Free BMI Calculator – Body Fat, Ideal Weight, TDEE & Macros
Our BMI calculator is the most comprehensive free health tool available — combining Body Mass Index, ideal weight, body fat percentage, BMR, TDEE, and macro calculator in a single, no-sign-up tool. Used by health-conscious individuals across the USA, UK, Canada, and Australia.
📊 BMI Calculator for Adults
Calculate your Body Mass Index using both metric (kg/cm) and imperial (lbs/ft) units. Results are categorized as Underweight, Normal, Overweight, or Obese using WHO and CDC clinical standards — the same benchmarks used by doctors across the US and UK.
👶 BMI Calculator for Children & Teens
Child BMI works differently from adults. Our BMI calculator for kids uses CDC age and gender percentile chartsfor ages 2-19. A percentile above 95th indicates obesity, while 5th-84th is considered a healthy weight range.
⚖️ Ideal Weight Calculator
We calculate your ideal weight using three medically recognized formulas: Devine, Robinson, and Miller. Plus a BMI-based healthy range of 18.5-24.9. Each formula gives a slightly different result — our tool shows all three so you can see the full picture.
🔥 TDEE & Calorie Calculator
Using the Mifflin-St Jeor equation — the most clinically accurate BMR formula — we calculate your Total Daily Energy Expenditure (TDEE)based on your age, gender, weight, height, and activity level. Then we show exact calorie targets for weight loss, maintenance, and muscle gain.
🥩 Macro Calculator (Keto, High Protein, Balanced)
Choose your diet style and get instant macronutrient targets in grams. Our keto macro calculator uses 70% fat, 25% protein, 5% carbs. High protein split uses 40% protein. Balanced follows the standard 30/40/30 protocol. All calculated from your personal TDEE.
🫀 Body Fat Percentage Estimator
Get a body fat percentage estimate based on your BMI, age, and gender using the Deurenberg formula. Results include your fat category (Essential, Athlete, Fitness, Acceptable, Obese) plus a health risk assessment for diabetes, heart disease, and joint problems.
📈 BMI Progress Tracker
Save your BMI readings over time with our local progress tracker. Your history is stored privately in your browser — no account needed, no data uploaded. Track your weight loss or muscle gain journey with a clean history table showing date, weight, and BMI.
🎯 Weight Loss Goal Planner
Enter your target weight and our calculator shows how long it will realistically take to reach your goal at a healthy rate of 0.5kg (1lb) per week. Includes your projected goal date — a simple, science-backed roadmap to your target.
BMI Chart for Adults – WHO Classification
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Low (but other risks) |
| 18.5 – 24.9 | Normal / Healthy | Minimal |
| 25.0 – 29.9 | Overweight | Moderate |
| 30.0 – 34.9 | Obese Class I | High |
| 35.0 – 39.9 | Obese Class II | Very High |
| 40.0 and above | Obese Class III | Extremely High |
*Source: World Health Organization (WHO) BMI Classification. For children and teens, age and gender-specific percentiles apply.
How to Calculate BMI – The Formula Explained
The BMI formula is straightforward:
- Metric: BMI = weight (kg) ÷ height² (m²) — Example: 70kg ÷ (1.75 × 1.75) = BMI of 22.9
- Imperial: BMI = (weight in lbs × 703) ÷ height² (inches²) — Example: (154lbs × 703) ÷ (69 × 69) = BMI of 22.7
Our calculator handles both formulas automatically with one-click unit switching between metric and imperial.
BMI Calculator – Frequently Asked Questions
What is a good BMI for a 50-year-old woman?
The standard healthy BMI range of 18.5-24.9 applies to all adults regardless of age. However, research suggests that older adults (65+) with a BMI of 25-27 may have better health outcomes than those in the lower normal range, as some extra weight provides reserves during illness. Always consult your physician for age-specific guidance.
Is BMI the same for men and women?
Yes, the BMI formula and healthy range (18.5-24.9) is the same for both men and women. However, women naturally carry 5-8% more body fat than men at the same BMI, which is why our body fat estimator adjusts its calculation based on your gender.
How accurate is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population, with studies showing it predicts resting metabolic rate within 10% for most people. It outperforms the older Harris-Benedict equation and is the preferred formula used by dietitians and clinical nutritionists in the US and UK.
Can I use this BMI calculator for pregnancy?
Pre-pregnancy BMI is useful for understanding baseline health, but BMI during pregnancy is not a reliable health indicator as weight gain is expected and necessary. Always consult your OB-GYN or midwife for weight-related guidance during pregnancy.
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just keeping you alive. TDEE (Total Daily Energy Expenditure) adds your activity level on top of BMR to give your total daily calorie burn. TDEE is what you use to set your actual calorie intake goals.
⚕️ Medical Disclaimer: This BMI calculator is for informational and educational purposes only. Results do not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making decisions about your health, diet, or exercise program.