Work out your BMI, simulate your weight loss
Your body mass index on the scale of the World Health Organization, then an estimate of the time it would take you to reach your goal.
BMI calculator
This tool gives a landmark for adults. It does not replace the advice of a health professional.
How is BMI worked out?
Body mass index (BMI) divides your weight, in kilograms, by the square of your height, in metres.
BMI = weight (kg) ÷ height² (m)For example, with 70 kg and 1.75 m: 70 ÷ (1.75 × 1.75) = 22.9. This BMI falls within a healthy weight.
| Category | BMI |
|---|---|
| Underweight | < 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obesity, class I | 30 – 34.9 |
| Obesity, class II | 35 – 39.9 |
| Obesity, class III | ≥ 40 |
These thresholds are those of the World Health Organization.
What BMI does not tell you
BMI is simple and useful across a population, but for one person it remains a landmark:
- it does not tell muscle from fat: a very muscular person can have a high BMI without excess fat;
- it does not say where fat sits, while waist size matters too;
- it does not apply as such to children and teenagers, nor during pregnancy.
Healthy weight by height
This table gives, for each height, the weights that match a BMI of 18.5 to 24.9.
| Height | Healthy weight |
|---|---|
| 150 cm | 41.6 – 56.0 kg |
| 155 cm | 44.4 – 59.8 kg |
| 160 cm | 47.4 – 63.7 kg |
| 165 cm | 50.4 – 67.8 kg |
| 170 cm | 53.5 – 72.0 kg |
| 175 cm | 56.7 – 76.3 kg |
| 180 cm | 59.9 – 80.7 kg |
| 185 cm | 63.3 – 85.2 kg |
| 190 cm | 66.8 – 89.9 kg |
| 195 cm | 70.3 – 94.7 kg |
| 200 cm | 74.0 – 99.6 kg |
Frequently asked questions
For adults, the World Health Organization places a healthy weight between 18.5 and 24.9. Below that is underweight; from 25, overweight; from 30, obesity.
Divide your weight in kilograms by your height in metres multiplied by itself. For 80 kg and 1.80 m: 80 ÷ (1.80 × 1.80) = 24.7. The calculator on this page does it for you, in metric or imperial units.
Yes, the formula and the thresholds are the same for adult women and men. BMI does not, however, account for body composition, which differs from one person to another.
Not as such. For children and teenagers, BMI is read on growth charts by age and sex. A doctor or paediatrician can interpret it.
BMI is a starting point. Talk to a health professional, who will look at your situation as a whole before advising you.
Weight loss simulator
Say where you stand and where you want to go: the simulator estimates the time it takes at a reasonable pace.
An estimate from a steady pace: your real weight moves from one week to the next. This tool does not replace the advice of a health professional.
Why Slyra can help you lose weight
This simulation shows where you can go. The Slyra programme helps you get there, meal after meal.
Targets worked out for you
Your calories and macros start from your body, your activity and the pace you choose, not from one plan for everyone.
Your meals noted in seconds
Search for a food or scan its barcode. In a study of nearly 1,700 adults, those who kept a food record every day lost twice as much weight as those who kept none (Hollis, 2008).
A method, not a diet
Nothing is forbidden: you keep what you like and see each day where you stand. Studies find that up to two thirds of dieters regain more weight than they lost (Mann, 2007).
Your weigh-ins against your curve
Each weigh-in shows whether you are ahead of the path you chose or behind it, so you can adjust early. Sleep, activity and water are followed in the same place.
These studies are about food tracking and diets in general, not about Slyra. Results vary from one person to another.
Track your weight and your calories
Slyra tracks your weight, your meals and your macros day by day. Free to start.