Health Calculators
Baby Height Percentile Calculator
Estimate your baby's length percentile from 0 to 24 months against WHO Child Growth Standards reference medians, broken down by age in months and by sex.
Baby Weight Calculator
Estimate fetal weight from ultrasound measurements using the Hadlock formula, based on head circumference, biparietal diameter, abdomen, and femur length.
Blood Alcohol Content Calculator
Estimate Blood Alcohol Content using the Widmark formula from body weight, sex, number of standard drinks consumed, and the hours elapsed since drinking began.
Blood Pressure Calculator
Classify blood pressure by AHA category, or calculate Mean Arterial Pressure and pulse pressure directly from systolic and diastolic readings entered.
Blood Sugar Converter
Convert blood glucose values between mg/dL and mmol/L using the standard conversion factor, with a reference table of common blood glucose values shown.
BMI Calculator
Calculate Body Mass Index from height and weight in metric or imperial units, with WHO adult BMI categories from underweight through obese for reference.
BMR Calculator
Find your Basal Metabolic Rate, the calories your body burns at rest, using the Mifflin-St Jeor equation from your age, sex, weight, and height measurements.
Body Fat Calculator
Estimate body fat percentage using the US Navy circumference method, based on neck, waist, and hip measurements plus height, for both men and women alike.
Body Water Calculator
Estimate total body water in liters and as a percentage of body weight using the Watson formula, based on your age, sex, height, and current body weight.
Caloric Deficit Calculator
Calculate your daily caloric deficit or surplus from TDEE and current calorie intake, with estimated weekly weight change shown in pounds and kilograms too.
Calorie Calculator
Estimate daily calorie needs using the Mifflin-St Jeor equation, adjusted for age, sex, weight, height, and activity level from sedentary to extra active.
Carbs Calculator
Calculate a daily carbohydrate target in grams from total calories and a target carb percentage, with the standard AMDR range shown for comparison too.
Cholesterol Ratio Calculator
Calculate your total cholesterol to HDL ratio and risk category, with optional LDL estimation from your triglycerides via the Friedewald formula shown.
Drip Rate Calculator
Calculate IV drip rate in drops per minute from infusion volume, elapsed time, and the administration set's drop factor in drops per milliliter of fluid.
Fat Calculator
Calculate a daily dietary fat target in grams from total calories and a target fat percentage, with the standard AMDR range shown for easy comparison.
Fertility Window Calculator
Estimate your fertile window and ovulation day from your last period date, your average cycle length, and your luteal phase length entered directly by you.
Fiber Calculator
Find your recommended daily fiber intake in grams by age and gender using Institute of Medicine reference tables, plus an alternative calorie-based estimate.
Fluid Balance Calculator
Calculate net fluid balance by comparing total intake from oral, IV, and other sources against total output from urine, stool, and other fluid losses each day.
Ideal Weight Calculator
Calculate ideal body weight ranges by height and gender using the Devine, Robinson, Miller, and Hamwi reference formulas shown side by side for comparison.
Iron Calculator
Find your recommended daily iron intake in milligrams by age, gender, and status, covering infancy through adulthood, pregnancy, and lactation stages.
IV Infusion Calculator
Calculate IV flow rate in mL per hour and drip rate in drops per minute together from total infusion volume, elapsed time, and the chosen set's drop factor.
Lean Body Mass Calculator
Estimate lean body mass and fat mass using the Boer formula from weight, height, and sex, separating fat-free tissue from total body weight precisely.
Life Expectancy Calculator
Estimate life expectancy from national baseline averages adjusted for smoking status, exercise level, BMI category, and alcohol consumption habits shown.
Likelihood Ratio Calculator
Calculate positive and negative likelihood ratios from a diagnostic test's sensitivity and specificity, with a general clinical interpretation guide included.
Macro Calculator
Calculate daily protein, carbohydrate, and fat targets in grams from your total calories and a chosen macro split, with standard AMDR ranges for reference.
