Health & Fitness
Track your body metrics and fitness goals with clinically-referenced formulas.
7 calculators
Health & Fitness calculators help you understand your body using the same formulas clinicians, trainers, and nutritionists rely on. Whether you're tracking progress toward a fitness goal, planning a pregnancy, or simply curious about your metabolism, this collection covers the core numbers people look up most: BMI, BMR, body fat percentage, ideal weight, calorie needs, water intake, and pregnancy due dates. Each calculator is built on a well-documented method — the Mifflin-St Jeor equation for metabolic rate, the U.S. Navy circumference method for body fat, and the Hamwi, Devine, Robinson, and Miller formulas for ideal weight — so you can see exactly how your result was reached rather than getting a black-box number. These tools are useful for anyone starting a weight-management plan, athletes monitoring training load, expecting parents estimating a due date, or people simply trying to stay adequately hydrated. They're designed to be fast and free, with no sign-up required. As with any health estimate, these results are educational starting points, not a diagnosis — always confirm important health decisions with a doctor or registered dietitian.
BMI Calculator
Calculate your Body Mass Index (BMI) using metric or imperial units and see which weight category you fall into.
Open calculatorBMR Calculator
Calculate your Basal Metabolic Rate (BMR) and daily calorie burn using the Mifflin-St Jeor equation.
Open calculatorBody Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method.
Open calculatorCalorie Needs Calculator
Calculate your daily calorie needs to maintain, lose, or gain weight.
Open calculatorIdeal Weight Calculator
Estimate your ideal body weight using the Hamwi, Devine, Robinson, and Miller formulas.
Open calculatorPregnancy Due Date Calculator
Estimate your pregnancy due date from your last menstrual period, conception date, or IVF transfer date.
Open calculatorWater Intake Calculator
Calculate your recommended daily water intake based on weight and exercise level.
Open calculatorFrequently asked questions
Are these health calculators medically accurate?
They use established, widely-referenced formulas (such as Mifflin-St Jeor for BMR and the U.S. Navy method for body fat), so results are accurate for the method used. However, they're estimates meant for general guidance, not a medical diagnosis — individual factors like muscle mass, medical conditions, and genetics can affect real-world results.
What's the difference between BMI and body fat percentage?
BMI compares your weight to your height and doesn't distinguish between muscle and fat, so it can be misleading for very muscular or very lean people. Body fat percentage estimates how much of your body mass is actually fat, giving a more direct picture of body composition.
How is BMR different from calorie needs?
BMR (Basal Metabolic Rate) is the energy your body burns at complete rest just to function. The Calorie Needs calculator takes that BMR and multiplies it by an activity factor to estimate how many calories you actually burn in a day, then adjusts further if your goal is to lose or gain weight.
Should I consult a doctor before using these results?
For general curiosity or casual tracking, these calculators are a fine starting point. If you're pregnant, managing a medical condition, or planning a significant change to your diet or exercise routine, talk to a doctor or registered dietitian before acting on any result.