Track your health metrics with accurate, science-based calculators. Make informed decisions about your wellness — completely free.
Understanding your body starts with knowing the numbers. Our health calculators use formulas validated by medical research to help you assess your weight, daily energy needs, and ideal targets. These tools are educational — always consult a healthcare professional for medical advice.
Estimate body fat percentage from tape measurements using the US Navy method, with fat mass, lean mass and reference ranges. Addresses the gap BMI leaves open.
NewCalculate your Body Mass Index and find out if you're in a healthy weight range for your height.
Most PopularCalculate your Basal Metabolic Rate and daily calorie needs based on your activity level.
FitnessFind your ideal body weight based on height, gender, and multiple scientific formulas.
HealthBMI tells you whether your weight is in a healthy range for your height. BMR tells you how many calories your body burns at rest. Ideal weight gives you a target backed by multiple medical formulas. Together, these three numbers create a clear picture of where you are and where you might want to be.
Our health tools are educational and based on widely accepted formulas like Mifflin-St Jeor, Devine, and Robinson. They don't account for muscle mass, body composition, or medical conditions. For personalized health planning, always consult a doctor, dietitian, or qualified healthcare professional.
BMI is accurate as a general indicator for most adults, but it doesn't distinguish between muscle and fat. Athletes with high muscle mass may have a high BMI but low body fat.
We use the Mifflin-St Jeor equation, which is considered the most accurate for the general population by current research.
BMI for children should be interpreted using age-and-sex-specific percentiles. Our adult calculators are designed for people 18 and older — please consult a pediatrician for children's health metrics.
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Back to HomepageHealth calculators translate published formulas into numbers you can read in seconds. That convenience is genuinely useful, and it carries a risk worth naming: a precise-looking number invites more confidence than the underlying method deserves.
Every tool in this category produces an estimate from a population-level formula. These formulas were developed by studying groups, and they describe groups well. Applied to one person, they can be substantially off, which is why each of our pages states the limitations alongside the result rather than after it.
| Calculator | What It Measures | Main Limitation |
|---|---|---|
| Body fat % | Proportion of weight that is fat | Tape technique drives most of the error |
| BMI | Weight relative to height | Cannot see muscle versus fat |
| BMR | Resting energy requirement | Estimates within about 10 percent |
| Calorie needs | Daily energy expenditure | Activity level is easily overstated |
| Ideal weight | Reference weight for height | Designed for drug dosing, not goals |
| Sleep cycles | Suggested sleep and wake times | Cycle length varies between people |
A calculator cannot examine you, review your medical history, or account for medications, conditions or context. Nothing on these pages is a diagnosis, and no result should delay speaking to a clinician about something that concerns you.
If you are trying to get a sense of your health, several measures carry more information than the outputs of a height-and-weight formula.
One measurement on one day tells you very little. Weight fluctuates by a kilogram or more within a day from fluid alone. If you are tracking anything, look at the direction over weeks rather than reacting to daily variation.
Weight-related numbers can be difficult for some people, and a calculator has no way of knowing that. If tracking these figures causes distress, or if you find yourself checking compulsively, stepping away from the numbers entirely is a reasonable and often healthier choice.
Research consistently finds that activity, diet quality, sleep and stress predict health outcomes better than weight alone. People at the same weight can have very different metabolic profiles. If weight is a genuine concern, a conversation with a doctor or registered dietitian who can see your whole situation will get you considerably further than any formula.