Match the health calculator to its inputs
Start with the values you have. Age Calculator takes dates, BMI Calculator takes height and weight, and Body Fat Percentage Calculator takes body circumferences. Calorie Calculator estimates daily calorie needs, while Calories Burned Calculator estimates calories for one activity. Each page shows the inputs and assumptions beside the result.
What each calculator returns
- Age Calculator: Enter a date of birth and today or another target date. The result gives age in years, months, and days, plus total days, weeks, months, and the time until the next birthday. Leave the target date blank to use the browser's current date.
- BMI Calculator: Enter height and weight in metric or imperial units to calculate Body Mass Index (BMI). The result includes the standard weight category, intermediate values, and a copyable or downloadable result.
- Body Fat Percentage Calculator: Enter height, neck, and waist circumferences for the US Navy method. Women also enter hip circumference. The result includes a body-fat category and intermediate values in either metric or imperial units.
Separate daily estimates from activity estimates
- Calorie Calculator: Enter your measurements, age, sex, activity level, unit system, and goal. It estimates BMR, maintenance calories (TDEE), and a daily target for losing, maintaining, or gaining weight.
- Calories Burned Calculator: Enter body weight, an activity or custom MET value, and duration. Add distance when the selected activity supports it. The page shows the formula, MET value, intensity assumption, and a result range. It identifies the result as an estimate, not medical or nutritional advice.
Use Calorie Calculator for a daily target. Use Calories Burned Calculator for one session. Its displayed calculation is Calories = MET x weight (kg) x duration (hours); distance is used for walking, running/jogging, and cycling when applicable.
When to use BMI or body-fat percentage
BMI uses height and weight to calculate Body Mass Index and its standard category. Body Fat Percentage Calculator uses separate US Navy circumference formulas, so it requires height, neck, waist, and, for women, hip measurements. Choose BMI when height and weight are the measurements available. Choose the body-fat calculator when you can enter those circumferences.
Both results describe the measurements entered and the method shown on the page. The BMI Calculator and Body Fat Percentage Calculator use your numbers rather than live data, and neither result replaces a medical assessment.
Common starting points
- For a birthday or another date check, enter a birth date and target date in Age Calculator, then review the exact age and next-birthday timing.
- For height and weight, enter the measurements in BMI Calculator and review the category and intermediate values.
- For tape measurements, enter the required circumferences in Body Fat Percentage Calculator and review the category and displayed estimate.
- For food planning, use Calorie Calculator for a daily target. For a workout session, use Calories Burned Calculator with the activity and duration.
Choose by the values you can enter
Use Age Calculator for dates, BMI Calculator for height and weight, and Body Fat Percentage Calculator for the required circumferences. Choose Calorie Calculator for a daily estimate based on measurements and activity level. Choose Calories Burned Calculator for one activity, its duration, and any applicable distance. Their formulas and assumptions are shown with the selected result.
Frequently asked questions
Which health calculator should I use for body measurements?
Choose BMI Calculator when you have height and weight. Choose Body Fat Percentage Calculator when you also have the required neck and waist measurements, plus hip measurement for women. The calculators use different methods and report different estimates and categories.
What is the difference between daily calorie needs and calories burned?
Calorie Calculator estimates BMR, TDEE, and a goal-based daily target from measurements, age, sex, activity level, unit system, and goal. Calories Burned Calculator estimates one activity from body weight, activity or MET, duration, and applicable distance.
Can I calculate exact age from a date of birth?
Age Calculator calculates age from a date of birth to today or a target date in years, months, and days. It also shows total days, weeks, months, and time until the next birthday.
Do the health calculators show their assumptions?
Yes. The pages show the relevant formula, category, intermediate values, MET value, intensity assumption, or other calculation details for the selected result.