Free Health & Fitness Calculators
Understand your body with calculators based on standard, widely used formulas. Check your BMI, estimate how many calories you burn each day, measure body fat percentage and plan how much water to drink. Results are estimates for general information, not medical advice.
4 free tools
Which health calculator do I need?
Want a quick check of whether your weight suits your height? The BMI calculator gives your Body Mass Index, its category and the healthy weight range for your height, in metric or imperial units.
Planning to lose, maintain or gain weight? The calorie calculator estimates your BMR and total daily energy expenditure, then suggests daily calorie targets.
Curious how much of your weight is fat rather than muscle? The body fat calculator estimates body fat percentage from a few tape measurements.
Not sure you are drinking enough? The water intake calculator suggests a daily amount based on your weight, activity and climate.
The formulas behind our health calculators
Every calculator here uses a published, widely used method. BMI is weight in kilograms divided by height in meters squared, compared with the World Health Organization adult categories. Calorie estimates use the Mifflin-St Jeor equation, which research has found to be one of the more reliable ways to predict resting energy needs, multiplied by an activity factor.
Body fat is estimated with the U.S. Navy circumference method, which uses height plus neck and waist measurements (and hips for women). Water intake is based on body weight with adjustments for exercise and hot weather. Our guide what is BMI and what does your number mean explains the BMI categories and their limitations in detail.
All of these are estimates for healthy adults. They are useful for tracking trends and setting starting points, but they cannot account for every individual difference, and they are not a substitute for advice from a doctor or dietitian.
Tips for getting useful results
Measure consistently. Weigh yourself at the same time of day, ideally in the morning before eating, and take tape measurements in the same spots each time. Small day-to-day swings are normal, so look at the trend over several weeks.
Use more than one number. BMI does not separate muscle from fat, so pairing it with a body fat estimate and a waist measurement gives a fuller picture.
Enter measurements in the units you actually used. If your scale shows stones or pounds, the weight converter switches to kilograms in seconds.
The same goes for height and tape measurements: the length converter turns feet and inches into centimeters, so you can compare results from different calculators or charts.
Frequently asked questions
Are these health calculators a substitute for medical advice?
No. They provide general estimates based on standard formulas and are meant for information only. Speak to a doctor or registered dietitian before making major changes to your diet or exercise, especially if you have a medical condition or are pregnant.
Why is my BMI high when I am fit and muscular?
BMI only uses height and weight, so it cannot tell muscle from fat. Athletes and people who strength train are often classed as overweight. A body fat estimate gives better context in that case.
How accurate is the calorie estimate?
The Mifflin-St Jeor equation is usually within about 10% of measured resting energy use for most adults, but individuals vary. Treat the result as a starting point, track your weight for a few weeks and adjust your intake if it is not moving as expected.
Can children use these calculators?
They are designed for adults. Children and teenagers are still growing, so their BMI is assessed against age- and sex-specific growth charts, and their energy and fluid needs differ. A pediatrician can give appropriate guidance.