Accurate Body Health Calculators
Calculate your BMI, body fat, BMR, TDEE, and more with our trusted health tools. Based on CDC and WHO standards.
BMI Calculator
All Health Calculators
Choose from our comprehensive suite of body health calculators, all based on the latest CDC and WHO guidelines. TapDescription & FAQ on any card to learn more.
BMI Calculator
Calculate your Body Mass Index with age and gender-specific standards
Body Mass Index (BMI) is the CDC's standard screening tool for body weight classification. Enter your height and weight (US or metric units) to instantly see your BMI value, category (underweight, normal, overweight, obese), and what it means for your health. We follow the CDC adult BMI thresholds and support unit switching with one click.
What is a healthy BMI range?
A healthy BMI for adults is 18.5–24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese, per CDC guidelines.
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². With US units: BMI = (weight (lb) ÷ height (in)²) × 703.
Is BMI accurate for athletes?
BMI does not distinguish muscle from fat, so muscular athletes may read "overweight" despite low body fat. Use body-fat percentage for a clearer picture in that case.
Body Fat Percentage Calculator
Estimate body fat percentage using the US Navy circumference method
The US Navy body-fat formula uses simple circumference measurements (neck, waist, and hip for women) to estimate body fat percentage within about ±4% accuracy. Results are compared against ACE and CDC healthy ranges for men and women so you can see where you stand. Supports US and metric units.
How does the US Navy body fat formula work?
It uses waist, neck (and hip for women) circumference with height and sex. The formula correlates circumference to body density, then converts density to body fat percentage via the Siri equation.
How accurate is the Navy method?
When measurements are taken correctly it is accurate to about ±4%, making it one of the most reliable methods without clinical equipment like DXA.
What is a healthy body fat percentage?
For men, 10–20% is generally healthy; for women, 18–28%. Athletes run lower. Essential fat minimums are ~2–5% (men) and ~10–13% (women).
BMR Calculator
Calculate your Basal Metabolic Rate (Mifflin-St Jeor equation)
Your Basal Metabolic Rate (BMR) is the calories your body burns at complete rest to keep you alive. We use the Mifflin-St Jeor equation — the formula recommended by dietitians and the most accurate for modern populations. Enter age, sex, height, and weight to see how many calories you burn doing nothing but existing.
What is BMR?
BMR (Basal Metabolic Rate) is the energy your body needs at complete rest to power breathing, circulation, cell production, and brain activity. It accounts for 60–75% of daily calorie burn for most people.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is widely considered the most accurate for today's population and is the one used by most dietitians and clinical tools.
Why is my BMR lower as I age?
BMR drops about 2–5% per decade after 30, mainly due to age-related muscle loss (sarcopenia). Strength training helps preserve muscle and keep BMR higher.
TDEE Calculator
Compute Total Daily Energy Expenditure from BMR and activity level
TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor, giving the calories you burn in a typical day. It is the foundation of any weight-loss or muscle-gain plan: eat below TDEE to lose fat, above it to gain. Pick the activity level that matches your average week.
What is TDEE?
TDEE = BMR × activity multiplier. It estimates all calories burned in a day, including rest, digestion, and movement.
Which activity level should I pick?
Sedentary (desk job, little exercise) = ×1.2; Light (1–3 days/week) = ×1.375; Moderate (3–5 days) = ×1.55; Very active (6–7 days) = ×1.725; Extra active (physical job + training) = ×1.9.
How big a deficit should I use to lose weight?
A 15–20% deficit below TDEE (about 500 cal/day) supports roughly 1 lb of fat loss per week while sparing muscle, per CDC guidance.
Waist-to-Hip Ratio Calculator
Evaluate body shape and cardiovascular health risks (WHO standard)
Waist-to-hip ratio (WHR) measures where you carry fat. A higher ratio ("apple" shape) means more visceral fat around organs, which the WHO links to greater cardiovascular and metabolic risk. Enter your waist and hip measurements to get your WHR and WHO risk category.
What is a healthy waist-to-hip ratio?
The WHO recommends below 0.90 for men and below 0.85 for women. Above those values, cardiovascular and metabolic risk rises.
Where exactly do I measure waist and hip?
Waist: at the narrowest point, usually just above the navel. Hip: at the widest point around the buttocks. Measure with a tape kept level and snug, not tight.
Is WHR better than BMI?
WHR captures fat distribution, which BMI cannot. They complement each other — WHR is especially useful for "normal weight" people who carry excess abdominal fat.
