Free Calorie Calculator
Calculate your daily calorie needs using the Mifflin-St Jeor equation — the most accurate BMR formula available. Enter your age, sex, weight, height, and activity level to get your BMR and TDEE for weight loss, maintenance, or muscle gain. Free, private — all calculations run in your browser.
Calorie Targets by Goal
| Goal | Calories/day | Weekly Change | vs TDEE |
|---|---|---|---|
| Extreme Loss | 1,301 | -2.0 lbs/wk | -1000 kcal |
| Weight Loss | 1,801 | -1.0 lbs/wk | -500 kcal |
| Mild Loss | 2,051 | -0.5 lbs/wk | -250 kcal |
| Maintain | 2,301 | ±0 lbs/wk | Maintenance |
| Mild Gain | 2,551 | +0.5 lbs/wk | +250 kcal |
| Muscle Gain | 2,801 | +1.0 lbs/wk | +500 kcal |
What These Numbers Mean
- BMR (1,674 kcal) is the energy your body burns at complete rest — breathing, circulation, and organ function. You would burn this many calories even if you stayed in bed all day.
- TDEE (2,301 kcal) is your Total Daily Energy Expenditure — BMR scaled by your activity level (×1.375). Eat at TDEE to maintain your current weight.
- A 500 kcal/day deficit produces ~1 lb of fat loss per week. A 1,000 kcal/day deficit yields ~2 lbs/week (generally the safe maximum). Extreme deficits risk muscle loss and nutrient deficiencies.
- The Mifflin-St Jeor equation (1990) is considered the most accurate predictor of resting metabolic rate for most people, outperforming the older Harris-Benedict (1919) formula in clinical validation studies.
About This Calorie Calculator
This free calorie calculator uses the Mifflin-St Jeor equation — published in 1990 and validated in multiple peer-reviewed studies as the most accurate method for estimating Basal Metabolic Rate (BMR) in healthy adults. A 2005 review in the Journal of the American Dietetic Association found the Mifflin-St Jeor equation to be the most reliable formula for most non-obese individuals, consistently outperforming the older Harris-Benedict equation (1919) in accuracy.
The Formula — BMR and TDEE
The calculator first computes your Basal Metabolic Rate (BMR) — the calories your body requires at complete rest to maintain essential functions like breathing, circulation, temperature regulation, and cell repair.
Females: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
The BMR is then multiplied by an activity factor to give your Total Daily Energy Expenditure (TDEE) — the actual calories you burn on a typical day including all physical activity:
Lightly active (1–3 days/week): TDEE = BMR × 1.375
Moderately active (3–5 days/week): TDEE = BMR × 1.550
Very active (6–7 days/week): TDEE = BMR × 1.725
BMR vs TDEE — Which Number Matters?
BMR tells you the minimum calories your body needs to survive at rest — it is a useful reference point but not a diet target. TDEE is the number you should use for meal planning. Eating at TDEE = weight maintenance. Eating 300–500 calories below TDEE = gradual fat loss (roughly 0.3–0.5 kg per week). Eating 200–350 calories above TDEE = lean muscle-building (assuming adequate protein and resistance training).
It is important to note that your TDEE is not fixed — it changes as your weight, age, and activity level change. A person who loses 10 kg will have a lower TDEE than when they started, even if everything else remains the same. Recalculating every 4–8 weeks as you progress is recommended practice.
Why Mifflin-St Jeor and Not Harris-Benedict?
The Harris-Benedict equation was developed in 1919 using a small sample of mostly young, lean men. While widely used for decades, it tends to overestimate BMR by 5–15% compared to modern indirect calorimetry measurements. The Mifflin-St Jeor equation, derived from a larger and more diverse dataset in 1990, has been validated in multiple independent studies and is now recommended by the Academy of Nutrition and Dietetics as the preferred method for estimating calorie needs in healthy adults.
Limitations and What the Calculator Cannot Account For
The Mifflin-St Jeor equation is an estimate based on population averages. It cannot account for:
- •Individual metabolic variation — two people with identical stats can have BMRs differing by 15%
- •Hormonal conditions such as hypothyroidism, PCOS, or Cushing's syndrome that significantly alter metabolism
- •Medications that affect metabolic rate (corticosteroids, beta-blockers, antidepressants)
- •Pregnancy and breastfeeding, which substantially increase calorie needs
- •Very high muscle mass (may underestimate needs) or very high body fat (may overestimate needs)
- •Adaptive thermogenesis — the metabolic slowdown that occurs after weeks in a sustained calorie deficit
Privacy Notice
All calculations run entirely in your browser. No data you enter — including your weight, height, age, or sex — is transmitted to any server or stored anywhere. Your information stays completely private on your device.
When to Use This Calculator
Find your TDEE and subtract 300–500 calories to create a sustainable calorie deficit without triggering extreme hunger or muscle loss.
Calculate your maintenance calories, then add 200–350 calories above TDEE for a lean bulk that minimises fat gain while supporting muscle growth.
See how increasing your activity level to "very active" changes your calorie needs — essential for fuelling long training runs without bonking or losing muscle.
During recovery, calorie needs increase to support healing. Use this calculator as a baseline and work with your dietitian to set an appropriate recovery target.
Run the calculator twice with different activity levels to see the exact calorie difference — a useful way to understand how much exercise actually contributes to your energy budget.
💡 Pro Tips
Track your food intake for two weeks without changing your diet first. This reveals your true current calorie intake and lets you compare it to your TDEE. Most people are surprised — under-reporters typically eat 20–40% more than they think, while dieters often eat far less than they realize and then plateau because the body adapts.
Aim for 1.6–2.2 grams of protein per kilogram of body weight during a calorie deficit. High protein intake preserves lean muscle mass, which keeps your basal metabolic rate from dropping as much during weight loss. It also keeps you fuller longer, making the deficit easier to sustain.
Account for adaptive thermogenesis. After 8–12 weeks in a sustained calorie deficit, your body reduces its metabolic rate by 10–15% beyond what simple weight loss would predict. This is why fat loss slows or stalls. A 1–2 week diet break at maintenance calories can reset hormones and partially reverse this adaptation.
NEAT (Non-Exercise Activity Thermogenesis) — fidgeting, walking, standing, household chores — can account for 15–50% of total daily energy expenditure and varies enormously between individuals. Two people with identical bodies and formal exercise routines can have TDEE values differing by 500–800 calories based on NEAT alone. If you have an active job or rarely sit still, choose "lightly active" or higher.
Frequently Asked Questions
Medical Disclaimer
Calorie Calculator — Results are estimates based on the Mifflin-St Jeor equation and do not constitute medical or nutritional advice. Individual calorie needs vary based on factors this calculator cannot measure, including hormonal status, medications, and medical conditions. Before making significant dietary changes — especially if you have diabetes, kidney disease, an eating disorder history, or are pregnant — consult a registered dietitian or your healthcare provider.
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