Period Calculator
Track menstrual cycle timing and predict your next period date and fertile window start date from your last period start date and average cycle length.
Potassium Calculator
Find your recommended daily potassium intake in milligrams by age, gender, and status, based on current NASEM Adequate Intake reference values used today.
PPV/NPV Calculator
Calculate positive and negative predictive value from a diagnostic test's true positive, false positive, true negative, and false negative result counts.
Protein Calculator
Calculate a daily protein intake range in grams from body weight and your activity category, spanning sedentary minimums up to strength-training targets.
Recipe Nutritional Calculator
Calculate per-serving calories, protein, carbs, and fat from a recipe's total nutrition values and its number of servings, cross-checked automatically.
Sensitivity/Specificity Calculator
Calculate diagnostic test sensitivity and specificity from true positive, false negative, true negative, and false positive case counts entered manually.
Sleep Calculator
Find bedtimes or wake times aligned to complete 90-minute sleep cycles, working forward from a chosen bedtime or backward from a fixed wake-up time each day.
Smoking Cost Calculator
Calculate the daily, weekly, monthly, yearly, and lifetime cost of smoking from cigarettes smoked per day, cigarettes per pack, and the price paid per pack.
Sodium Calculator
Find your recommended daily sodium upper limit in milligrams by age, converted into an equivalent weight of ordinary table salt measured in grams too.
TDEE Calculator
Calculate Total Daily Energy Expenditure from Mifflin-St Jeor BMR and an activity multiplier, showing exactly how much activity level shifts calorie needs.
Vitamin D Calculator
Find your recommended daily Vitamin D intake in IU and micrograms by age, with separate adjustments shown for pregnancy and lactation status as needed.
Waist to Hip Ratio Calculator
Calculate waist-to-hip ratio from waist and hip measurements, classified against WHO risk thresholds for men and women to flag fat distribution risk factors.
Water Intake Calculator
Calculate a daily water intake target in liters, ounces, and cups from body weight plus exercise minutes, using standard hydration baseline figures used widely.
The Numbers Behind Everyday Health Decisions
A handful of health metrics get checked constantly, at home and in a doctor's office alike — BMI, BMR, blood pressure, body fat percentage — and understanding what they actually measure (and where they fall short) matters as much as the number itself. Thirty-eight calculators here cover body composition, nutrition, and general health tracking.
Popular Health Calculators
Highlights across body composition, nutrition, and vitals:
- BMI Calculator — calculates body mass index from height and weight, a widely used but limited screening measure.
- BMR Calculator — estimates calories burned at rest, the baseline for any calorie budget.
- TDEE Calculator — combines BMR with activity level to estimate total daily energy needs.
- Body Fat Calculator — estimates body fat percentage using measurement-based methods like the U.S. Navy formula.
- Blood Pressure Calculator — classifies a blood pressure reading against standard clinical categories.
Why BMI Is a Screening Tool, Not a Diagnosis
BMI was designed as a population-level screening statistic, not an individual diagnostic measure — it uses only height and weight, so it can't distinguish muscle mass from fat mass, which is exactly why a muscular athlete can register as "overweight" on the BMI scale despite low body fat. Body fat percentage calculators exist to address that gap more directly, using actual circumference measurements or other methods to estimate fat mass rather than relying on a simple height-weight ratio, though even those methods carry their own margins of error compared to clinical methods like DEXA scans.
Frequently Asked Questions
Is TDEE more useful than BMR for weight management?
For setting a calorie target, yes — BMR only reflects calories burned at complete rest, while TDEE adds activity level, making it the more relevant number for planning an actual daily calorie intake.
Why do blood pressure categories keep getting updated?
Clinical guidelines are periodically revised as new research on cardiovascular risk emerges, which is why "normal" blood pressure thresholds have shifted over time and can differ slightly between health organizations.
Explore More
Tracking workouts and performance too? See the Fitness Calculators, or dig into nutrition specifics in the Nutrition Calculators.