ToolSpotAI

Free BMR Calculator

Calculate your Basal Metabolic Rate using Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle. See TDEE by activity level. This tool runs in your browser—no account required.

Health

Your Basal Metabolic Rate (BMR)

1,699

calories per day

Using Mifflin-St Jeor formula

Mifflin-St Jeor

1699 cal

Most accurate

Harris-Benedict

1763 cal

Katch-McArdle

N/A

Total Daily Energy Expenditure (TDEE)

Sedentary

Little or no exercise, desk job

2,039
Lightly Active

Light exercise 1–3 days/week

2,336
Moderately Active

Moderate exercise 3–5 days/week

2,633
Very Active

Hard exercise 6–7 days/week

2,930
Super Active

Intense exercise + physical job

3,228

Weight Loss

2,133

−500 cal/day

Maintain

2,633

No change

Weight Gain

3,133

+500 cal/day

About Mifflin-St Jeor

The Mifflin-St Jeor equation (1990) is considered the most accurate for estimating BMR in healthy adults. It uses weight, height, age, and sex. Male: (10 × weight) + (6.25 × height) − (5 × age) + 5. Female: same but − 161.

How to Use This BMR Calculator

  1. Enter your age, gender, height, weight, and optionally body fat percentage.
  2. Select a formula (Mifflin-St Jeor is recommended).
  3. The calculator computes your BMR and then multiplies it by activity factors to show TDEE at each level.
  4. Goal calories are calculated as TDEE ± 500 calories for moderate weight change.

What is BMR Calculator?

A BMR calculator estimates your Basal Metabolic Rate — the minimum calories your body needs to function at rest. Understanding your BMR is the foundation for any diet, fitness, or weight management plan because it tells you how many calories you burn just by existing. Our calculator supports three scientifically validated formulas: Mifflin-St Jeor (most accurate for general use), Harris-Benedict (classic formula), and Katch-McArdle (body fat-based). It also shows your TDEE at five activity levels and goal calories for weight loss, maintenance, or gain.

Formula

Mifflin-St Jeor:
Male: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Female: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

Harris-Benedict:
Male: 88.362 + (13.397 × weight) + (4.799 × height) − (5.677 × age)
Female: 447.593 + (9.247 × weight) + (3.098 × height) − (4.330 × age)

Katch-McArdle: 370 + (21.6 × lean body mass kg)

Formula Explained

All formulas estimate resting energy expenditure using body metrics. Mifflin-St Jeor (1990) is the most recent and accurate. Harris-Benedict (1919, revised 1984) tends to overestimate by 5–15%. Katch-McArdle ignores sex and age, using only lean mass — more accurate for athletic individuals who know their body fat percentage.

Example

Male, 30 years, 75 kg, 175 cm Mifflin-St Jeor: (10×75) + (6.25×175) − (5×30) + 5 = 1,693 cal/day TDEE: Sedentary: 1,693 × 1.2 = 2,032 Moderately Active: 1,693 × 1.55 = 2,624 Very Active: 1,693 × 1.725 = 2,920 Goal calories (moderate activity): Weight loss: 2,124 cal/day Maintain: 2,624 cal/day Weight gain: 3,124 cal/day

Tips & Best Practices

  • ✓Use Mifflin-St Jeor as your default — it is the most validated formula.
  • ✓If you know your body fat %, try Katch-McArdle for a more personalized result.
  • ✓Never eat below your BMR for extended periods — it can slow your metabolism.
  • ✓Recalculate every 5–10 lbs of weight change as your BMR shifts.
  • ✓Activity level is the most subjective part — be honest about your exercise frequency.

Common Use Cases

  • •Determining daily calorie needs for weight loss or gain
  • •Setting up a macro-based nutrition plan
  • •Understanding how exercise affects total energy expenditure
  • •Comparing BMR formulas for personalized accuracy
  • •Planning diet strategies for fitness and body composition goals

Frequently Asked Questions

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell production, and brain function. It represents about 60–75% of your total daily energy expenditure. Think of it as the calories you would burn if you stayed in bed all day.

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