Calculate Your Daily Calorie Needs
Estimate your Total Daily Energy Expenditure (TDEE) -- the calories you burn each day based on your body and activity level.
Understanding BMR and TDEE
What is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions at complete rest. This includes breathing, blood circulation, brain function, and cell production. BMR typically accounts for 60-75% of your total daily calorie burn.
What is TDEE?
Total Daily Energy Expenditure (TDEE) is your total daily calorie burn, including all physical activity. It's calculated by multiplying your BMR by an activity factor. TDEE represents your "maintenance calories" -- eating this amount should keep your weight stable.
The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor equation, developed in 1990 and considered more accurate than older formulas like Harris-Benedict. The formula is:
For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
The result is then multiplied by an activity factor (1.2 to 1.9) to get your TDEE.
1. Calculate BMR:
BMR = (10 x 60) + (6.25 x 165) - (5 x 30) - 161BMR = 600 + 1031.25 - 150 - 161 = 1,320 kcal2. Apply activity factor (moderate = 1.55):
TDEE = 1,320 x 1.55 = 2,046 kcal/dayThis person needs approximately 2,046 calories per day to maintain their current weight.
Activity Level Multipliers
The activity factor adjusts your BMR based on how physically active you are throughout the day:
| Activity Level | Description | Factor |
|---|---|---|
| Sedentary | Desk job, little to no exercise | 1.2 |
| Lightly Active | Light exercise 1-3 days/week | 1.375 |
| Moderately Active | Moderate exercise 3-5 days/week | 1.55 |
| Very Active | Hard exercise 6-7 days/week | 1.725 |
| Extremely Active | Intense daily exercise + physical job | 1.9 |
Tip: Most people overestimate their activity level. If you're unsure, start with one level lower than you think and adjust based on real-world results over 2-4 weeks.
Calorie Targets for Different Goals
Weight Loss
To lose weight, you need to create a calorie deficit -- eating fewer calories than your TDEE. A deficit of 500 calories per day theoretically leads to about 0.45 kg (1 lb) of weight loss per week. Larger deficits can speed weight loss but may be harder to sustain and could affect muscle mass.
Weight Maintenance
Eating at your TDEE should maintain your current weight. In practice, small daily variations are normal -- the goal is to average near your TDEE over time.
Weight Gain
To gain weight (whether muscle or overall mass), eat more than your TDEE. A surplus of 250-500 calories per day, combined with strength training, typically leads to lean muscle gain. Larger surpluses often result in more fat gain.
Important Considerations
- These are starting points -- track your weight over 2-4 weeks and adjust calories based on results
- Weight fluctuates daily due to water, food volume, and other factors -- look at weekly averages
- Calorie needs change as your weight changes -- recalculate every 5-10 kg (10-20 lbs) lost or gained
- Very low calorie diets (under 1,200 for women, 1,500 for men) should only be followed under medical supervision
Limitations of Calorie Calculators
While the Mifflin-St Jeor equation is well-validated, all calorie calculators have limitations:
- Body composition: The formula doesn't account for muscle vs. fat. Two people with the same weight can have very different metabolic rates
- Genetics: Metabolic rate can vary by 5-10% between individuals of similar size
- Hormones: Thyroid function, menstrual cycle, and other hormonal factors affect metabolism
- Adaptive metabolism: Your metabolism can slow during extended calorie restriction
- Non-exercise activity: Fidgeting, posture, and unconscious movement (NEAT) vary widely between people
Use calculator results as a starting point, then fine-tune based on how your body actually responds over time.
Privacy & Limitations
- All calculations run entirely in your browser -- nothing is sent to any server.
- Results are estimates and should not replace professional medical advice.
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Calorie Needs Calculator FAQ
What is BMR (Basal Metabolic Rate)?
BMR is the number of calories your body burns at complete rest to maintain basic functions like breathing, circulation, and cell production. It represents the minimum energy needed to keep your body alive if you did nothing but rest for 24 hours.
What is TDEE (Total Daily Energy Expenditure)?
TDEE is your total daily calorie burn including all activities. It's calculated by multiplying your BMR by an activity factor. TDEE represents your maintenance calories — the amount you'd need to eat to maintain your current weight.
Which formula does this calculator use?
This calculator uses the Mifflin-St Jeor equation, which research suggests is the most accurate for estimating BMR in most people. For men, the formula is BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5. For women, it's the same formula but minus 161 instead of plus 5.
How accurate is this calorie estimate?
The Mifflin-St Jeor equation typically estimates BMR within 10% of measured values for most people. However, individual factors like muscle mass, genetics, hormones, and health conditions can affect your actual calorie needs. Use this as a starting point and adjust based on real-world results.
What do the activity levels mean?
Sedentary means little to no exercise (desk job, minimal walking). Light activity is 1-3 days of light exercise per week. Moderate is 3-5 days of moderate exercise. Active means hard exercise 6-7 days per week. Very active is for athletes or people with physically demanding jobs who also exercise.
How do I use this for weight loss?
To lose weight, you typically need to eat fewer calories than your TDEE. A common approach is a 500-calorie daily deficit, which theoretically results in about 0.5 kg (1 lb) of weight loss per week. However, individual results vary, and it's important to consult a healthcare provider before making significant dietary changes.
How do I use this for weight gain?
To gain weight, you need to eat more calories than your TDEE. A surplus of 250-500 calories per day is often recommended for gradual weight gain. Combined with strength training, this can help build muscle rather than just fat.
Why does age affect calorie needs?
Metabolism typically slows with age due to loss of muscle mass and hormonal changes. The formula accounts for this by subtracting 5 calories per year of age. This is why maintaining muscle through exercise becomes more important as you get older.
Does muscle mass affect these calculations?
Yes. Muscle tissue burns more calories at rest than fat tissue. The Mifflin-St Jeor equation doesn't directly account for body composition. People with more muscle mass may have a higher actual BMR than calculated, while those with higher body fat percentages may have a lower actual BMR.
Should I eat my exercise calories back?
This depends on your goals. Your TDEE already factors in your general activity level. If you do additional exercise beyond your usual activity, you may need extra calories to fuel recovery. Athletes and very active people often need to eat more on training days.
What's the minimum safe calorie intake?
General guidelines suggest women shouldn't go below 1,200 calories and men shouldn't go below 1,500 calories without medical supervision. Very low calorie diets can lead to nutrient deficiencies, muscle loss, and metabolic adaptation. Always consult a healthcare provider before starting a restrictive diet.
How often should I recalculate my calorie needs?
Recalculate when your weight changes significantly (every 5-10 kg or 10-20 lbs), when your activity level changes, or every few months if you're actively trying to change your weight. Your calorie needs aren't static.