Understanding your health numbers
BMI (Body Mass Index) is a widely used screening tool that divides your weight in kilograms by the square of your height in meters. A BMI under 18.5 is considered underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese. BMI does not directly measure body fat, so athletes with high muscle mass may score higher than expected.
Body fat percentage measured by the US Navy method uses circumference measurements to estimate fat vs. lean mass. It is one of the most accessible methods available without lab equipment. For men, essential fat is around 2 to 5 percent. For women, essential fat is around 10 to 13 percent. Fitness levels range from 14 to 24 percent for men and 21 to 31 percent for women.
TDEE (Total Daily Energy Expenditure) estimates how many calories your body burns in a day based on your basal metabolic rate and activity level. Eating below your TDEE creates a calorie deficit for weight loss. Eating above it supports weight gain. The calculator uses the Mifflin-St Jeor equation, which studies show is more accurate than older formulas like the Harris-Benedict equation.
Ideal weight calculated using the Hamwi method provides a reference range based on height and gender. It should be used as a general guideline rather than a strict target. Individual body composition, bone density, and muscle mass all affect what a healthy weight looks like for any specific person.
Water intake recommendations are based on body weight at 33 milliliters per kilogram, with additional fluid added for physical activity. Active individuals need more water to replace what is lost through sweat. Spreading water intake across the day is more effective than drinking large amounts at once.
Frequently asked questions
- Are these health calculators medically accurate?
- They use established formulas used by health professionals as screening tools. However, they are for general guidance only. For medical decisions, consult a qualified healthcare provider.
- Why does my BMI seem too high even though I exercise regularly?
- BMI does not distinguish between muscle and fat. Heavily muscled individuals often have a higher BMI despite having low body fat. In these cases, body fat percentage is a more useful metric.
- How often should I recalculate my TDEE?
- Recalculate whenever your weight changes significantly (5 kg or more), your activity level changes, or your age increases by a year. Your calorie needs shift as your body composition and lifestyle change.