Category 0220 Calculators

Health & Biophysics

Free health calculators to track your BMI, daily calorie needs, water intake, and sleep cycles. Fast, private, and simple to use.

Instant and free calculations100% private — runs in your browserStandard formulas

Body CompositionMetabolic RatesBiophysics & SleepFitness & Vitals

Health & Biophysics

Available Tools in Health & Biophysics

Select a model to begin real-time interactive computation.

20 Tools

Body Composition7 tools

BMI Calculator Body Fat Percentage Calculator (BMI)Ideal Body Weight Calculator (Devine Formula)Waist-to-Hip Ratio (WHR) Health Risk Calculator Waist-to-Height Ratio (WHtR) Calculator Pregnancy Weight Gain Calculator (IOM Guidelines)Child Growth Percentile Calculator (WHO / CDC Standards)

Chronology3 tools

Age Calculator Pregnancy Due Date Calculator Ovulation & Fertility Window Calculator

Metabolic Rates4 tools

Calorie Calculator Daily Water Intake Calculator Running Pace & Race Time Predictor Macronutrient (Protein, Carb, Fat) Split Calculator

Biophysics & Sleep2 tools

Sleep Cycle & Bedtime Calculator Next Period & Menstrual Cycle Predictor

Fitness & Vitals4 tools

One Rep Max (1RM) Strength Calculator Target Heart Rate Zone Calculator (Karvonen Formula)VO2 Max Estimator (Cooper 12-Minute Run Test)Blood Alcohol Content (BAC) Calculator (Widmark Formula)

Body Composition№ 02.01

BMI Calculator

Computes body mass index according to the WHO Quetelet equation with clinical percentile categories.

w (Mass in kg)h (Height in meters)

BMI = weight (kg) / [height (m)]²Launch

Chronology№ 02.02

Age Calculator

Calculates exact chronological elapsed time in years, months, weeks, days, and hours factoring leap years.

Birth DateTarget Date

ΔT = Date_Target − Date_BirthLaunch

Metabolic Rates№ 02.03

Calorie Calculator

Computes Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) via Mifflin-St Jeor.

w (kg)h (cm)a (years)s (sex)

BMR = 10w + 6.25h - 5a + sLaunch

Metabolic Rates№ 02.04

Daily Water Intake Calculator

Calculates optimal daily fluid hydration guidelines in Liters, Ounces, and glasses tailored to body weight, exercise, and climate.

Body WeightExercise DurationClimate Condition

Water (L) = Weight (kg) × 0.033 + (Exercise Min × 0.012)Launch

Biophysics & Sleep№ 02.05

Sleep Cycle & Bedtime Calculator

Calculates optimal bedtime and wake-up schedule using 90-minute ultradian REM sleep cycles to prevent sleep inertia and morning grogginess.

Target Time (Wake/Sleep)Sleep Cycles (4, 5, 6)Sleep Latency

Wake Time = Bedtime + (N × 90 min) + 14 min sleep latencyLaunch

Chronology№ 02.06

Pregnancy Due Date Calculator

Estimates expected date of delivery (EDD), current gestational week, and key milestone trimesters via Naegele's clinical rule.

First Day of Last Period (LMP)Average Cycle Length (28 days default)

EDD = LMP + 280 days (40 completed gestational weeks)Launch

Chronology№ 02.07

Ovulation & Fertility Window Calculator

Projects prospective ovulation day, peak 6-day fertile conception window, and upcoming menstrual cycle dates.

First Day of Last PeriodAverage Menstrual Cycle Length (21–35 days)

Ovulation = Next Period Start − 14 days ; Fertile Window = Days -5 to +1Launch

Body Composition№ 02.08

Body Fat Percentage Calculator (BMI)

Estimates total body fat percentage, fat mass, and lean mass using standardized circumference tape measurements | US Navy Method

Biological SexHeightNeck CircumferenceWaist CircumferenceHip Circumference (Women)

BF% (Men) = 495 / (1.0324 - 0.19077 log₁₀(W-N) + 0.15456 log₁₀(H)) - 450Launch

Body Composition№ 02.09

Ideal Body Weight Calculator (Devine Formula)

Calculates target healthy body weight for stature using the clinically established Devine, Robinson, Miller, and Hamwi equations.

Biological SexHeight (cm or ft/in)Formula Model (Devine / Robinson / Miller)

IBW (Men) = 50kg + 2.3 · (Height_in - 60) ; IBW (Women) = 45.5kg + 2.3 · (Height_in - 60)Launch

Metabolic Rates№ 02.10

Running Pace & Race Time Predictor

Computes running pace per kilometer or mile, split intervals, and predicts race finish times for 5K, 10K, half marathon, and marathon via Riegel's model.

