FitnessCalculator

Free Health & Fitness Calculators

Check your BMI, daily calorie needs, body fat percentage, ideal weight and water intake in seconds. Choose kilograms or pounds, centimetres or feet, on any tool. Nothing is stored and everything runs in your browser.

BMI Calculator

Body Mass Index. A quick screen for whether your weight sits in a healthy range for your height.
kg
cm
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Healthy weight range
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BMI calculator page: the formula, the chart and what the categories mean

Calorie / TDEE Calculator

Estimate the calories you burn daily and how much to eat to lose, maintain or gain weight.
kg
cm
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BMR (at rest)
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Mild weight loss
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Maintain
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Mild weight gain
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Calorie and TDEE calculator page: how BMR, activity and deficits fit together

Body Fat Calculator

Estimate body fat percentage using the U.S. Navy tape method.
cm
cm
in
cm
in
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Body fat calculator page: how to measure, and the percentage charts by age and sex

Ideal Weight Calculator

A healthy target-weight range for your height, based on established medical formulas.
cm
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Devine formula
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Robinson formula
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BMI-based range
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Ideal weight calculator page: where the formulas came from and what to use instead

Water Intake Calculator

How much water to drink per day based on your weight and exercise.
kg
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In cups (240 ml)
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In fluid ounces
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Water intake calculator page: daily targets by weight, and where the eight-glass rule came from

Each calculator on its own page

The same tool, with the formula written out, the reference charts and the questions people actually ask about it.

BMI Calculator Enter your height and weight to get your BMI, the category it lands in, and the… Calorie and TDEE Calculator Work out what you burn in a day, at rest and in total, then see the… Body Fat Percentage Calculator Estimate your body fat percentage from a tape measure using the US Navy circumference method. Men… Ideal Weight Calculator See what the Devine and Robinson formulas give for your height, shown next to the healthy… Water Intake Calculator Work out how much water to drink a day from your body weight and how long…

Read the guides

What each formula is doing, where it was derived, and the situations where it gives the wrong answer.

BMI scale showing the underweight, healthy, overweight and obese bands with cutoffs marked at 18.5, 25 and 30 What BMI Actually Measures, and Where It Falls Apart BMI is one division problem invented in the 1830s to describe populations, not people. Here is what it can tell you about… Bar chart comparing a 1,650 kcal resting BMR against a 2,558 kcal TDEE, with the 908 kcal activity gap bracketed BMR vs TDEE: Which Number Should You Actually Eat To? Your calculator gives you two numbers and they differ by 900 calories. One of them is a floor you should never eat… Chart of four calorie deficit sizes from 250 to 1,000 kcal per day and the weekly weight loss each one predicts How Big Should a Calorie Deficit Be? The 3500 calories per pound rule is wrong, but it is wrong in a useful way. What a sustainable deficit looks like… Column chart of the five TDEE activity multipliers, from 1.2 for a desk job to 1.9 for a physical job plus training Picking an Activity Multiplier Without Fooling Yourself The dropdown between Sedentary and Very Active swings your calorie target by 900 calories. Most people pick one band too high. Here… Diagram of a torso marking the three US Navy tape measurement sites at the neck, waist and hip The Navy Body Fat Method: How to Measure It and How Wrong It Can Be A tape measure and three circumferences give a body fat estimate accurate to about 3 percentage points, if you place the tape… Weight scale for a 180 cm man showing Devine at 75 kg, Robinson at 72.6 kg and the healthy BMI band from 59.9 to 81.0 kg Why Ideal Weight Formulas Disagree With Each Other Devine says 75 kg, Robinson says 72.6 kg, and the healthy BMI range says anywhere from 59.9 to 80.7 kg. All three… Stacked bar splitting daily fluid into 50 percent plain water, 30 percent other drinks and 20 percent food, beside the 3.7 L and 2.7 L targets How Much Water You Actually Need Per Day Eight glasses a day has no research behind it. The real numbers depend on your body weight, how much you sweat, and… Line chart of seven days of scale weight swinging 1.6 kg around a flat weekly trend line Why the Scale Jumps Two Kilos Overnight You ate well, trained hard, and woke up 1.8 kg heavier. Nothing went wrong. Here is what is actually moving, and how…
About these calculators

BMI is body weight in kilograms divided by height in metres squared. Daily calories use the Mifflin-St Jeor equation for resting metabolism, multiplied by an activity factor to give total daily energy expenditure (TDEE). Body fat uses the U.S. Navy circumference method. Ideal weight shows the Devine and Robinson formulas alongside the healthy-BMI range. Water intake is estimated from body weight plus an allowance for exercise. These are general estimates for healthy adults and do not replace medical advice.