BMI & ideal weight calculator
Compute your BMI in 10 seconds and find your target ideal weight through 3 medical formulas (Lorentz, Creff, Devine). Bonus: body age and clear target.
Indicative tool. Calculations do not replace medical advice.
Your result
Est. body age
Based on BMI + ideal weight gap (approximation)
Target ideal weight
Smoothed average of the 3 formulas
Go deeper
BMI: a WHO-validated health benchmark
The Body Mass Index (BMI) is the World Health Organization's reference indicator to assess adult body composition. Its formula is simple: weight (kg) divided by height squared (m²). For 70 kg and 1.75 m, BMI = 70 / (1.75 × 1.75) = 22.9.
The 4 BMI zones to know
Underweight
Too low: risk of deficiencies, fatigue, weakened immunity.
Healthy weight
Considered the most favorable zone for long-term health.
Overweight
Slight excess. Watch your diet and physical activity.
Obesity
Increased cardiovascular risk. Medical advice is recommended.
3 formulas for a realistic ideal weight
BMI alone has limits: it doesn't separate muscle from fat. Our tool cross-references three recognized medical formulas and averages them for a realistic target.
- Lorentz: classic formula, factors gender and height. The most widely taught reference.
- Creff: adds age to correct for the metabolism slowing with the years.
- Devine: US medical standard, used in pharmacology for dosing.
Body age: a quick reading
Our estimated body age indicator compares your real BMI to the ideal zone (18.5–25):
- Normal BMI: "youth" bonus — your body works well.
- Overweight: slight metabolic aging beyond 25.
- Underweight: penalty due to nutritional deficits.
Indicative approximation — does not replace a medical analysis (bioimpedance, blood test).
When BMI lies
The official BMI doesn't separate muscle from fat. A muscular athlete may be classified as "overweight" or "obese" without any real risk. Conversely, a sedentary person of "normal" BMI may carry too much body fat (skinny fat). BMI stays a statistical benchmark: for a finer reading, combine it with waist measurement, a bioimpedance scale or a professional opinion.
FAQ
Is BMI reliable if I am very athletic?
Not really. Muscle is heavier than fat at equal volume. If you lift or do intensive sports, your BMI may land in the "Overweight" zone with no actual health risk. Complement with waist measurement or a bioimpedance scale.
Does BMI apply to children?
No. This tool is designed for adults aged 18 to 65. For children and teens, specific growth charts are used since their body is still developing.
Is there a different BMI for men and women?
Officially no: WHO applies the same thresholds. But physiology differs (men have more muscle and bone mass). That's precisely why the Lorentz and Devine ideal-weight formulas adjust by gender to give you a target that respects your body type.
Why 3 formulas for the ideal weight?
No formula is perfect: Lorentz ignores age, Creff is more subjective, Devine comes from a US drug-dosing context. Cross-referencing the three and showing the average smooths the gaps for a realistic target rather than an arbitrary number.
Is my data sent to a server?
No. All calculations run in your browser. No data (weight, height, age) is sent or stored server-side.
How accurate is the displayed body age?
It's an indicative approximation based on the gap between your BMI and the normal zone (18.5–25). For a real biological-age measurement, only a full medical assessment (bioimpedance, blood test, biomarkers) is reliable.
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Ideal weight
Calculate your target weight in 10 seconds. The simulator combines the 3 reference medical formulas — Lorentz, Creff and Devine — and shows the average for a realistic health goal.