BMI & healthy weight calculator

What BMI actually tells you

BMI is your weight in kilograms divided by your height in metres squared. The NHS uses it because it is quick and it tracks health risk reasonably well across large groups of people. The bands are: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and over obese.

Where it goes wrong

It cannot tell muscle from fat. A 5 ft 10 bricklayer who lifts can weigh 90 kg with a BMI of 28 and be in excellent shape; an office worker the same height and weight with very little muscle is not. If you train or do physical work, use BMI as one signal among several: waist measurement (under half your height is a good target), how your clothes fit, and what you can lift or how far you can walk without stopping.

Healthy weight range

The range above is simply BMI 18.5–24.9 converted back into kilograms for your height. It is deliberately wide - most people look and feel best somewhere in the middle, and where exactly depends on how much muscle they carry.

Turning this into a plan

If you want to lose weight, the number that matters next is calories. Run the calorie calculator to get a daily target, then read how much weight you can realistically lose in a month. If you want to build muscle without the BMI creeping into a band that worries you, that is exactly what a proper training and protein plan does.

FAQs

What is a healthy BMI in the UK?

The NHS classes 18.5 to 24.9 as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. People of South Asian, Chinese, Middle Eastern, Black African or African-Caribbean background are advised to use lower thresholds (23 for overweight, 27.5 for obese) because health risks start at a lower BMI.

Is BMI accurate if I have a lot of muscle?

No. BMI counts muscle the same as fat, so lifters and people with physical jobs often read as overweight while being perfectly healthy. Use waist size and body fat as better guides.

How is BMI calculated?

Weight in kilograms divided by height in metres squared. For example, 80 kg at 1.78 m is 80 ÷ (1.78 × 1.78) = 25.2.

How quickly can I get my BMI down?

Healthy fat loss is about 0.5 kg a week, roughly 0.15 BMI points a week for an average-height adult. Faster than that usually means losing muscle and water rather than fat.