BMI Calculator UK NHS 2026

Accurate body mass index tool for adults and children (2–17 years). Works with stones, pounds, kg, cm, feet & inches – fully compliant with UK guidelines.

Adult BMI Calculator (18+ years) — UK standard

Use metric or imperial units. BMI = weight (kg) ÷ height (m)². Based on NHS & WHO classification 2026.

Weight (kg)

Height (cm)

Children’s BMI Calculator UK (2–17 years)

For children and teenagers, BMI is interpreted using age- and sex-specific centile charts. Use this tool to get BMI value, then compare with NHS UK90 centiles or consult GP.

Weight (kg)

Height (cm)

Age (years, 2–17)

Sex

BMI classification for adults (UK / NHS 2026)

BMI range (kg/m²)	Classification
Below 18.5	Underweight
18.5 – 24.9	Healthy weight
25 – 29.9	Overweight
30 – 39.9	Obesity (Class I/II)
40 and above	Severe obesity

For adults of South Asian, Chinese or other black and minority ethnic groups, the healthy range is often lower (≥23 indicates increased risk). Always discuss with a UK GP.

How to calculate BMI (UK formula)

Metric: weight (kg) ÷ (height in metres)². If height in cm, divide by 100 first.
Imperial (stones/pounds): total pounds = (stones × 14) + pounds. Weight in kg = pounds × 0.453592. Height in metres = (feet × 12 + inches) × 0.0254.
📍 Use our calculator above for instant results aligned with NHS UK BMI tool.

2026 exclusive insight: According to new UK obesity strategy, waist-to-height ratio is also recommended. We suggest using BMI alongside waist measurement (waist less than half your height) for a fuller health picture.

How to accurately measure for BMI (UK guidelines)

Weigh yourself in the morning, without heavy clothing.
Height: stand straight without shoes, back against a wall.
For children: measure height using a stadiometer for precision.
Use consistent units — our calculator handles stones, pounds, cm, ft/in.

Children’s BMI (UK specific)
The child BMI centile compares your child to UK population (UK90 growth reference). If BMI is above 85th centile = overweight, above 95th = obese. Use our calculator as first step, then refer to Diabetes UK or NHS child BMI checker.

NHS UK & Evidence-Based Resources (2026)

Many users search "nhs.co.uk bmi calculator", "bmi calculator nhs uk" or "https www nhs uk live well healthy weight bmi calculator". While we provide instant accurate results, you can also visit the official NHS tool for more context. Our calculator mirrors the same BMI formula used by GPs and slimming world advisors.

NHS Live Well BMI tool – official UK health advice.

Bupa BMI calculator UK – private health insights.

Diabetes UK BMI calculator – risk assessment for type 2.

Frequently Asked Questions (BMI UK)

❓ What is the healthy BMI range for adults in the UK?
According to NHS, a healthy BMI is between 18.5 and 24.9 kg/m². However, for older adults or ethnic minorities, thresholds may differ slightly.

❓ How do I calculate my BMI in stones and feet?
Enter your weight in stones and pounds, height in feet and inches in our imperial calculator. We convert to metric automatically using UK standard conversions.

❓ Is the BMI calculator accurate for children and teens?
For children aged 2–17, BMI alone isn't enough — you need age & sex centile charts. Use our child calculator to get BMI, then check NHS child BMI centile tool for accurate percentile.

❓ Where can I find the official NHS BMI calculator?
You can visit www.nhs.uk/live-well/healthy-weight/bmi-calculator. TotalCalcHub provides identical calculations with extra features (stones, child BMI, instant categories).

❓ Why does my BMI show “overweight” but I’m muscular?
BMI doesn't distinguish muscle from fat. Athletes may have high BMI but low body fat. Consider body composition analysis or waist-to-hip ratio for deeper insight.

❓ What is the new 2026 BMI guidance for UK?
In 2026, the NHS continues recommending BMI alongside waist circumference. Our calculator reflects the latest WHO and NICE obesity guidelines.

❓ How often should I check my BMI?
If you're trying to lose or gain weight, check every 4–6 weeks. For general health, once per quarter is sufficient.

Important medical disclaimer: This BMI calculator UK provides estimations for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Always consult your GP or a registered dietitian before making health decisions. For children, always refer to NHS growth charts.