Free Tool · Instant Result
BMI Calculator
Work out your Body Mass Index in seconds — in metric or imperial units — and see what it means for your weight-loss options.
THE BASICS
What is Body Mass Index?
BMI is the most widely used screening tool to assess whether your weight is in a healthy range for your height — used by the NHS, GPs and bariatric specialists worldwide. It's a simple calculation (weight in kg ÷ height in m²) that gives a single number representing where you stand. It isn't perfect, but it's the standard starting point for every weight-loss surgery conversation.
THE CATEGORIES
What does your BMI score mean?
Below 18.5 — Underweight: May indicate undernutrition or an underlying condition. Can weaken immunity and bone health — worth discussing with your GP.
18.5–24.9 — Healthy weight: The range associated with the lowest risk of weight-related disease. Maintenance is the goal.
25–29.9 — Overweight: Elevated risk of type 2 diabetes and heart disease. Lifestyle changes are first-line; the Allurion balloon can support them.
30–34.9 — Obese Class I: Health risks rise significantly. Surgery becomes an option — especially with conditions like diabetes, hypertension or sleep apnoea.
35–39.9 — Obese Class II: The range where gastric sleeve and bypass are strongly indicated by international criteria.
40+ — Obese Class III: Bariatric surgery is a well-established, evidence-backed treatment with strong long-term outcomes.
NHS vs TURKEY
Bariatric surgery criteria: NHS vs Turkey
Why are the criteria more flexible in Turkey? The NHS has limited resources and must prioritise the most severe cases. Private clinics in Turkey follow international standards — similar to private UK clinics — and accept patients earlier in their obesity journey, when intervention is often more effective and prevents serious complications.
YOUR OPTIONS
Which procedure is right for your BMI?
BMI 27–35 · Allurion Gastric Balloon: A swallowable balloon that fills your stomach for 16 weeks, then passes naturally. No surgery, no anaesthesia — typical loss of 10–15 kg. Learn more →
BMI 30+ · Gastric Sleeve: The most popular bariatric procedure worldwide — 60–70% of excess weight typically lost within 12–18 months. Learn more →
BMI 35+ · Gastric Bypass: Powerful metabolic surgery — 70–80% of excess weight, with strong results for type 2 diabetes. Learn more →
KNOW THE LIMITS
When BMI doesn't tell the full story
Muscle vs fat: Athletes often score "overweight" due to muscle, not fat — a 95 kg muscular person at 1.80 m isn't obese in any meaningful sense.
Fat distribution: BMI ignores where fat sits — abdominal fat carries higher metabolic risk than the same weight on hips and thighs.
Age & ethnicity: Older adults and some ethnic groups face different risk thresholds — people of Asian descent may face risks from BMI 23+.
BMI also isn't designed for pregnant women or under-18s. That's why final eligibility is never decided by the number alone — your free assessment reviews your full health profile.
BMI QUESTIONS
Frequently asked questions about BMI
What is a healthy BMI for adults?
For adults 18+, a healthy BMI is between 18.5 and 24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is classified as obese — the ranges used by the NHS and WHO. Ethnicity can shift these thresholds: people of Asian descent may face health risks from BMI 23+.
What BMI do I need for gastric sleeve surgery in Turkey?
At NewMe, we accept patients with a BMI of 30+, or 27+ with an obesity-related condition such as type 2 diabetes, hypertension or sleep apnoea — more flexible than NHS criteria (typically 40+, or 35+ with comorbidities). Final eligibility is always confirmed by a doctor during your free consultation.
Can I have weight loss surgery with a BMI below 30?
In some cases, yes. With BMI 27–29.9 plus obesity-related conditions, you may qualify for surgery. For BMI 25–29.9 without comorbidities, the Allurion gastric balloon is often the better option — non-surgical, with typical loss of 10–15 kg.
Why does the NHS require BMI 40+ when private clinics accept 30+?
The NHS has limited resources and must prioritise the most severe cases. Private clinics in Turkey follow international standards — similar to private UK clinics — where earlier intervention is considered preventive medicine, often producing better outcomes before serious complications develop.
Is BMI accurate for muscular people or athletes?
No. BMI can't distinguish muscle from fat, so a muscular athlete may score "overweight" with low body fat. For these individuals, body-fat percentage, waist circumference and fitness assessments give a truer picture.
How do I calculate BMI manually?
Metric: weight (kg) ÷ height (m)². Example: 80 kg at 1.75 m → 80 ÷ 3.0625 = 26.1. Imperial: (pounds ÷ inches²) × 703. Or just use the calculator above — it handles both.
How much weight will I lose with bariatric surgery?
It varies by procedure: Allurion balloon 10–15 kg over 16 weeks; gastric sleeve 60–70% of excess weight (typically 30–50 kg) within 12–18 months; gastric bypass 70–80% within 18–24 months. Long-term success depends on lifestyle change — which is why our packages include 12 months of structured aftercare.
What if my BMI is borderline — say 29.9 or 30.1?
A borderline number shouldn't decide alone. We look at your complete profile: waist circumference, blood pressure, cholesterol, insulin resistance, family history and quality of life. If you're near a threshold, a free consultation gives you an honest recommendation — whether that's lifestyle change, the balloon or surgery.
Does my BMI need to drop before surgery?
For most patients, no. With very high BMI (50+) or significant fatty liver, your surgeon may recommend a 2–4 week liver-shrinking diet before surgery for safety — assessed during your consultation, with a specific plan provided if needed.
What's the next step after calculating my BMI?
Book a free consultation via WhatsApp or our contact form. Our team reviews your medical history, you speak with a bariatric surgeon by video, and if suitable you receive a personalised treatment plan and written quote. No obligation — consultations are completely free.
Not sure what your result means for you?
Send us your height, weight and health history — our medical team reviews it for free and tells you honestly whether surgery is right for you.
