Free Online Health Calculators

Select a tool below to get started. All calculations happen instantly in your browser — no data is ever stored or transmitted.

Results are estimates based on established medical formulas. They are for educational purposes only and do not replace professional medical advice.

BMI Calculator

Calculate your Body Mass Index using the World Health Organization (WHO) standard formula. BMI = weight (kg) ÷ height² (m²).

Weight (kg)

Height (cm)

Enter your weight and height, then click Calculate.

WHO BMI Classification

BMI	Category
Below 18.5	Underweight
18.5 – 24.9	Normal Weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obese Class I
35.0 – 39.9	Obese Class II
40.0+	Obese Class III

Daily Calorie Calculator

Estimate your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation — the gold standard recommended by most registered dietitians.

Age (years)

Biological Sex

Weight (kg)

Height (cm)

Activity Level

Your Goal

Fill in your details and click Calculate to see your daily calorie target.

Ideal Weight Calculator

Calculate your ideal body weight range using four established clinical formulas: Hamwi, Devine, Robinson, and Miller.

Biological Sex

Height (ft)

Height (in)

Select your sex and enter your height, then click Calculate.

Blood Pressure Category Checker

Identify your blood pressure category using the American Heart Association (AHA) 2017 guidelines. Enter your most recent reading below.

Systolic Pressure (mmHg) — the top number

Diastolic Pressure (mmHg) — the bottom number

Enter your systolic and diastolic readings, then click Check.

AHA Blood Pressure Categories

Category	Systolic	Diastolic
Normal	< 120	< 80
Elevated	120–129	< 80
High — Stage 1	130–139	80–89
High — Stage 2	≥ 140	≥ 90
Hypertensive Crisis	> 180	> 120

Body Fat Percentage Calculator

Estimate your body fat percentage using the U.S. Navy circumference method — requires only a tape measure.

Biological Sex

Height (cm)

Waist circumference (cm) — measure at navel level

Neck circumference (cm) — measure just below the larynx

Hip circumference (cm) — widest point (women only)

Enter your measurements and click Calculate.

Heart Rate Zone Calculator

Find your 5 personalised training zones using the Karvonen formula. Add your resting heart rate for maximum precision.

Age (years)

Resting Heart Rate (bpm) — optional, for better accuracy

Enter your age and click Calculate to see your training zones.

Daily Water Intake Calculator

Calculate how much water you should drink each day based on your body weight, activity level, and climate.

Body Weight (kg)

Activity Level

Climate / Environment

Enter your weight and activity level, then click Calculate.

Pregnancy Due Date Calculator

Estimate your baby's due date using Naegele's Rule based on your last menstrual period (LMP) or a known conception date.

Calculate from:

First day of your Last Menstrual Period

Conception Date

Average cycle length (days)

Select your method and enter the date, then click Calculate.

This is an estimate only. Your healthcare provider will confirm your official due date through ultrasound. Most babies arrive within 2 weeks before or after the estimated date.