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 12.3 Stone In Kilograms?
12.3 stone is equal to approximately 78.1 kilograms. This conversion uses the standard UK to metric conversion rate of 6.35029 kg per stone. Whether you're tracking your weight for health reasons, comparing measurements across different countries, or using NHS health guidelines, understanding how to convert between stone and kilograms is useful. Use our free weight converter above to switch between metric and imperial measurements instantly, or continue reading for the conversion formula and healthy weight context at this specific weight.
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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.
12.3 Stone To Kg Conversion Table And Formula
To convert stone to kilograms, multiply the number of stone by 6.35029. For 12.3 stone: 12.3 × 6.35029 = 78.1 kg.
Here's a reference table showing 12.3 stone alongside nearby values in both stone and kg to stone conversion:
- 12.0 stone = 76.2 kg
- 12.1 stone = 76.8 kg
- 12.2 stone = 77.5 kg
- 12.3 stone = 78.1 kg
- 12.4 stone = 78.7 kg
- 12.5 stone = 79.4 kg
- 12.6 stone = 80.0 kg
At this weight, your health context depends on your height. Use our free BMI calculator above to find your personal BMI and see where you fall within NHS healthy weight guidelines.
Clinically BackedWeight Loss
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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.
BMI And Healthy Weight Context At 12.3 Stone
At 78.1 kg (12.3 stone), your BMI depends entirely on your height. For example, at an average UK adult height of 5ft 9in (175 cm), a weight of 12.3 stone gives a BMI of approximately 27.1, which falls into the overweight category according to NHS guidelines. A healthy BMI is between 18.5 and 24.9. At this height, a healthy weight range is approximately 58–76 kg (9st 2lbs to 11st 13lbs). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds for health risk. Calculate your personal BMI instantly using the BMI calculator on this page to see your individual health context.
- 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 do I convert 12.3 stone to kg manually?
Multiply 12.3 by 6.35029. The answer is 78.1 kg. This is the exact standard conversion rate. You can also use our free weight converter tool above for gradual improvement across any weight value.
Is 12.3 stone a healthy weight?
It depends on your height. At 5ft 9in, 12.3 stone gives a BMI of 27.1, which is overweight. At 5ft 4in, the BMI would be 30.5, which is obese. Use our BMI calculator above with your actual height to find your personal BMI and NHS health category.
What is the formula for converting kilograms to stone?
Divide the kilogram value by 6.35029. For example, 78.1 kg ÷ 6.35029 = 12.3 stone. Our weight converter uses this exact formula and displays results instantly.
How much weight would I need to lose to reach a healthy BMI from 12.3 stone?
This varies by height and your personal healthy weight range. At 5ft 9in, losing to approximately 76 kg (11st 13lbs) would bring you into the healthy range. Your GP or our BMI calculator can help determine your personal target based on your height and health.
Is 78.1 kg considered obese?
Not necessarily — it depends on your height. At taller heights (5ft 11in+), 78 kg may be a healthy weight. At shorter heights (under 5ft 4in), it may fall into the obese category. Use our free BMI calculator to check your personal BMI and NHS weight category based on your actual height.
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.