The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Weight Calculator for UK Adults
A weight calculator is one of the most useful tools for understanding your health in UK context. Whether you want to check your BMI, convert between kilograms and stone, or discover your healthy weight range, our free weight calculator helps you get instant answers using NHS-aligned thresholds. Weight management is a personal health journey, and having accurate information is the first step towards making informed decisions about your wellbeing.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How UK Weight Calculators Work
Weight calculators combine your personal measurements — height, current weight, and sometimes age or sex — to generate health insights aligned with NHS guidance. The most common calculation is BMI (body mass index), which uses your weight in kilograms divided by your height in metres squared.
- BMI range: Healthy weight is 18.5–24.9 for most UK adults (lower thresholds apply for South Asian, Chinese, Black African, or Black Caribbean adults)
- Healthy weight range: Calculators show the stone and pound range that's healthy for your specific height
- Weight conversion: Instantly convert between kg, stone, and lbs — essential since UK health measurements use both metric and imperial
- Waist measurement context: Advanced calculators also assess waist circumference, which matters for cardiovascular health risk
Our free BMI calculator on this page does all of this instantly, giving you a complete picture of where your weight sits relative to NHS health thresholds.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
UK Weight Health Resources and Next Steps
Once you've used a weight calculator, the next step is understanding what your results mean for your personal health. If your BMI falls outside the healthy range, or if you're interested in weight management, your GP can provide tailored advice. The NHS offers tiered weight management support: self-help resources at tier 1, behaviour change programmes at tier 2, and specialist services at tiers 3 and 4 for those who need additional support.
You can also track your progress over time using our free progress tracker, and use our weight converter to understand your weight in both metric and imperial measurements. Remember that weight is influenced by many factors — genetics, medical conditions, medications, and lifestyle all play a role. A single weight calculator reading is informational; your GP can help interpret what it means for your individual health.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
What is a weight calculator and how does it work?
A weight calculator takes your height and weight (in kg or stone) and calculates your BMI and healthy weight range based on NHS guidelines. It uses the formula: BMI = weight (kg) ÷ height (m)². Our free tool on this page instantly shows your BMI category, whether you're underweight, healthy weight, overweight, or obese, and your personalised healthy weight range in stone and pounds.
Is BMI the only thing a weight calculator measures?
BMI is the primary measurement, but good weight calculators also consider healthy weight range for your height, waist circumference (which predicts cardiovascular risk), and ethnicity-adjusted thresholds. BMI has limitations — it doesn't distinguish muscle from fat — so it's best used alongside other health context. Your GP can assess your overall health picture.
Why does my weight calculator show different results to other sites?
Different calculators may use slightly different rounding or thresholds. MyWeightCheck uses NHS-aligned categories: 18.5–24.9 for healthy weight, with lower thresholds (18.5–22.9) for South Asian and other specified ethnic groups. Always check that your calculator uses current NHS guidance, not outdated standards.
Can I use a weight calculator to check if I need weight loss medication?
A weight calculator helps determine eligibility based on BMI, but prescription weight loss medications (like Mounjaro or Wegovy) require a clinical assessment by a prescriber or GP. Eligibility depends on BMI, health conditions, and individual circumstances. Use our free GLP-1 weight loss calculator to explore projections, but discuss options with your GP.
How often should I use a weight calculator to track my progress?
Weekly weighing is common, but healthy weight loss is 0.5–1 kg per week — so monthly tracking gives a clearer picture. Our free progress tracker helps you log weight over time and spot trends. Weight naturally fluctuates day-to-day due to water, food, and hormones, so focus on overall patterns rather than single readings.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.