Free Online Health Calculators
BMI, body fat, BMR, heart rate zones, sleep cycles, hydration — estimate everyday health metrics in seconds. For reference only.
BMI Calculator
BMI with WHO and Asian classifications, plus your healthy weight range
Open tool →Body Fat Calculator
US Navy circumference method plus a BMI-based estimate, with classes
Open tool →BMR & TDEE
Mifflin-St Jeor BMR and TDEE with cut / maintain / bulk calorie targets
Open tool →Heart Rate Zones
Max HR via 220−age or Tanaka, split into five training zones
Open tool →Sleep Cycle Calculator
Plan wake-up or bedtime in 90-minute cycles; six cycles is ideal
Open tool →Water Intake
Daily water target from body weight (33 ml/kg) plus exercise time
Open tool →Blood Pressure Checker
Classify systolic/diastolic readings by both Chinese guidelines and AHA, with advice
Open tool →Why these health calculators?
Standard formulas
WHO and Asian BMI cut-offs, the US Navy circumference method, Mifflin-St Jeor, Tanaka and Karvonen — the same equations used in the published literature.
Private by design
Height, weight and circumferences are processed entirely in your browser; nothing ever leaves your device.
Actionable output
More than a number: classification tables, healthy weight ranges, training zones and calorie targets are shown alongside every result.