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
Mass of Calculator — UK Health Information
A mass of calculator helps you understand your body weight and health status using UK measurements. Whether you're converting between kilograms, stone, and pounds, or calculating your BMI, accurate mass calculations are essential for tracking your health. MyWeightCheck provides free UK health information and tools to help you understand what your weight means for your wellbeing, aligned with NHS guidance on healthy weight ranges.
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 Health Calculators Work
Health calculators measure and interpret your body mass using standardised formulas. Your mass (weight) combined with your height determines your BMI (body mass index), which is the primary UK health screening tool used by the NHS. Our free BMI calculator uses the metric formula: BMI = weight (kg) ÷ height (m)². According to NHS guidelines, a healthy BMI falls between 18.5 and 24.9 for most adults, though lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults due to higher health risks at lower BMI levels.
- Mass measurements use kilograms as the standard unit in NHS clinical settings
- UK adults often prefer stone and pounds — our weight converter switches between all three instantly
- BMI categories range from underweight (below 18.5) through healthy weight, overweight, obese, and severely obese (40+)
- Your mass alone doesn't determine health risk — waist circumference and body composition also matter
For personalised UK health guidance about your weight, your GP can provide advice tailored to your individual circumstances, medical history, and health goals.
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 Tools and Resources for Weight Management
MyWeightCheck provides several free UK health information tools to help you understand your mass and weight status. Our free BMI calculator instantly shows whether your weight falls in the healthy, overweight, or obese ranges according to NHS guidelines. The weight converter tool lets you switch between kilograms, stone, and pounds — essential since UK adults use different measurements. For those considering weight management or GLP-1 medications like Mounjaro or Wegovy, our weight loss calculator can help project potential outcomes. If you're concerned about your weight or have health conditions related to excess weight, speaking with your GP is always the best first step toward personalised support and guidance.
- 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 the difference between mass and weight in health calculations?
In everyday health contexts, "mass" and "weight" are used interchangeably. Mass refers to the amount of matter in your body (measured in kg), while weight technically includes gravitational force. For UK health calculations, your mass in kilograms is what matters for BMI and NHS health assessments.
How accurate is BMI as a health measurement?
BMI is a useful screening tool approved by the NHS, but it has limitations. It doesn't distinguish between muscle and fat — athletes may have high BMI but low body fat. BMI also doesn't account for where fat is stored. Your GP can assess your individual health using BMI alongside waist circumference and other factors.
Why do UK adults use stone and pounds instead of kilograms?
Stone and pounds are traditional UK measurements still widely used for body weight, even though the NHS uses kilograms clinically. The UK is one of few countries that maintains this dual system. Our weight converter helps you switch between kg, stone, and pounds instantly for clarity.
What should I do if my BMI suggests I'm overweight or obese?
If your BMI falls above the healthy range (18.5–24.9), speak with your GP. They can assess your individual health, discuss your medical history, and recommend appropriate support — which might include lifestyle changes, dietary advice, exercise programmes, or in some cases, prescription weight management options.
Can I use a mass calculator to estimate healthy weight for my height?
Yes. Using the BMI formula, you can calculate the healthy weight range for any height. For example, at 5ft 8in (1.73m), the healthy weight range is approximately 55–75kg (8st 10lbs to 11st 10lbs). Our free BMI calculator does this automatically — simply enter your height to find your target 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.