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
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Weight Percentile Girl Calculator — UK Health Guide
Understanding your daughter's weight percentile is an important part of monitoring her healthy growth and development. In the UK, healthcare professionals use NHS growth reference charts to assess whether children are growing at a healthy rate for their age and height. Unlike adult weight assessment, children's weight is never evaluated using adult BMI categories — instead, percentile rankings compare your daughter's weight against hundreds of other children of the same age and sex. This guide explains how weight percentiles work, what NHS guidance says, and how to use growth charts to support your child's health.
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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.
Understanding Weight Percentiles for Girls — NHS Guidance
A weight percentile tells you how your daughter's weight compares to other girls of the same age. For example, if she is at the 50th percentile, her weight is typical for girls her age — half weigh more, half weigh less. The UK uses the UK90 growth reference charts, which were developed by the Medical Research Council and are based on measurements from thousands of UK children.
- Below 2nd centile: Underweight — your GP may want to monitor growth
- 2nd to 91st centile: Healthy weight range
- 91st to 98th centile: Very overweight — GP review recommended
- Above 98th centile: Severely overweight — GP involvement suggested
It's important to note that a single measurement is less significant than growth trend over time. Your health visitor or GP tracks your daughter's growth pattern using a growth chart — consistency matters more than a single reading. Children naturally vary in when they gain height and weight, and this variation is completely normal.
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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.
What NHS Health Visitors and GPs Look For
In the UK, health visitors routinely assess children's growth at scheduled appointments (often at 8 weeks, 1 year, 2–2.5 years, and school entry). They plot weight, height, and head circumference on official NHS growth charts to identify any concerning patterns. A child crossing percentile lines upwards or downwards significantly may warrant further investigation for underlying causes like nutritional issues, absorption problems, or hormonal imbalances.
If you have concerns about your daughter's weight or growth, your first step is always to speak with your health visitor or GP — they have access to her complete growth history and can provide personalised advice. Never attempt to put a child on a weight loss diet without professional guidance. Instead, focus on supporting healthy habits: regular physical activity, balanced nutrition, adequate sleep, and limiting sugary drinks and ultra-processed foods. Your MyWeightCheck BMI calculator can help you understand adult weight context, but for children, growth charts and professional assessment are always the right approach.
- 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 weight percentile and BMI for children?
BMI categories used for adults do not apply to children. Instead, children's weight is assessed using age and sex-specific percentile charts. A child at the 75th percentile for weight is not "overweight" — percentiles simply show how her weight compares to peers. Only health professionals interpreting growth trends can identify if there's a health concern.
Should I use an online weight percentile calculator for my daughter?
Online calculators can give approximate guidance, but they cannot replace professional assessment. Your health visitor or GP has access to official UK90 growth charts and your daughter's individual growth history. Always discuss any concerns with your GP rather than relying solely on online tools.
What should I do if my daughter is above the 98th percentile for weight?
Speak with your GP or health visitor. They will assess your daughter's overall health, growth pattern, and any underlying factors. Most children above this centile do not need treatment, but your GP can provide personalised advice. Never start a child on a restrictive diet without professional guidance.
How often should my daughter's weight be checked?
UK health visitors typically check weight at scheduled appointments in early childhood (8 weeks, 1 year, 2–2.5 years, and school entry). After this, weight checks are usually part of routine school health assessments or GP visits. If there are concerns, your GP may recommend more frequent monitoring.
Can weight percentile change as my daughter grows?
Yes, it's completely normal for a child's percentile to shift as she grows. Growth happens in spurts, and children naturally vary in their growth patterns. What matters is the overall trend — consistent growth along a percentile line is reassuring, whereas a sudden upward or downward shift might prompt your GP to investigate further.
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.