Daily Water Intake Calculator
Estimate daily hydration needs from body weight and activity level
Proper hydration supports metabolism, temperature regulation, and cognition. This calculator estimates your daily water target from body weight (about 35 ml/kg) plus adjustments for exercise and hot climate, shown in liters, ounces, and cups.
How much water should I drink per day?
The CDC/NIH baseline is ~2.7 L for women and ~3.7 L for men from all beverages and food. This tool personalizes it to your weight and activity.
Does coffee count toward my water intake?
Yes. Moderate caffeine (3–4 cups/day) does not meaningfully dehydrate, so coffee and tea count toward your daily total.
Sleep Calculator
Find your ideal bedtime or wake time using 90-minute sleep cycles
Sleep happens in ~90-minute cycles. Waking at the end of a cycle helps you feel refreshed. Tell us when you need to wake up (or when you plan to sleep) and we'll suggest bedtimes or wake times for 4, 5, and 6 cycles, including a 15-minute fall-asleep allowance.
How much sleep do adults need?
The American Academy of Sleep Medicine recommends 7–9 hours for adults. This calculator targets the 7.5-hour (5-cycle) and 9-hour (6-cycle) marks.
What is a sleep cycle?
A full cycle lasts about 90 minutes across light, deep, and REM stages. Waking at the end of a cycle feels easier than mid-cycle.
Waist-to-Height Ratio Calculator
Assess cardiometabolic risk with the "keep waist < half height" rule
Waist-to-height ratio (WHtR) is a simple, powerful risk marker: a waist circumference less than half your height is linked to low cardiometabolic risk across ages, sexes, and ethnicities. This calculator gives your WHtR and a clear risk band.
What is the ideal waist-to-height ratio?
Aim for a ratio below 0.5 ("keep your waist circumference to less than half your height"). 0.43–0.52 is the healthy range for most adults.
Is waist-to-height ratio better than BMI?
Studies consistently find WHtR predicts cardiovascular risk at least as well as, and often better than, BMI — especially for "normal weight" people with central obesity.
FFMI Calculator
Measure Fat-Free Mass Index for athletes and lifters
FFMI (Fat-Free Mass Index) is like BMI but for muscle — it normalizes lean mass to height so you can compare muscularity regardless of stature. Enter your weight, height, and body fat percentage to get FFMI and normalized FFMI, plus a classification from below average to superior.
What is a good FFMI?
Average men score 18–20; 20–22 is above average; 22–23 is excellent; 25+ (normalized) is near the natural limit. Women average 14–18.
What is "normalized" FFMI?
Normalized FFMI scales your score to what it would be at 175 cm (5'9"), letting people of different heights be compared fairly.
Lean Body Mass Calculator
Calculate lean body mass using the Boer formula
Lean body mass (LBM) is everything in your body that isn't fat — muscle, bones, organs, water. It is needed for drug dosing, FFMI, and protein-target calculations. We use the Boer formula (recommended for adults), which estimates LBM from sex, weight, and height.
What is lean body mass?
LBM = total body weight minus fat mass. It includes muscle, bone, organs, and water. Knowing it helps set protein targets and some medication doses.
Which formula is used?
The Boer formula, which validation studies recommend for adults. It estimates LBM from sex, weight, and height without needing a separate body-fat measurement.
Ideal Body Weight Calculator
Estimate ideal body weight using Devine and Hamwi formulas
Ideal Body Weight (IBW) estimates a healthy weight for your height and sex, originally derived for drug dosing. We show the Devine, Hamwi, and Miller formulas and a healthy BMI-range weight (18.5–24.9) so you get a realistic target window rather than a single number.
What is ideal body weight?
IBW is an estimate of a healthy weight for a given height and sex, used historically for medication dosing and as a weight goal. We show multiple formulas plus the healthy-BMI weight range.
Which IBW formula should I use?
Devine is the most widely used. Because each formula gives a slightly different value, we display a range across Devine, Hamwi, and Miller plus the BMI-based healthy weight window.
Body Surface Area Calculator
Calculate BSA using the Mosteller formula (medical dosing)
Body Surface Area (BSA) is the total surface area of the human body, used for chemotherapy and medication dosing and cardiac-output indexing. The Mosteller formula is the simplest and most widely adopted: BSA = √(height × weight / 3600). Results are shown in m², ft², and in².
What is body surface area used for?
