but because they are guessing. This calculator uses the Mifflin-St Jeor equation, the most clinically validated formula for estimating daily calorie needs, to give you a personalized number based on your actual body stats and activity level.

Note: This tool provides estimates for general informational purposes. Consult a registered dietitian or physician before making significant changes to your diet, especially if you have a medical condition.

What Your Numbers Actually Mean

Here is a concrete example before you enter your own data. A 35-year-old woman, 165 cm, 65 kg, working a desk job with no regular exercise:

• BMR: 1,399 calories (what her body burns doing absolutely nothing)
• TDEE (sedentary): 1,679 calories (her actual daily burn)
• To lose 1 lb/week: 1,179 calories/day
• To maintain weight: 1,679 calories/day
• To gain 1 lb/week: 2,179 calories/day

Now the same woman if she exercises moderately 3–5 days per week:

• TDEE (moderately active): 2,184 calories
• To lose 1 lb/week: 1,684 calories/day

The difference between sedentary and moderately active is 505 calories per day — that is roughly a 30-minute jog. This is why activity level matters so much in your calculation.

The Mifflin-St Jeor Formula (With Worked Example)

This calculator uses the Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition (1990) by Mifflin MD et al. Multiple independent studies have confirmed it as the most accurate BMR predictor for the general population.

For men:

BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5

For women:

BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Worked example for a 28-year-old man, 180 cm, 80 kg:

• BMR = (10 × 80) + (6.25 × 180) − (5 × 28) + 5
• BMR = 800 + 1,125 − 140 + 5
• BMR = 1,790 calories
• Lightly active (1.375): TDEE = 1,790 × 1.375 = 2,461 calories/day

Understanding BMR vs TDEE: Why the Difference Matters

BMR is the floor. It is the calories your body burns just to stay alive: breathing, circulation, organ function, body temperature. If you lay completely still in bed for 24 hours, you would burn your BMR in calories.

TDEE is your actual daily burn. It includes all movement — walking to your kitchen, fidgeting, exercising, carrying groceries. TDEE = BMR × activity multiplier.

Here is the important insight most people miss: for sedentary desk workers, TDEE is only about 20% above BMR. Exercise matters, but even daily gym sessions only add a 50–70% increase to your BMR, not 200–300% as some fitness content implies. This is why what you eat has more impact on weight than exercise alone.

Activity Level Multipliers — Pick the Right One

Important: Most people overestimate their activity level. If you exercise 3 times per week but otherwise sit at a desk and drive everywhere, choose "Lightly active," not "Moderately active." When in doubt, pick one level lower than feels right — it is easier to adjust upward if you are not losing weight than to discover you have been over-eating for months.

Goal Adjustments: How Calories Are Modified

Once your TDEE is calculated, the tool adjusts your daily calorie target based on your goal:

• Lose weight: A 500 calorie/day deficit from TDEE. This creates approximately 1 lb (0.45 kg) of fat loss per week — a widely accepted safe rate. The minimum floor is 1,200 calories (women) / 1,500 calories (men).
• Maintain weight: TDEE is your target. No adjustment applied.
• Gain weight: A 500 calorie/day surplus above TDEE. This supports approximately 1 lb of weight gain per week, though actual muscle gain will be slower and depends heavily on resistance training and protein intake.

Macronutrient Breakdown

After calculating your daily calorie target, the calculator distributes calories across three macronutrients using a balanced general-purpose ratio:

• Protein: 30% — converted to grams using 4 calories per gram
• Carbohydrates: 40% — converted to grams using 4 calories per gram
• Fat: 30% — converted to grams using 9 calories per gram

This 30/40/30 split is a reasonable general starting point, but it is not universally optimal. Athletes, those following low-carb or ketogenic diets, people with type 2 diabetes, and anyone with specific medical conditions may need significantly different ratios. Consult a registered dietitian for personalized macronutrient guidance.

Example for a 1,800 calorie daily target:

• Protein: 540 cal ÷ 4 = 135g protein/day
• Carbohydrates: 720 cal ÷ 4 = 180g carbs/day
• Fat: 540 cal ÷ 9 = 60g fat/day

How to Use This Calorie Calculator

1. Enter your age (15–100 years)
2. Select your gender — the Mifflin-St Jeor formula uses different constants for men and women
3. Enter your weight in kilograms (30–300 kg; decimal values accepted)
4. Enter your height in centimetres (100–250 cm)
5. Select your activity level — use the table above to pick honestly
6. Select your goal — lose, maintain, or gain weight
7. Click Calculate — results appear instantly with BMR, TDEE, daily target, and macros
8. Download CSV — export your results to track progress over time

Why Your Calorie Target Is an Estimate, Not a Prescription

All BMR formulas, including Mifflin-St Jeor, produce estimates with a margin of error of roughly ±10–15%. Individual metabolic rates vary due to genetics, hormonal status, muscle-to-fat ratio, medications, and gut microbiome. Two people with identical stats can have meaningfully different actual calorie needs.

Use this calculator as a starting point. Track your weight over 2–3 weeks and adjust by 100–200 calories up or down based on actual results. That empirical adjustment will be more accurate than any formula.

Disclaimer: This tool provides general health information only. It is not a substitute for professional medical or dietary advice. If you have a health condition affecting your metabolism or nutritional needs, consult a qualified healthcare provider before changing your diet.

Calorie Calculator FAQs

How many calories should I eat to lose weight?

To lose approximately 1 pound (0.45 kg) per week, eat 500 fewer calories per day than your TDEE. Select "Lose Weight" as your goal and this calculator applies that deficit automatically. Going below 1,200 calories/day (women) or 1,500 calories/day (men) is generally not recommended without medical supervision, as it increases the risk of nutrient deficiency and muscle loss.

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) is your actual daily burn, including all physical activity. For most sedentary adults, TDEE is only 20% above BMR — exercise increases it further. Your goal calorie target is calculated from TDEE, not BMR.

Which formula does this calculator use?

The Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition (1990). It is the most widely validated formula for general BMR estimation. Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: same but −161 instead of +5.

Is 1,200 calories a day enough?

1,200 calories/day is the typical minimum floor for women on a weight-loss diet (1,500 for men). Below this level, it becomes very difficult to meet protein, vitamin, and mineral requirements. If your calculated target is near or below these numbers, speak to a dietitian before proceeding.

Why am I not losing weight even at the calculated calorie target?

Several factors can explain this: you may be overestimating your activity level (try dropping one level), your portion sizes may be larger than estimated, or you may be experiencing water retention that masks fat loss. Give any calorie target at least 3 full weeks before adjusting — short-term weight fluctuations are normal.

Does the calculator account for age-related metabolic changes?

Yes. The Mifflin-St Jeor formula includes age as a variable — older individuals naturally have lower BMR values. However, all formulas become less accurate at the extremes of age. For children under 15 or older adults with significant medical histories, consult a healthcare professional for personalized guidance.