BMI Calculator
Calculate BMI with a full health report — BMR, TDEE, macros, ideal weight, body fat, and goal timeline.
How to use BMI Calculator
This BMI calculator delivers a complete health profile from a single form — BMI, body composition, daily calorie needs, macros, and a personalised goal timeline. Enter your height and weight to get your BMI instantly. The animated gauge shows exactly where you fall on the underweight-to-obese spectrum, and the result card shows your BMI Prime (how far you are from the healthy upper limit) and Ponderal Index alongside your standard BMI category. Add your age and gender to unlock two additional sections: Basal Metabolic Rate (the calories your body burns at complete rest, calculated using the clinically validated Mifflin-St Jeor equation) and an estimated body fat percentage with fat mass and lean mass values. Select your activity level to see your Total Daily Energy Expenditure across all five activity levels — from sedentary to very active — so you can see exactly how many calories your body burns at your lifestyle. Choose your goal — lose weight, maintain, or gain muscle — to get your target daily calorie intake and a full macro breakdown showing protein, fat, and carbohydrate grams per day. The goal timeline section is exclusive to this tool: it shows exactly how many weeks you need to reach a healthy BMI at both a 500 kcal per day deficit and a more sustainable 300 kcal per day deficit. Optionally enter your waist circumference to see your waist-to-height ratio, which research shows predicts cardiovascular risk more accurately than BMI alone — a ratio below 0.5 is the target regardless of gender. If you are of South or East Asian descent, enable the Asian BMI thresholds checkbox to apply the WHO Asia-Pacific guidelines, which use lower cut-off values that better reflect metabolic risk in Asian populations. All calculations run in your browser. Your last five results are saved locally for easy tracking over time.
Frequently Asked Questions
What is a healthy BMI range?
For adults, the World Health Organisation defines a healthy BMI as 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. For people of South or East Asian descent, the WHO Asia-Pacific guidelines use lower thresholds — overweight starts at 23.0 and obese at 27.5 — because health risks occur at lower BMI values in Asian populations.
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep your heart beating, lungs breathing, and organs functioning. TDEE (Total Daily Energy Expenditure) multiplies your BMR by an activity factor to estimate total calories burned per day including exercise and movement. Eating below your TDEE creates a calorie deficit that leads to weight loss; eating above it creates a surplus for weight gain.
How is body fat percentage calculated here?
This calculator uses the Deurenberg formula: Body Fat % = 1.20 × BMI + 0.23 × Age − 10.8 × Sex − 5.4 (where Sex = 1 for male, 0 for female). This is an epidemiological estimate derived from BMI, age, and gender — it is reasonably accurate for most adults but can overestimate body fat in highly muscular individuals. For a precise measurement, DEXA scanning or bioimpedance analysis is recommended.
What are the 4 ideal weight formulas and which should I use?
The four formulas — Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) — were originally developed for pharmaceutical drug dosing, not health prescriptions. Each uses slightly different multipliers and produces a slightly different result. The average across all four gives the most robust estimate. None account for muscle mass, frame size, or ethnicity, so treat the range as a rough reference alongside your healthy BMI weight range.
Why does the goal timeline show two different deficit levels?
A 500 kcal per day deficit produces roughly 0.5 kg of weight loss per week and gets you to your goal faster. A 300 kcal per day deficit is slower but significantly easier to sustain and causes less muscle loss during the process. Research shows that slower, moderate deficits result in better long-term weight maintenance. The timeline helps you set realistic expectations based on your preferred approach rather than giving a single optimistic number.