Body Mass Index Calculator

BMI Calculator
Stone, KG & Pounds

Calculate your Body Mass Index instantly. Enter your details below.

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Your BMI

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BMI Scale

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Important Disclaimer

This is a reference tool only. BMI is one metric among many. For personalized health guidance, consult your GP or healthcare provider.

What Is BMI?

BMI stands for Body Mass Index — a mathematical calculation based on your height and weight.

The formula:

BMI = Weight (kg) ÷ Height² (m)

If you weigh yourself in stones, this calculator converts your reading to kilograms automatically before calculating your BMI.

BMI Reference Categories

BMI Range Category
Below 18.5 Underweight
18.5 – 24.9 Normal Weight
25.0 – 29.9 Overweight
30.0 and above Obese

Healthy Weight by Height

Weight ranges for a BMI of 18.5–24.9. Select your height:

Normal Weight Range (BMI 18.5–24.9)

52.2 kg — 70.3 kg

(8 st 3 lb — 11 st 1 lb)

Height Min (BMI 18.5) Max (BMI 24.9)
5ft 0in42.7 kg (6 st 10 lb)57.2 kg (9 st 0 lb)
5ft 2in45.6 kg (7 st 2 lb)61.2 kg (9 st 9 lb)
5ft 4in49.2 kg (7 st 10 lb)66.0 kg (10 st 5 lb)
5ft 6in ★52.2 kg (8 st 3 lb)70.3 kg (11 st 1 lb)
5ft 8in55.4 kg (8 st 10 lb)74.4 kg (11 st 10 lb)
5ft 10in58.6 kg (9 st 3 lb)78.7 kg (12 st 5 lb)
6ft 0in62.0 kg (9 st 11 lb)83.4 kg (13 st 2 lb)
6ft 2in65.4 kg (10 st 4 lb)87.9 kg (13 st 12 lb)

Quick BMI — 5ft 6in Reference

At the UK average height of 5ft 6in, use this table without calculating:

Weight BMI Category
8 st (50.8 kg)18.1Underweight
9 st (57.2 kg)20.4Normal
10 st (63.5 kg)22.6Normal
11 st (69.9 kg)24.9Normal
12 st (76.2 kg)27.2Overweight
14 st (88.9 kg)31.7Obese

BMI Limitations

BMI does not directly measure body fat, fitness, or health status. It has well-documented limitations:

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Athletes

Muscle weighs more than fat. A fit person with low body fat can register as overweight on BMI.

Muscle density
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Older Adults

Muscle reduces with age and is replaced by fat. A healthy BMI might hide an unhealthy body composition.

Age-related loss
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Pregnancy

BMI is not applicable during pregnancy. Weight gain is normal and expected.

Use pregnancy calc
🌍

Ethnic Groups

South Asian and other ethnic backgrounds face different health risks at the same BMI.

Genetic differences
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Height Extremes

BMI overestimates risk in very tall people and underestimates it in very short ones.

Math limitations
Why Does the NHS Still Use BMI? (Medical Guide) →

Frequently Asked Questions

Yes. Because muscle weighs more than fat, athletes and very muscular individuals often fall into the overweight or obese categories on a BMI chart despite having low body fat and excellent health.
BMI can be less accurate for older adults. As people age, muscle mass naturally decreases and is replaced by fat. An older person might have a 'healthy' BMI while carrying disproportionately high active fat.
No. BMI does not apply during pregnancy. Weight gain is expected and necessary for fetal development, the placenta, fluid, and changes to your own body. Use our Pregnancy Weight Gain Calculator instead.
Yes. Organizations like NICE in the UK use lower BMI thresholds for South Asian, Black, and other minority ethnic groups because these populations often face health risks at a lower BMI than white European populations.
Waist circumference measures abdominal fat. Fat stored around the organs (visceral fat) carries higher health risks than fat stored elsewhere. It is an excellent complementary measure to your BMI.
The BMI mathematical formula (weight ÷ height squared) tends to underestimate health risks in short people and overestimate them in tall people. This is a known limitation of the metric.
Technically yes, according to the standard chart. However, your individual health cannot be determined by a single number. Body composition, lifestyle, ethnicity, and waist size all play a part.
Our calculator multiplies your input in stones by 6.35029 to get kilograms, then divides that by your height in metres squared. The same standard medical formula is used.

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Medical Disclaimer: Content is for informational purposes only and does not constitute medical advice. Consult your GP for personalized health guidance.

Health Silo

Connect the conversion pages to health intent

Weight conversions often lead into BMI, healthy-range questions and pregnancy or women’s weight guidance, so those paths should stay visible.

Featured Path

How Much Should I Weigh?

Compare the number with healthy ranges.

Weight Chart for Women

Add gender-specific reference guidance.

Pregnancy Weight Gain Calculator

Handle pregnancy-specific weight questions.

KG to Stone

Return to the main conversion workflow when needed.