Activity Level Formula: TDEE & Calorie Needs

This calculator works out your Total Daily Energy Expenditure (TDEE) — the number of calories you burn per day — using the Mifflin-St Jeor equation and an activity multiplier. You enter your age, sex, height, weight, and a typical activity level, and you get back your maintenance calories, plus your estimated calorie needs for weight loss and gain. The activity level formula is simply: TDEE = BMR × activity factor, where BMR is your basal metabolic rate and the activity factor ranges from 1.2 (sedentary) to 1.9 (very active).

Formula

The activity level formula is a two-step calculation:

• Step 1 – BMR (Mifflin-St Jeor):
  Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
  Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
• Step 2 – TDEE:
  TDEE = BMR × activity factor

Where:

• BMR (basal metabolic rate) – calories burned at complete rest, in kcal/day
• Activity factor – a multiplier that accounts for daily movement and exercise
• TDEE – total daily energy expenditure, in kcal/day

The standard activity factors are:

• Sedentary (little or no exercise): 1.2
• Lightly active (light exercise 1–3 days/week): 1.375
• Moderately active (moderate exercise 3–5 days/week): 1.55
• Very active (hard exercise 6–7 days/week): 1.725
• Extra active (very hard exercise, physical job, or training twice a day): 1.9

Worked Example

Using the default values: age 30, male, weight 70 kg, height 170 cm, moderately active (factor 1.55).

1. BMR = 10 × 70 + 6.25 × 170 − 5 × 30 + 5 = 700 + 1062.5 − 150 + 5 = 1617.5 kcal/day
2. TDEE = 1617.5 × 1.55 = 2507.125 ≈ 2507 kcal/day

So a 30-year-old man who is 170 cm, weighs 70 kg, and exercises moderately burns about 2507 calories per day. To lose weight, he would eat roughly 2007 kcal/day (a 500-kcal deficit); to gain, about 3007 kcal/day (a 500-kcal surplus).

How to Choose Your Activity Factor

Picking the right activity factor is the most common source of error. The descriptions are broad, so be honest about your typical week:

• Sedentary (1.2): Desk job, no exercise, mostly sitting or lying down.
• Lightly active (1.375): Light exercise 1–3 days per week, or a job that involves some standing/walking.
• Moderately active (1.55): Moderate exercise 3–5 days per week, or a job with regular walking.
• Very active (1.725): Hard exercise 6–7 days per week, or a physically demanding job.
• Extra active (1.9): Very hard daily exercise plus a physical job, or twice-a-day training.

If you are unsure, choose the lower option. Most people overestimate their activity level, which leads to an inflated calorie target and unexpected weight gain.

Common Mistakes and Misconceptions

• Using pounds and inches directly: The Mifflin-St Jeor equation requires kilograms and centimeters. To convert, divide pounds by 2.205 and inches by 0.3937.
• Confusing BMR with TDEE: BMR is only the resting component; your actual daily burn is higher unless you are bedridden.
• Double-counting exercise: The activity factor already includes exercise. If you add a separate workout tracker on top, you double count.
• Using a one-size-fits-all factor: The activity factor is a rough average. A 50-year-old and a 20-year-old with the same stats will have slightly different metabolic rates.
• Thinking the result is exact: This is an estimate. Individual variation is typically ±200–300 kcal/day.

Limits of the Formula

The Mifflin-St Jeor equation was developed from a sample of healthy adults and is most accurate for people with average body composition. It tends to overestimate calorie needs in very muscular individuals (because muscle burns more than fat) and underestimate in those with high body fat. It also does not account for medical conditions, medications, or hormonal differences. For most people, it is a good starting point, but you may need to adjust based on real-world results over 2–3 weeks.

Alternatives to the Activity Factor

If you want more precision, you can use a heart-rate monitor or a fitness tracker that estimates calories from your heart rate and movement. These devices still rely on an estimate of your BMR, but they replace the activity factor with actual measured activity. Another option is indirect calorimetry, a clinical test that measures the gases you inhale and exhale to directly determine your resting metabolic rate. It is the most accurate, but it is not available to most people outside a medical or sports science setting.

Safety and Healthy Use

Do not use this calculator as medical advice. A deficit of more than 500–1000 kcal/day can lead to muscle loss, nutrient deficiencies, and other health issues. Most health organizations recommend losing no more than 0.5–1 kg (1–2 lb) per week. If you are underweight, pregnant, nursing, or have a medical condition, consult a healthcare provider before changing your calorie intake. Never eat below your BMR for extended periods, as that can slow metabolism and cause health problems.

Frequently Asked Questions

What is the difference between BMR and TDEE?

BMR is the number of calories your body burns at complete rest (breathing, heartbeat, brain function). TDEE is BMR plus all the calories you burn through daily activities, exercise, and digestion. Your TDEE is always higher than your BMR unless you are immobile.

How accurate is the Mifflin-St Jeor equation?

It is considered the most accurate of the common predictive equations for healthy adults, with an error margin of roughly ±10%. That means a calculated TDEE of 2500 kcal could actually be anywhere from 2250 to 2750 kcal in practice.

Should I use the same activity factor every day?

No. If you have an active day, your actual burn is higher. The activity factor is an average for the week. If you are inconsistent, you can calculate a weekly average by multiplying each day’s factor by 7 and dividing by 7.

Can I use this formula for children or teenagers?

The Mifflin-St Jeor equation was developed for adults. For children and teenagers, growth and development alter energy needs significantly. Use a pediatric-specific formula or consult a pediatrician.

Why does the calculator ask for sex?

Men and women have different average body compositions, with men typically having more muscle mass, which raises BMR. The equation adds 5 for men and subtracts 161 for women to account for this difference.

What is the best way to adjust my calories if I am not losing weight?

If you have followed the calculated intake for 2–3 weeks and seen no change, reduce your intake by 100–200 kcal/day or increase your activity level. Conversely, if you are losing weight too fast, add 100–200 kcal/day. Always reassess after a few weeks.

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in age | Age | years | 30 | 15
in sex | Sex | Male=5, Female=-161 | 5 | 0
in weight | Weight | kg | 70 | 30
in height | Height | cm | 170 | 100
sel act | Activity Level | Sedentary=1.2, Light=1.375, Moderate=1.55, Active=1.725, Very Active=1.9 | 1.55 | 0
out tdee | Maintenance calories | kcal/day | (10 * weight + 6.25 * height - 5 * age + sex) * act | 0
out bmr | Basal metabolic rate | kcal/day | 10 * weight + 6.25 * height - 5 * age + sex | 0
out lose | Mild weight loss (−500 kcal) | kcal/day | (10 * weight + 6.25 * height - 5 * age + sex) * act - 500 | 0
out gain | Mild weight gain (+500 kcal) | kcal/day | (10 * weight + 6.25 * height - 5 * age + sex) * act + 500 | 0