BMR & TDEE Calculator – Tutorial

What Is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate (BMR) is the minimum amount of energy your body needs to sustain only its vital functions while completely at rest (sleeping, fasting, motionless). This includes breathing, heartbeat, brain activity, cell renewal and maintaining body temperature.

BMR answers the question: "How many calories does my body burn per day even if I do nothing?"

The Mifflin–St Jeor Formula (Why This One?)

One of the most widely used and scientifically trusted formulas for BMR calculation today is the Mifflin–St Jeor equation. Developed in the 1990s, it has been shown to give more accurate results across different ages, sexes and body types compared to older formulas such as the Harris–Benedict equation.

BMR Formula

The Logic Behind the Formula

• Weight: As muscle and organ mass increase, energy needs increase.
• Height: A larger body surface area = more energy expenditure.
• Age: Metabolic rate generally decreases as age increases.
• Sex difference: An additional correction is applied due to average differences in muscle mass.

Step-by-Step BMR Calculation (Example)

Example: a 30-year-old male, 175 cm tall, weighing 75 kg:

1. 10 × 75 = 750
2. 6.25 × 175 = 1093.75
3. 5 × 30 = 150
4. BMR = 750 + 1093.75 − 150 + 5 = 1698.75 kcal/day

What Is TDEE? (Total Daily Energy Expenditure)

TDEE (Total Daily Energy Expenditure) represents the total energy you expend throughout the day. That is BMR + movement + daily life activities.

In real life nobody lies in bed all day. Walking, working, exercising — even standing — all burn calories. TDEE accounts for this difference.

TDEE Formula

What Do the Activity Multipliers Mean?

• 1.2 – Sedentary: Desk job, no exercise.
• 1.375 – Lightly active: Light exercise 1–3 days per week.
• 1.55 – Moderately active: Regular exercise 3–5 days per week.
• 1.725 – Very active: Intense training 6–7 days per week.
• 1.9 – Extremely active: Physical job + intense sport.

Example TDEE Calculation

For someone with BMR = 1699 kcal who is moderately active (1.55):

TDEE ≈ 1699 × 1.55 ≈ 2630 kcal/day

Where Are BMR and TDEE Used?

• Losing weight: eating fewer calories than TDEE
• Gaining weight: exceeding TDEE
• Maintaining weight: eating around TDEE
• Diet planning: setting a daily calorie target
• Sports programme: balancing training and nutrition

Important Warnings

BMR and TDEE are estimates. Actual metabolic rate varies from person to person.

• Individuals with higher muscle mass may have greater needs.
• Hormones, sleep, stress and genetics all have an effect.
• Metabolic adaptation can occur during prolonged dieting.

It is therefore best to treat this calculator as a "starting point." Subsequent adjustments should be made by observing changes in weight and energy levels.

Note: This content is for informational purposes and does not replace medical or nutritional treatment.