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 18.5kg in stone?
18.5 kilograms is equal to 2 stone and 13.0 pounds. This is a relatively light weight for most UK adults. To help you understand where this fits in terms of health, we've included our free weight converter above so you can switch between metric and imperial measurements instantly. The NHS uses kilograms for clinical purposes, but many people find stone and pounds more intuitive for tracking their weight. Knowing your weight in both units is useful when comparing health information or using different health calculators available online.
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 to convert 18.5kg to stone
Converting kilograms to stone is straightforward using a simple formula. Divide the kilogram value by 6.35029 to get the result in stone. For 18.5kg: 18.5 ÷ 6.35029 = 2.914 stone, which is 2 stone and 12.8 pounds (rounding to 13.0 lbs).
You can also convert directly to pounds: 18.5kg × 2.20462 = 40.8 pounds. Since 1 stone equals 14 pounds, you divide 40.8 by 14 to get 2.914 stone.
Quick reference for nearby weights:
- 15kg = 2st 5.6lbs
- 16kg = 2st 8.3lbs
- 17kg = 2st 11.1lbs
- 18.5kg = 2st 13.0lbs
- 19kg = 2st 15.8lbs
- 20kg = 3st 2.5lbs
- 21kg = 3st 5.3lbs
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.
18.5kg weight in healthy context
At 18.5kg, you would need to be an infant or very young child for this to be a typical healthy weight. For adult health assessment, 18.5 is actually the lower threshold for a healthy BMI — meaning an adult with a BMI of exactly 18.5 is at the boundary of the healthy weight range. However, the weight itself (18.5kg total body weight) would only be appropriate for a very young child.
Use our free BMI calculator above to check if your current weight is healthy for your height. The NHS considers a BMI between 18.5 and 24.9 healthy for most adults. If you're tracking your weight or working towards a health goal, our progress tracker can help you log changes over time and stay motivated.
- 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.
Is 18.5kg a healthy weight for an adult?
No, 18.5kg is far too light for any adult. This weight is only appropriate for infants or very young children. However, 18.5 is the BMI threshold number (not weight) that marks the start of a healthy BMI range for adults. Use our BMI calculator to find your healthy weight range based on your height.
How do I convert kilograms to stone accurately?
Divide kilograms by 6.35029 to get stone. For example: 18.5kg ÷ 6.35029 = 2.914 stone (2 stone 13 pounds). Alternatively, multiply kg by 2.20462 to get pounds, then divide by 14. Our weight converter above does this instantly for any value.
What is the formula for converting stone to kilogrammes?
Multiply stone by 6.35029. For example: 2 stone × 6.35029 = 12.7kg. If you have stone and pounds, convert like this: (stone × 6.35029) + (pounds × 0.453592) = total kilograms.
Why do UK people use stone for weight?
Stone is a traditional Imperial unit still widely used in the UK for personal weight. While the NHS uses kilograms clinically, most UK adults think of their weight in stone and pounds. It's a cultural preference — both units are equally valid, and knowing both is helpful.
What's my healthy weight range if I'm 5ft 8in tall?
At 5ft 8in (173cm), a healthy BMI weight range is approximately 55kg to 74kg (8st 10lbs to 11st 10lbs). The exact range depends on your individual body composition and health. Your GP can advise on what's healthy for you specifically. Use our free BMI calculator to enter your height and see your personalised range.
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.