Mifflin-St Jeor BMR & Calorie Calculator
Use this mifflin calculator to estimate your BMR (Basal Metabolic Rate), maintenance calories, and a practical target for fat loss or muscle gain.
This tool provides estimates. For medical conditions, pregnancy, or performance nutrition, consult a qualified professional.
What is a mifflin calculator?
A mifflin calculator uses the Mifflin-St Jeor equation to estimate how many calories your body burns at rest. This value is called your basal metabolic rate (BMR). Because BMR is one of the best starting points for nutrition planning, this calculator is commonly used as a calorie needs calculator, BMR calculator, and TDEE calculator.
The Mifflin-St Jeor equation
The equation predicts resting energy needs from body size, age, and sex. It is widely used by coaches, dietitians, and fitness apps because it is simple and generally reliable for most healthy adults.
Formula used
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
After BMR is calculated, we multiply it by an activity factor to estimate total daily energy expenditure (TDEE), often called maintenance calories.
How to use this calculator correctly
Step-by-step
- Enter your current age, weight, and height.
- Choose your normal weekly activity level honestly.
- Select your goal: fat loss, maintenance, or lean gain.
- Use the result as a starting target for 2–3 weeks, then adjust based on progress.
Understanding your results
BMR
Your BMR is the energy needed for essential body processes at complete rest (breathing, circulation, organ function).
Maintenance calories (TDEE)
Your TDEE is your estimated daily calorie burn after accounting for activity. If your goal is weight maintenance, this is your best first calorie target.
Goal calories
Goal calories apply a daily adjustment to your maintenance estimate:
- Fat loss: usually 300–700 kcal below maintenance
- Muscle gain: usually 150–350 kcal above maintenance
- Maintenance: around your TDEE
Why your real-world calorie needs may differ
Any calorie calculator is an estimate, not a lab measurement. Your actual needs can vary due to:
- Body composition (muscle mass vs. fat mass)
- Daily movement differences (steps, job demands, fidgeting)
- Hormonal status, sleep quality, and stress
- Food tracking accuracy and portion estimation
The best approach is to use the estimate, track body weight trends weekly, and adjust in small increments.
Practical tips for better results
- Prioritize protein intake each day.
- Keep activity consistent week to week.
- Track body weight under similar conditions (same time, same scale).
- Use a 7-day average to judge trend, not one weigh-in.
- Adjust calories by about 100–200 kcal if progress stalls.
FAQ
Is the Mifflin-St Jeor formula accurate?
For many adults, yes—it performs well as a starting estimate. But individual metabolism differs, so fine-tuning is always necessary.
Can I use this as a weight loss calorie calculator?
Absolutely. Choose the fat-loss option and monitor trends for a few weeks. If weight is not changing, reduce calories slightly or increase activity.
How often should I recalculate?
Recalculate whenever your body weight changes significantly (around 2–5 kg), or when your activity level changes.
Bottom line
This mifflin calculator is a simple way to estimate your BMR, maintenance calories, and calorie target for your goal. Use it as your baseline, then adjust based on real progress. Consistency beats perfection.