Free Health
Health calculators help you track and understand key metrics — BMI, calorie needs, body fat, macro targets, blood pressure, ovulation, pregnancy dates, and more. Results follow WHO and clinical guidelines. All calculations run in your browser and no personal health data is ever stored or transmitted.
18 tools available
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All Health (18)
Calculate Body Mass Index with metric or imperial units.
Open tool →Age CalculatorCalculate exact age in years, months, days with next birthday countdown.
Open tool →Calorie CalculatorCalculate BMR, TDEE, and daily calorie needs using the Mifflin-St Jeor equation.
Open tool →Ideal Weight CalculatorCalculate ideal body weight using Devine, Robinson, Miller, and Hamwi formulas.
Open tool →Sleep CalculatorFind ideal bedtime or wake-up time based on 90-minute sleep cycles.
Open tool →Pace CalculatorCalculate running pace, finish time, or distance. Shows km/mile splits for any race distance.
Open tool →BSA CalculatorCalculate Body Surface Area using Mosteller, Du Bois, Haycock, and Boyd formulas.
Open tool →Waist-to-Hip Ratio CalculatorCalculate WHR and WHtR with cardiovascular risk assessment per WHO guidelines.
Open tool →Water Intake CalculatorCalculate daily water intake based on body weight, activity level, and climate with a personalised hydration schedule.
Open tool →Body Fat CalculatorCalculate body fat percentage using the US Navy formula or BMI-based method. Shows lean mass, fat mass, and category.
Open tool →Pomodoro TimerOnline Pomodoro timer with customisable focus, short break, and long break durations. Tracks sessions and total focus time.
Open tool →Pregnancy Due Date CalculatorCalculate estimated due date from LMP, conception date, or IVF transfer. Shows weeks pregnant, trimester, and milestones.
Open tool →Macro CalculatorCalculate daily protein, carbs, and fat targets based on your BMR, TDEE, and fitness goal (cut, maintain, or bulk).
Open tool →Ovulation CalculatorCalculate ovulation date and fertile window from last period and cycle length. Shows cycle calendar and 3-cycle forecast.
Open tool →Blood Pressure CheckerCheck blood pressure readings against AHA guidelines. Classify as Normal, Elevated, or Hypertensive and log readings over time.
Open tool →Calories Burned CalculatorCalculate calories burned using MET values for 40+ activities. Supports metric and imperial with activity comparison.
Open tool →Heart Rate Zone CalculatorCalculate 5 heart rate training zones using the Karvonen formula or % of max HR. Includes fat burn, aerobic, and max effort zones.
Open tool →Love CalculatorFun love compatibility calculator. Enter two names and get a compatibility percentage score. Just for entertainment! 💕
Open tool →Frequently Asked Questions
- Are health calculators free?
- Yes. All health calculators are free with no sign-up and no usage limits.
- Are results medically accurate?
- Calculators use clinically validated formulas — Mifflin-St Jeor for BMR, Mosteller for BSA, WHO thresholds for BMI, AHA guidelines for blood pressure classification. Results are for informational purposes only; consult a healthcare professional for medical decisions.
- Is my health data stored?
- No. All calculations run in your browser. Stax does not store or transmit any personal health information.
- Are results in metric or imperial units?
- Most calculators support both metric (kg, cm) and imperial (lb, ft/in) units. You can switch between them within each tool.
- Which health calculators are available?
- Stax includes BMI, calorie, macro, body fat, BSA, ideal weight, waist-to-hip ratio, sleep cycle, running pace, heart rate zone, water intake, pregnancy due date, ovulation, blood pressure, calories-burned, and love compatibility calculators.