Free Health Calculators Online
3 health calculators. No signup, no data collected.
BMI Calculator
healthCalculate Body Mass Index with healthy weight range and target weight calculator.
Use toolCalorie Calculator
healthCalculate daily calorie needs (TDEE and BMR) with goal-based targets and macro breakdown.
Use toolWater Intake Calculator
healthCalculate daily water needs based on weight, activity level, and climate.
Use toolAbout These Health Calculators
Privatool's health calculators use clinically established formulas to give you meaningful wellness estimates in seconds. The BMI Calculator applies the standard WHO formula and supports both metric and imperial units, showing your classification and a contextual interpretation. The Calorie Calculator uses the Mifflin-St Jeor equation — the most accurate widely used method — to estimate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) based on age, sex, height, weight, and activity level. The Water Intake Calculator estimates daily hydration needs based on body weight and exercise. All inputs stay in your browser and are never sent to any server.
Why Use Browser-Based Health Calculators?
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Health data privacy
Weight, height, and age stay in your browser — never stored or shared.
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Science-based formulas
Uses WHO BMI standards and Mifflin-St Jeor TDEE equation.
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Metric and imperial
All tools support both kg/cm and lb/in inputs with automatic conversion.
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Instant results
Results update as you type — no button press or page reload needed.
Related Guides
Frequently Asked Questions
Are my health inputs stored or shared?
No. All health calculators run entirely in your browser. Your height, weight, age, and other personal inputs are never sent to a server, stored, or shared with any third party.
How is BMI calculated?
BMI is calculated as weight (kg) divided by height (m) squared: BMI = kg / m². The calculator supports both metric (kg/cm) and imperial (lb/in) inputs and converts automatically. Results are classified using the standard WHO categories: Underweight, Normal, Overweight, and Obese.
How accurate is the calorie calculator?
The calorie calculator uses the Mifflin-St Jeor equation, which is considered the most accurate formula for estimating Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). The result is an estimate — individual metabolism varies. Use it as a starting point and adjust based on real-world results.