Health Calculators
Quick, private health estimates — your body mass index and the calories you burn each day. Enter a few measurements and get a clear number with an honest explanation of what it means.
The two tools answer different questions. BMI describes where your current weight sits relative to your height; the calorie calculator estimates how much energy you burn in a day, which is what you adjust to change that weight. Used together, they give you a starting point and a daily target, both explained with the formula behind them.
How to choose the right calculator
You want to know whether your weight is in a healthy range
Use the BMI calculator. It needs only your height, weight and age, and it tells you which adult category your BMI falls into and the weight range that corresponds to a healthy BMI at your height.
You want a daily calorie target
Use the calorie calculator. It adds your sex and activity level to estimate your resting and daily calorie burn, then gives targets for maintaining, losing or gaining about a pound a week.
You are starting a weight goal
Run both. Check your BMI to see where you are and the healthy range to aim for, then use the calorie calculator to turn that goal into a daily number. Recheck both every few weeks rather than every day, since day-to-day weight changes are mostly water.
Guide to each calculator
Calorie / TDEE Calculator
Answers how many calories you burn in a typical day. Choose US or metric units and enter your age, sex, height, weight and activity level, from sedentary to very active. You get your basal metabolic rate from the Mifflin–St Jeor equation, your maintenance calories (TDEE), targets about 500 calories below and above maintenance for losing or gaining roughly a pound a week, and a daily protein target of 1.6 grams per kilogram of body weight. A warning appears when the weight-loss target falls below common minimums. Open the calorie calculator.
BMI Calculator
Answers which BMI category your height and weight fall into. Choose US or metric units and enter your height, weight and age. You get your BMI to one decimal place with its category (underweight, normal, overweight or obese), the healthy weight range for your height, how far you are from the obese line, and BMI Prime, which is your BMI divided by 25. The adult categories apply from age 20; for younger users, the page explains why pediatric percentiles are the right comparison. The method and its limits, such as not telling muscle from fat, are explained on the page. Open the BMI calculator.
What these numbers can and cannot tell you
Both calculators use population-level equations. BMI cannot distinguish muscle from fat, and calorie equations estimate an average person with your measurements, so your real needs can be higher or lower. Treat the results as a starting point: track your weight for a few weeks, adjust, and talk to a doctor or dietitian before major changes, especially if you are pregnant, under 20, or managing a medical condition.
Your data stays on your device
The calculations run in your browser. Height, weight, age and activity level are not sent to a server to produce the result, so you can try different values freely, for example to see how your calorie targets change with a different activity level.
About our health calculators
Our health calculators use the same published equations clinicians and dietitians start from: the standard BMI formula with CDC and WHO adult ranges, and the Mifflin–St Jeor equation for resting and daily calorie needs. Everything runs in your browser, so your height, weight and age never leave your device. The results are screening estimates, not a diagnosis — use them to understand where you stand and to have a better conversation with a healthcare professional.