Tool Stack

Health & Fitness Calculators

Free health tools for tracking fitness, nutrition, and wellness. For informational purposes only.

⚕️ These calculators are for general information only. Consult a healthcare professional for medical advice.

BMI Calculator

Calculate your Body Mass Index (BMI) and see which category you fall into.

BMR & TDEE Calculator

Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation.

Ideal Weight Calculator

Find your ideal body weight range based on height using the Robinson (1983) formula.

Body Fat Percentage Calculator

Estimate body fat % using the US Navy circumference method. All measurements in centimeters.

Daily Calorie Calculator

Find your recommended daily calorie intake based on your goal — maintain, lose, or gain weight.

Daily Water Intake Calculator

Find out how much water you should drink per day based on your weight and activity level.

Heart Rate Zone Calculator

Calculate your maximum heart rate and target heart rate zones for effective cardio training.

Pregnancy Due Date Calculator

Estimate your baby's due date from the first day of your last menstrual period (LMP). Based on the standard 280-day (40-week) gestation.

About Health & Fitness Calculators

Understanding your own body — how much energy it burns at rest, what weight range is healthy for your height, how many calories you need to fuel your activity level, and how much water you should be drinking every day — is the foundation of any effective fitness or nutrition strategy. Yet these calculations involve formulas that most people have never encountered outside a healthcare or sports science setting. Our free health and fitness calculators bring these formulas directly to you, requiring nothing more than a few personal measurements to produce clear, actionable numbers.

These tools draw on well-established, peer-reviewed methods: the Mifflin-St Jeor equation for BMR (considered the most accurate predictive formula for most adults), the US Navy circumference method for body fat estimation, and the standard 280-day gestation calculation for due date prediction. The results give you a meaningful starting point for understanding your body and planning your health goals. However, every individual is unique, and the numbers produced by any formula are estimates based on population averages. Always consult a qualified healthcare professional before making significant changes to your diet, exercise routine, or any medically relevant aspect of your lifestyle.

Available Tools

  • BMI Calculator — calculate your Body Mass Index from height and weight in metric or imperial units, with a category classification (underweight, healthy, overweight, obese).
  • BMR & TDEE Calculator — compute your Basal Metabolic Rate (calories burned at rest) and Total Daily Energy Expenditure (TDEE) adjusted for your activity level using the Mifflin-St Jeor equation.
  • Ideal Weight Calculator — find your ideal weight range for your height and biological sex using the Robinson (1983) formula.
  • Body Fat Percentage Calculator — estimate body fat percentage using the US Navy circumference method based on waist, neck, and hip measurements.
  • Daily Calorie Calculator — determine your recommended calorie intake for maintaining, losing, or gaining weight based on your personal stats and activity level.
  • Water Intake Calculator — find out how many liters or ounces of water you should drink per day based on body weight and activity level.
  • Heart Rate Zone Calculator — calculate your maximum heart rate and five training zones from warm-up to maximum effort for structured cardio workouts.
  • Pregnancy Due Date Calculator — estimate your baby's due date from the first day of your last menstrual period, based on the standard 280-day (40-week) gestation period.

Who Uses These Tools?

Fitness enthusiasts and gym-goers use the BMR and TDEE calculators to set calorie targets for cutting, bulking, or maintaining, and the heart rate zone calculator to ensure their cardio sessions hit the right intensity for fat burning, aerobic fitness, or peak performance. People on weight management journeys use the BMI, body fat, and ideal weight tools to track their progress objectively beyond just the number on the scale. Health coaches and personal trainers use these calculators with clients to set data-driven starting points for their programmes. Pregnant individuals and their partners use the due date calculator to plan ahead and understand their trimester timeline. General health-conscious users check their water intake recommendations to ensure adequate hydration, particularly when increasing exercise or living in hot climates.

Important Disclaimer

All tools on this page are intended for general informational and educational purposes only. They are not medical devices and do not provide medical diagnoses, treatment recommendations, or clinical advice. BMI, body fat percentage, and calorie estimates are population-based approximations that may not accurately reflect individual circumstances. If you have a medical condition, are pregnant, or are under medical supervision, consult your doctor or a registered healthcare professional before using these figures to guide health decisions.

Frequently Asked Questions

  • BMI (Body Mass Index) is a simple screening tool, not a diagnostic measure. It is calculated from height and weight alone, which means it cannot distinguish between fat mass and muscle mass. A highly muscular athlete may have a BMI classified as "overweight" even though their body fat percentage is excellent. Conversely, someone with a healthy BMI could still have a high proportion of dangerous visceral fat. BMI is best used as a rough population-level indicator alongside other measures such as waist circumference, body fat percentage, blood pressure, and cholesterol levels. Healthcare professionals rarely rely on BMI alone to assess an individual's health.

  • BMR (Basal Metabolic Rate) is the number of calories your body burns to maintain basic physiological functions — breathing, circulation, cell repair, temperature regulation — while at complete rest. It represents the minimum energy your body needs to stay alive and typically accounts for 60–75% of total daily calorie expenditure. Knowing your BMR is the foundation of any evidence-based nutrition plan: if you consistently eat fewer calories than your total daily energy expenditure (TDEE = BMR multiplied by an activity factor), you will lose weight; if you eat more, you will gain. The Mifflin-St Jeor equation used by our calculator is currently considered the most accurate formula for estimating BMR in most non-athlete adults.

  • General guidelines suggest approximately 35 ml of water per kilogram of body weight per day as a baseline for sedentary adults. Our water intake calculator adjusts this upward for moderate and active lifestyles, as exercise, heat, and perspiration significantly increase fluid requirements. A common rule of thumb is eight 8-ounce glasses (about 2 liters) per day, but this figure does not account for body size or activity and should be treated as a rough minimum. Note that fluid intake includes water from food (fruits and vegetables contain significant water) as well as beverages. The best practical indicator of adequate hydration is urine color — pale yellow indicates good hydration; dark yellow suggests you need to drink more.

  • The calculator uses Naegele's rule, the standard clinical method: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). This method assumes a 28-day cycle and ovulation on day 14, which does not apply to every pregnancy. In practice, only about 5% of babies are born on their exact calculated due date; most arrive within two weeks either side. The due date is better understood as the midpoint of a normal delivery window. Your midwife or obstetrician will typically confirm or adjust the due date based on an early ultrasound measurement, which provides a more accurate gestational age estimate. Always rely on your healthcare provider's guidance over any online calculator.