Understanding TDEE, BMR, and Daily Calorie Needs
Knowing how many calories your body needs each day is the foundation of any effective nutrition plan, whether your goal is losing fat, building muscle, or simply maintaining a healthy weight. This free calorie calculator uses the Mifflin-St Jeor equation — widely regarded as the most accurate predictive formula for estimating Basal Metabolic Rate — combined with standard activity multipliers to determine your Total Daily Energy Expenditure (TDEE). Everything runs in your browser; no data is uploaded or stored anywhere.
What Is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate is the number of calories your body burns at complete rest just to sustain vital functions — breathing, circulating blood, regulating temperature, and maintaining organ function. BMR typically accounts for 60–75% of your total daily calorie expenditure. It varies based on age, sex, height, and weight: larger bodies and younger individuals tend to have higher BMRs because they have more metabolically active tissue.
The Mifflin-St Jeor Equation
Published in 1990, the Mifflin-St Jeor equation replaced older formulas like Harris-Benedict as the gold standard for BMR estimation. Research has shown it predicts resting metabolic rate within 10% for most adults, making it the formula recommended by the Academy of Nutrition and Dietetics. The equations are:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
The key difference between the male and female formulas is the constant at the end (+5 for men, −161 for women), which reflects the higher average lean body mass found in males. This difference translates to roughly 150–170 fewer baseline calories for women of equivalent size and age.
What Is TDEE?
Total Daily Energy Expenditure is your BMR multiplied by an activity factor that accounts for all movement throughout the day — from structured exercise to walking, fidgeting, and other non-exercise activity thermogenesis (NEAT). TDEE gives you the number of calories you need to consume to maintain your current weight. Eating below this number creates a calorie deficit (weight loss), while eating above it creates a surplus (weight gain).
Activity Multipliers Explained
The calculator uses five standard activity levels, each with a corresponding multiplier applied to your BMR:
- Sedentary (×1.2) — Desk job, little to no exercise. Most of the day is spent sitting.
- Lightly Active (×1.375) — Light exercise or walking 1–3 days per week.
- Moderately Active (×1.55) — Moderate exercise 3–5 days per week, such as jogging, cycling, or swimming at a steady pace.
- Very Active (×1.725) — Hard exercise or sports 6–7 days per week.
- Extra Active (×1.9) — Very intense training combined with a physically demanding job, or two-a-day training sessions.
Most people overestimate their activity level. If you are unsure, start with "Lightly Active" or "Moderately Active" and adjust based on real-world results over two to four weeks.
Calorie Targets for Weight Loss and Gain
A deficit of 500 calories per day below your TDEE corresponds to approximately one pound (0.45 kg) of fat loss per week, since one pound of body fat contains roughly 3,500 stored calories. Similarly, a surplus of 500 calories supports about one pound of weight gain per week. These are general guidelines — actual results depend on macronutrient composition, training stimulus, sleep quality, stress levels, and individual metabolism.
Macronutrient Breakdown
Once you know your calorie target, distributing those calories across protein, carbohydrates, and fat ensures balanced nutrition. This calculator provides three preset macro splits: a higher-protein ratio for cutting (to preserve muscle during a deficit), a balanced ratio for maintenance, and a higher-carb ratio for bulking (to fuel training and recovery). Protein is set at 4 calories per gram, carbohydrates at 4 calories per gram, and fat at 9 calories per gram.
Frequently Asked Questions
What is TDEE?
TDEE stands for Total Daily Energy Expenditure. It is the total number of calories your body burns in a 24-hour period, combining your BMR with calories burned through physical activity, digestion (the thermic effect of food), and non-exercise activity. Your TDEE represents the calorie intake needed to maintain your current body weight.
How accurate is the Mifflin-St Jeor formula?
Studies show the Mifflin-St Jeor equation predicts resting metabolic rate within 10% of measured values for most healthy adults. It is more accurate than the older Harris-Benedict equation and is the formula recommended by the American Dietetic Association for estimating calorie needs.
How many calories should I eat to lose weight?
A common and sustainable approach is to eat 500 calories below your TDEE each day, creating a weekly deficit of about 3,500 calories — equivalent to roughly one pound of fat. More aggressive deficits can lead to faster results but may also cause muscle loss, fatigue, and nutrient deficiencies. Consult a healthcare professional before starting any restrictive diet.
Should I eat back exercise calories?
If your activity level selection already accounts for your exercise routine, your TDEE estimate includes those calories. Eating additional "exercise calories" on top of your TDEE can lead to unintended surplus. It is generally better to choose an accurate activity level and eat consistently at your target rather than adjusting daily for individual workouts.
This calorie calculator is completely free, runs entirely in your browser, and stores nothing on a server. Bookmark this page to check your daily calorie needs anytime — quick, private, and instant.
Related reading: How to Calculate Your TDEE and Daily Calorie Needs