What BMI is considered normal?

A BMI between 18.5 and 24.9 is considered normal weight by the WHO. Below 18.5 is underweight; 25–29.9 is overweight; 30 or above is obese.

How many calories do I need to lose weight?

To lose approximately 0.5 kg per week you need a deficit of 500 kcal/day compared to your TDEE (maintenance calories).

How much water should I drink per day?

The general recommendation is 33 ml per kg of body weight. For a 70 kg person, that is 2.3 litres per day, plus extra for exercise.

What is basal metabolic rate (BMR)?

BMR is the number of calories your body burns at rest to maintain vital functions. It is calculated using the Mifflin-St Jeor equation.

BMI Calculator

Last updated: 2026-05-09

The BMI Calculator is a free health calculator. Calculate your BMI and find out if your weight is healthy for your height. Get evidence-based estimates to improve your wellbeing.

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Common Sizes — Click to Fill

weight	height
60	165
70	170
80	175
90	180
100	185

What is BMI (Body Mass Index)?

BMI (Body Mass Index) is a numerical indicator that relates weight and height to estimate whether a person's body mass is appropriate for their height. It's the most widely used screening tool by the World Health Organization (WHO) to identify overweight and obesity in adults.

BMI formula

BMI = Weight (kg) ÷ Height² (m²)

Example: A person weighing 75 kg and 1.75 m tall has a BMI of 75 ÷ (1.75)² = 24.5

WHO BMI categories

Below 18.5: Underweight — possible malnutrition or health issues.
18.5 – 24.9: Normal weight — healthy range for most adults.
25.0 – 29.9: Overweight — increased risk of cardiovascular disease.
30.0 – 34.9: Obesity Class I — moderate risk.
35.0 – 39.9: Obesity Class II — high risk.
40+: Morbid obesity — very high risk of complications.

BMI limitations

Doesn't distinguish fat from muscle: A muscular athlete may show "overweight" BMI with very little body fat.
Doesn't measure fat distribution: Visceral (belly) fat is more dangerous than subcutaneous fat, but BMI doesn't differentiate.
Varies with age and sex: The same values carry different risks for men vs women, and for older people.

For a complete health assessment, consult a doctor and complement BMI with waist circumference and body fat percentage measurements.

Written and reviewed by the CalcToWork editorial team. Last updated: 2026-05-09.