Enter your sex, age, height, weight and activity level to estimate your resting metabolic rate (RMR), your total daily energy expenditure (TDEE), and simple calorie targets for losing or gaining weight. It is a starting point for diet and fitness planning, not medical advice.
How it works
The calculator uses the Mifflin-St Jeor equation, the most validated predictive formula for resting metabolism. With weight in kg, height in cm, and age in years:
- Men: RMR = 10 × kg + 6.25 × cm − 5 × age + 5
- Women: RMR = 10 × kg + 6.25 × cm − 5 × age − 161
It then multiplies RMR by an activity factor (1.2 sedentary to 1.9 very active) to get TDEE, the calories needed to maintain your weight. Finally it offers calorie targets by adjusting TDEE by ±250 kcal/day for a gentle ~0.25 kg per week change.
Illustrative example
A 30-year-old man, 80 kg, 180 cm, moderately active:
- RMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal/day
- TDEE = 1,780 × 1.55 ≈ 2,759 kcal/day
- Mild loss = 2,759 − 250 ≈ 2,509 kcal/day
- Mild gain = 2,759 + 250 ≈ 3,009 kcal/day
| Activity level | Multiplier | Typical profile |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Light | 1.375 | Light exercise 1-3 days/week |
| Moderate | 1.55 | Moderate exercise 3-5 days/week |
| Active | 1.725 | Hard exercise 6-7 days/week |
| Very active | 1.9 | Physical job plus training |
Choosing your activity level honestly
Most people underestimate how sedentary they are and overestimate how active they are. The most common mistake is selecting “moderate” because they go to the gym three times a week while spending eight hours a day at a desk. A more accurate picture: if the only deliberate exercise you do is three 45-minute gym sessions per week and you otherwise sit all day, “light” (1.375) is probably a better fit than “moderate.” This matters because the TDEE difference between light and moderate is around 200–250 kcal/day — roughly equal to the deficit or surplus the calorie targets are built on.
How to use the calorie targets
The targets are built on a 250 kcal/day adjustment, which corresponds to roughly 0.25 kg (half a pound) per week of gain or loss. This is a conservative, sustainable rate that is less likely to cause muscle loss during weight reduction or excessive fat gain during a bulk compared to more aggressive deficits or surpluses.
The key discipline is treating the output as a starting estimate and then tracking actual results over two to four weeks. If your weight is not changing at the intended rate, adjust your intake or re-check your activity level rather than assuming the equation is wrong. All predictive equations carry individual variation — the Mifflin-St Jeor is the most accurate published formula for population-level estimates, but individual metabolic rates can differ from predictions.
Practical considerations
- RMR is not the same as what you burn lying still. Sitting, digesting food (the thermic effect), and low-level movement all add to what you actually expend. RMR is the floor, not the ceiling of resting expenditure.
- Age reduces RMR partly through lean-mass changes. The equation captures this through the age term, but people who maintain muscle mass through resistance training often have higher-than-predicted metabolic rates.
- Illness, medications, and thyroid conditions can shift actual metabolism substantially. If your weight is not responding as expected despite consistent tracking, a conversation with a healthcare professional is worthwhile.
Everything is calculated privately in your browser; actual metabolism varies with body composition and genetics.