BSA is used for medication and chemotherapy dosing and to index cardiac output. It gives a dose proportional to body size more accurately than weight alone.
What is a normal BSA?
The average adult BSA is about 1.7 m² for women and 1.9 m² for men. Most adults fall between 1.6 and 2.0 m².
Weight Loss Calorie Deficit Calculator
Plan a safe calorie deficit and timeline to reach your goal weight
Set a realistic weight-loss plan based on your TDEE. Enter your current and target weight and how aggressively you want to cut (a 15–25% deficit is sustainable). We calculate your daily calorie target, expected weekly loss, and an estimated date to reach your goal, plus the safe-limit warning.
How big a calorie deficit is safe?
A 15–25% deficit below TDEE (about 300–700 cal/day) supports 0.5–1 lb of fat loss per week while preserving muscle. Deficits over 1,000 cal/day risk muscle loss and metabolic slowdown.
How long will it take to reach my goal?
Roughly 1 lb of fat ≈ 3,500 cal. We divide the total deficit needed by your daily deficit to estimate weeks to goal; results assume consistent adherence and adjust as your weight changes.
Weight Gain Calculator
Plan a lean calorie surplus and timeline to reach your goal weight
Build a healthy weight-gain (bulk) plan. Enter your current and target weight and desired surplus (10–20% above TDEE supports lean gain with minimal fat). We compute your daily calorie target, expected weekly gain, and estimated date to reach your goal.
How big a calorie surplus for lean muscle gain?
A 10–20% surplus above TDEE (about 250–500 cal/day) supports 0.25–0.5 lb of lean gain per week with minimal fat. Larger surpluses mostly add fat.
How fast can I gain weight healthily?
Beginners can gain 1–2 lb/month of muscle; experienced lifters less. Expect 0.5–1 lb/week total on a moderate surplus, with strength training required to direct calories toward muscle.
US vs Asian BMI Calculator
Compare your BMI under CDC and WHO Asian-population thresholds side by side
People of Asian descent tend to carry more body fat at lower BMI values, so the WHO Western Pacific Region sets lower cut-offs: overweight at 23, obesity at 27.5. This calculator shows your BMI classification under both the CDC (25/30) and Asian (23/27.5) standards at once.
Why are Asian BMI thresholds lower?
Asian populations accumulate visceral fat at lower BMI, raising cardiometabolic risk earlier. WHO Western Pacific Region and the International Diabetes Federation therefore set overweight at 23 and obesity at 27.5.
Which standard should I use?
Use the Asian cut-offs if you are of Asian descent; otherwise the CDC standard applies. This tool shows both so you can compare.
Healthy Weight Range Calculator
Find the weight range that matches a healthy BMI (18.5–24.9) for your height
Your healthy weight isn't one number — it's a range. This tool converts the CDC healthy BMI window (18.5–24.9) into a weight range for your exact height, shown in both pounds and kilograms, so you have a realistic target rather than a single figure.
What is a healthy weight range?
It's the weight range corresponding to a BMI of 18.5–24.9 for your height, per CDC standards. We compute it directly from your height.
Why a range and not one number?
Body composition, muscle mass, and frame size vary, so healthy weight spans about 15 kg. A range is more realistic than a single target.
Normal BMI Range by Age Calculator
See how the healthy BMI range shifts across children, adults, and seniors
The healthy BMI range is not one-size-fits-all. Children and teens use growth-chart percentiles, adults 20–64 use the standard 18.5–24.9, and adults 65+ may benefit from a slightly higher range (around 23–30). Enter your age to get age-appropriate guidance.
Does the healthy BMI range change with age?
For adults 20–64 the CDC range is 18.5–24.9. Research suggests adults 65+ may do better slightly higher (around 23–30). Children and teens use percentile-based assessment.
How is BMI assessed for children?
Ages 2–19 use CDC BMI-for-age growth-chart percentiles (85th = overweight, 95th = obese), not adult cut-offs.
Health Guides
Learn more about body health metrics with our comprehensive guides based on the latest research.
Healthy BMI Range
Understanding BMI categories and what they mean for your health
Body Fat Percentage Ranges
Ideal body fat levels for men and women by age
BMR vs TDEE
Learn the difference between basal and total energy expenditure
Ethnic Body Standards
How health standards differ across US ethnic groups
Grounded in Trusted Health Standards
Our calculators are based on standards from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), ensuring accuracy and reliability.
CDC Standards
WHO Guidelines
Health Information