Activity Time (hh:mm:ss)Distance (km / mi / standard race)Target Race Distance

Pace = Time / Distance ; Race Predictor: T₂ = T₁ · (D₂ / D₁)^1.06Launch

Fitness & Vitals№ 02.11

One Rep Max (1RM) Strength Calculator

Estimates the maximal lifting capacity (1RM) from submaximal repetitions using the verified Epley and Brzycki strength formulas.

Weight Lifted (kg or lbs)Repetitions Completed (1 - 12)

1RM_Epley = W · (1 + r/30) ; 1RM_Brzycki = W · [36 / (37 − r)]Launch

Metabolic Rates№ 02.12

Macronutrient (Protein, Carb, Fat) Split Calculator

Translates target daily caloric expenditure into exact grams of protein, carbohydrates, and dietary fats tailored to specific body composition goals.

Target Daily CaloriesGoal (Fat Loss, Muscle Gain, Endurance)Macro Ratio Preset

Protein(g) = (kcal · P%)/4 ; Carbs(g) = (kcal · C%)/4 ; Fat(g) = (kcal · F%)/9Launch

Body Composition№ 02.13

Waist-to-Hip Ratio (WHR) Health Risk Calculator

Evaluates visceral adiposity and cardiovascular disease risk based on the World Health Organization (WHO) waist-to-hip circumference criteria.

GenderWaist Circumference (cm or in)Hip Circumference (cm or in)

WHR = Waist Circumference / Hip CircumferenceLaunch

Body Composition№ 02.14

Waist-to-Height Ratio (WHtR) Calculator

Computes the waist-to-height ratio to assess early cardiometabolic mortality risk against the universal medical standard: keep your waist to less than half your height.

Waist Circumference (cm or in)Stature Height (cm or in)

WHtR = Waist Circumference / Stature HeightLaunch

Body Composition№ 02.15

Pregnancy Weight Gain Calculator (IOM Guidelines)

Tracks gestational maternal weight trajectories week-by-week against Institute of Medicine (IOM) clinical reference guidelines by pre-pregnancy BMI.

Pre-pregnancy WeightHeightCurrent Gestational WeekSingular vs Twin Gestation

Target Range = Baseline + (Trimester 1 fixed [0.5-2kg]) + (Weeks 14-40 × Weekly Rate by BMI category)Launch

Fitness & Vitals№ 02.16

Target Heart Rate Zone Calculator (Karvonen Formula)

Determines individualized aerobic, anaerobic, and fat-burn training heart rate zones using the physiological Karvonen Heart Rate Reserve (HRR) methodology.

Age (Years)Resting Heart Rate (BPM)Target Training Intensity Zone (%)

HR_target = [(HR_max − HR_rest) · %Intensity] + HR_rest ; HR_max = 220 − AgeLaunch

Fitness & Vitals№ 02.17

VO2 Max Estimator (Cooper 12-Minute Run Test)

Estimates maximal oxygen uptake (VO2 max in mL/kg/min) from the distance covered during Kenneth Cooper's standardized 12-minute aerobic field test.

Distance Covered in 12 Minutes (Meters or Miles)AgeGender

VO2_max (mL/kg/min) = (Distance in meters − 504.9) / 44.73Launch

Fitness & Vitals№ 02.18

Blood Alcohol Content (BAC) Calculator (Widmark Formula)

Estimates blood alcohol concentration percentage and hours to sobriety based on alcohol consumed, gender-specific volume of distribution, and metabolic decay.

Standard Drinks ConsumedBody WeightGenderHours Since First Drink

BAC(%) = [Alcohol (g) / (Weight (g) · r)] × 100 − (0.015 · Hours Elapsed) ; r_m=0.68, r_f=0.55Launch

Biophysics & Sleep№ 02.19

Next Period & Menstrual Cycle Predictor

Projects the calendar onset of your next menstrual period, PMS phase, and future cycle dates based on historic cycle interval averages.

First Day of Last PeriodAverage Cycle Length (21 - 45 Days)Period Duration

Next Period = Last Period Start Date + Average Cycle Length (Days)Launch

Body Composition№ 02.20

Child Growth Percentile Calculator (WHO / CDC Standards)

Maps infant and child height, weight, and BMI against World Health Organization (WHO) international growth reference distribution percentiles.

Child Age (Months or Years)Gender (Boy / Girl)Weight (kg)Height/Length (cm)

Percentile = Φ(Z) ; Z = [(Value / M)^L − 1] / (L · S) (Box-Cox LMS method)Launch

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Verified Formulas & 100% Private Calculations

All Health & Biophysics calculators run 100% privately in your local browser. No calculation data is ever stored or shared. We use standard formulas and verified algorithms so you can trust your results every time.