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
What is Half a Stone in Kilograms?
Half a stone is a common UK weight measurement equal to 3.18 kilograms or 7 pounds. In the UK, we often talk about weight loss and body weight in stone and pounds rather than kilograms, which can make it confusing when using NHS health guidance or comparing with international measurements. Understanding how to convert between these units helps you track your weight and assess your health using our UK health information resources and NHS guidance.
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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.
Half a Stone Conversion and UK Health Context
Half a stone = 3.18 kg (or 3,180 grams)
To convert stone to kilograms, divide by 6.35029. Half a stone therefore equals 0.5 × 6.35029 = 3.175 kg, commonly rounded to 3.18 kg. Conversely, 3.18 kg equals approximately 0.5 stone or 7 pounds exactly.
In UK health guidance, the NHS uses kilograms for clinical measurements and health records, but most UK adults naturally think about weight in stone and pounds. This means you may need to convert when consulting health charts or using our free weight converter. Understanding both measurements is useful for weight management, as half a stone (3.18 kg) represents a modest but meaningful weight change — roughly equivalent to losing or gaining the weight of a large bag of sugar.
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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.
Using Half a Stone in Weight Loss and Health Planning
If you're tracking weight loss or gain, half a stone is a realistic milestone. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results, meaning losing half a stone would take 3–6 weeks of steady, healthy weight loss. For health context, losing half a stone can improve blood pressure, reduce strain on joints, and lower your risk of type 2 diabetes — even small weight reductions have measurable health benefits.
Use our free BMI calculator above to see how losing or gaining half a stone would affect your BMI, or try our weight converter to compare different measurements as you plan your health goals. Always speak to your GP if you're making significant changes to your weight or diet.
- 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.
How many kilograms is half a stone?
Half a stone equals 3.18 kilograms (or 3,180 grams). Since one stone is 6.35 kg, half a stone is simply 6.35 ÷ 2 = 3.18 kg. This is the standard metric conversion used in NHS health records and clinical settings across the UK.
What is half a stone in pounds?
Half a stone equals exactly 7 pounds. One stone is always 14 pounds, so half a stone is 14 ÷ 2 = 7 lbs. This conversion is exact and doesn't require rounding, making it easy to remember for UK measurements.
Is losing half a stone a healthy weight loss goal?
Yes, losing half a stone (3.18 kg) is a realistic and healthy goal. The NHS recommends losing 0.5–1 kg per week, so half a stone would represent 3–6 weeks of steady progress. Even modest weight loss of 5–10% of body weight can improve blood pressure, blood sugar, and joint health.
How do I calculate my BMI after losing half a stone?
Use our free BMI calculator on this page to instantly recalculate your BMI after losing half a stone. You can enter your current weight and then subtract 3.18 kg to see how this change would affect your BMI. This helps you understand whether losing half a stone would move you closer to a healthy weight range.
Why does the UK use stone for weight instead of kilograms?
The UK traditionally uses imperial measurements including stone and pounds for everyday weight discussions, even though kilograms are used in medical and scientific contexts. This is historical — the stone remains culturally embedded in UK health conversations, which is why NHS health information often needs to be converted between units for practical use.
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.