TDEE Calculator

TDEE Calculator: Mifflin-St Jeor Formula, Worked Examples & Complete Guide

Written by Magesh | Financial Tools & Calculation Specialist · Last updated July 31, 2026

In two sentences: A TDEE calculator estimates your Total Daily Energy Expenditure by first calculating your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, then multiplying by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active). This guide breaks down the exact formula, worked examples for men and women, and how to choose an honest activity multiplier instead of overestimating your daily movement.

What Is a TDEE Calculator?

A TDEE calculator estimates the total number of calories your body burns in a day, combining your resting metabolic needs with the energy cost of digestion and physical activity. TDEE — Total Daily Energy Expenditure — is the sum of your Basal Metabolic Rate (BMR), the thermic effect of food, non-exercise activity (NEAT), and exercise activity. If you eat at your TDEE, your weight stays roughly stable; eating below it drives weight loss, and eating above it drives weight gain.

The TDEE Formula: Mifflin-St Jeor Equation

For men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5. For women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161.

Men:   BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
Women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161

TDEE = BMR × Activity Multiplier

The only difference between the two formulas is the constant at the end: +5 for men, −161 for women — everything else is identical.

Activity Multipliers

Sedentary × 1.2, Lightly active × 1.375, Moderately active × 1.55, Active × 1.725, Very active × 1.9.

• Sedentary (1.2): desk job, little walking, no training.
• Lightly active (1.375): light exercise or sports 1–3 days per week.
• Moderately active (1.55): moderate exercise or sports 3–5 days per week.
• Active (1.725): hard exercise or sports 6–7 days per week.
• Very active (1.9): very hard training or a physically demanding job combined with regular exercise.

Worked Examples

Example 1: A lightly active woman

A 32-year-old woman, 168 cm, 68 kg, lightly active: BMR = (10 × 68) + (6.25 × 168) − (5 × 32) − 161 = 1,409 calories, and TDEE = 1,409 × 1.375 ≈ 1,937 calories/day.

Example 2: A moderately active man

A 40-year-old man, 180 cm, 85 kg, moderately active:

BMR = (10 × 85) + (6.25 × 180) − (5 × 40) + 5
BMR = 850 + 1,125 − 200 + 5 = 1,780 calories
TDEE = 1,780 × 1.55 ≈ 2,759 calories/day

Example 3: The impact of activity level on the same BMR

A 36-year-old woman with a BMR requiring roughly 1,241 calories at complete rest would need about 2,358 calories per day if extremely active, using a multiplier of 1.9 — nearly double her resting rate, showing how dramatically activity level changes total daily calorie needs even with an identical BMR.

Step-by-Step: How to Use a TDEE Calculator

1. Enter your weight in kilograms, height in centimeters, age, and sex.
2. The calculator computes your BMR using the Mifflin-St Jeor formula.
3. Select your activity level honestly — be careful not to assume your activity level is higher than reality; even someone training 6–7 days a week can still have a sedentary 1.2 multiplier if they also sit at a desk job all day, since the multiplier reflects overall daily movement, not just workout frequency.
4. Multiply your BMR by the selected activity factor to get your TDEE.
5. Treat the result as a starting point — track your actual intake and weight for 10–14 days, then adjust by ±100–200 calories based on what the scale actually shows.

Why Mifflin-St Jeor Over Other BMR Formulas

The Mifflin-St Jeor equation, published in 1990, is considered the most accurate option for modern populations, with an average margin of error around 5%, compared to 10–15% for older formulas. The older Harris-Benedict equation, created in 1919 and revised in 1984, tends to overestimate BMR by 5–15% in sedentary individuals — a meaningful gap that can lead to insufficient calorie deficits and weight loss plateaus if used for meal planning. Mifflin-St Jeor is generally favored over other formulas because it generates accurate results without requiring much math or knowledge of body fat percentage, which the more precise Katch-McArdle formula does require.

Limitations of the Mifflin-St Jeor Equation

The equation was developed using data from a specific population — primarily white Americans — and may be less accurate for individuals from different ethnic backgrounds or geographic regions. It also doesn’t directly account for variations in muscle mass and body composition, which can significantly impact metabolic rate — potentially underestimating BMR in individuals with high muscle mass and overestimating it in those with low muscle mass. For lean, highly muscular individuals, the Katch-McArdle formula, which factors in lean body mass, can produce a more accurate result, though it requires knowing your body fat percentage.

Using Your TDEE for Weight Goals

To lose weight, eat below your TDEE — a 500 calorie/day deficit yields roughly 1 pound of fat loss per week. Avoid going below 1,200 calories/day for women or 1,500 calories/day for men without medical supervision. To gain weight, eating consistently above TDEE (commonly 250–500 calories above) supports gradual weight gain, while eating at TDEE maintains your current weight.

Using a TDEE Calculator to Set Realistic Nutrition Goals

A TDEE calculator is most useful as the starting anchor for a nutrition plan, not a number to chase perfectly, since actual daily calorie burn fluctuates naturally from day to day.

A practical TDEE calculator workflow

1. Calculate your TDEE using an honest activity multiplier, not an aspirational one.
2. Set your calorie target relative to that TDEE number — typically a 300–500 calorie deficit for fat loss, or a 250–500 calorie surplus for muscle gain.
3. Track your actual body weight consistently for 2–3 weeks while eating at your calculated target.
4. Compare your real-world weight trend against what your TDEE calculator predicted — if the scale isn’t moving as expected, adjust your calorie target by 100–200 calories rather than assuming the formula is fundamentally wrong.
5. Recalculate your TDEE calculator result periodically as your weight changes, since a lower body weight generally means a lower BMR and therefore a lower TDEE going forward.

This iterative approach — using a TDEE calculator as a starting point and then calibrating against real results — consistently produces better outcomes than treating the initial formula output as a fixed, permanent number.

Frequently Asked Questions

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In summary, a TDEE calculator built on the Mifflin-St Jeor equation gives you a scientifically grounded starting point for daily calorie needs, and choosing your activity multiplier honestly — rather than optimistically — is what separates an accurate estimate from one that quietly sabotages a weight loss or muscle-gain goal.

About the author: Magesh is a Financial Tools & Calculation Specialist focused on building and fact-checking online calculators across health, fitness, and everyday measurement topics.

Note: This calculator and article are provided for general educational and informational purposes only and do not constitute medical or nutritional advice. Consult a doctor or registered dietitian before making significant changes to your diet, especially if you have an existing health condition.