Understanding how many calories your body needs daily is crucial whether your goal is to lose weight, gain muscle, or maintain your current weight. The Mifflin-St Jeor Calculator is one of the most reliable and widely used tools to estimate your Basal Metabolic Rate (BMR) — the number of calories your body burns at rest — and your Total Daily Energy Expenditure (TDEE), which includes physical activity.
Mifflin St Jeor Calculator
🔍 What is the Mifflin-St Jeor Equation?
The Mifflin-St Jeor Equation is a mathematical formula developed in the 1990s to estimate BMR. It is known for being more accurate than previous equations (such as Harris-Benedict), especially for non-obese individuals.
The formula differs slightly for men and women:
🧮 Mifflin-St Jeor Formula:
- 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
To calculate your Total Daily Energy Expenditure (TDEE), the BMR is multiplied by an activity factor.
⚙️ How the Mifflin-St Jeor Calculator Works
The calculator takes four main inputs:
- Gender (Male/Female)
- Weight (in kilograms or pounds)
- Height (in centimeters or feet/inches)
- Age (in years)
Then, you choose your activity level from the following:
| Activity Level | Multiplier |
|---|---|
| Sedentary (little/no exercise) | 1.2 |
| Lightly active (light exercise/sports 1–3 days/week) | 1.375 |
| Moderately active (3–5 days/week) | 1.55 |
| Very active (6–7 days/week) | 1.725 |
| Extra active (physical job/heavy training) | 1.9 |
✅ The calculator provides:
- Your BMR (Basal Metabolic Rate)
- Your TDEE (calories needed per day to maintain weight)
- Calories for weight loss or gain (optional feature)
📘 Example Calculation
Let’s say:
- Gender: Female
- Age: 30 years
- Weight: 65 kg
- Height: 170 cm
- Activity Level: Moderately active (1.55 multiplier)
Step 1: BMR Calculation
BMR = (10 × 65) + (6.25 × 170) – (5 × 30) – 161
BMR = 650 + 1062.5 – 150 – 161 = 1,401.5 kcal/day
Step 2: TDEE Calculation
TDEE = BMR × Activity Factor = 1401.5 × 1.55 ≈ 2172 kcal/day
So, this woman needs approximately 2172 calories/day to maintain her current weight.
🎯 How to Use the Mifflin-St Jeor Calculator
- Select your gender.
- Enter your weight (kg or lbs).
- Input your height (cm or ft/in).
- Provide your age.
- Choose your physical activity level.
- Click “Calculate” to view your BMR and TDEE.
You can use the results to:
- Plan a calorie deficit for fat loss.
- Set a calorie surplus for muscle gain.
- Maintain weight by aligning intake with your TDEE.
⚖️ Calories for Weight Goals
To adjust your calorie intake based on goals:
- Mild weight loss (0.25–0.5 kg/week): Subtract 250–500 kcal/day from TDEE
- Aggressive weight loss: Subtract 750–1,000 kcal/day (not recommended without supervision)
- Mild weight gain (0.25–0.5 kg/week): Add 250–500 kcal/day to TDEE
💡 Tips for Better Accuracy
- Use accurate body measurements for better results.
- Pick the most honest activity level.
- For weight tracking, reassess BMR/TDEE every 4–6 weeks.
- Combine with macronutrient calculators for better nutrition planning.
- Use in conjunction with wearable trackers for precise daily calorie burn data.
🧾 Benefits of Using the Mifflin-St Jeor Calculator
- ✅ Accurate BMR estimate based on body composition.
- ✅ Trusted by health professionals.
- ✅ Customizable for all activity levels.
- ✅ Useful for weight loss, maintenance, or muscle building.
- ✅ Easy to use and interpret.
🏋️ Who Should Use This Calculator?
- Fitness Enthusiasts: For meal planning and macros.
- Dietitians/Nutritionists: To guide clients.
- Individuals on weight-loss journeys.
- Bodybuilders: For bulking/cutting strategies.
- Medical professionals: For metabolic assessment.
❓ 20 Frequently Asked Questions (FAQs)
1. What does BMR stand for?
Basal Metabolic Rate — the calories your body needs at rest.
2. What is TDEE?
Total Daily Energy Expenditure — BMR multiplied by activity factor.
3. Is Mifflin-St Jeor accurate?
Yes, it is one of the most accurate BMR formulas available today.
4. What’s the difference between Mifflin-St Jeor and Harris-Benedict?
Mifflin-St Jeor is newer and more accurate for modern populations.
5. Can I use pounds and inches?
Yes, many calculators allow automatic conversion.
6. Do I need to update this regularly?
Yes, especially if your weight or activity level changes.
7. Is this calculator useful for weight loss?
Absolutely—it shows how many calories to eat for a deficit.
8. Can I use this for muscle gain?
Yes, you can calculate your maintenance calories and add 250–500 kcal/day.
9. How accurate is the activity multiplier?
It’s an estimate; wearables can help fine-tune it.
10. Can this work for older adults?
Yes, the formula accounts for age.
11. Is there a separate formula for children?
Yes, this calculator is meant for adults. Pediatric versions use different equations.
12. Does this account for muscle vs. fat?
No, it uses total weight, not body composition.
13. Is this used in clinical nutrition?
Yes, it’s a common baseline for dietary plans.
14. What if I’m pregnant?
Use a different calculator—pregnancy affects metabolic rate significantly.
15. Is it good for athletes?
Yes, especially if combined with macronutrient calculators.
16. Can it be used for medical conditions?
Consult a doctor, especially for conditions like thyroid disorders or diabetes.
17. How do I switch from pounds to kg?
Divide pounds by 2.2046 to get kilograms.
18. How often should I update the calculator?
Every time your weight or activity changes significantly.
19. Can I trust the calorie estimates completely?
They are estimates; real-world results may vary.
20. What’s next after calculating TDEE?
Plan your diet based on your goal—cutting, maintaining, or bulking.
🧭 Conclusion
The Mifflin-St Jeor Calculator is a reliable and efficient way to estimate how many calories your body needs daily. Whether you’re aiming for weight loss, gain, or just maintaining your current physique, knowing your BMR and TDEE gives you the power to tailor your diet and activity levels effectively.