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
Body Fat Calculator — What You Need to Know
A body fat calculator helps you measure the percentage of fat in your body, which goes beyond what BMI alone can tell you. Unlike BMI, body fat percentage distinguishes between muscle and fat — two very different things. The NHS recognises that body composition matters for overall health, and understanding your body fat percentage can help you set more accurate health goals. Even if your BMI falls in the healthy range, high body fat with low muscle can still pose health risks. This guide explains how body fat calculators work, what healthy ranges look like in the UK, and why body composition monitoring complements other health measurements.
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 Body Fat Percentage Is Calculated
Body fat percentage is estimated using several methods, each with varying accuracy levels. The most common UK approaches include:
- DEXA scan (gold standard) — Medical imaging that measures body composition precisely; typically available through private health clinics or research facilities
- Bioelectrical impedance analysis (BIA) — Handheld devices or scales that send a small electrical current through your body to estimate fat, water, and muscle; reasonably accurate if well-calibrated
- Skinfold calipers — A trained professional measures fat folds at specific body sites; accuracy depends heavily on the practitioner's skill
- Anthropometric formulas — Equations using height, weight, age, and gender to estimate body fat; these are approximations rather than measurements
Most home body fat calculators use anthropometric formulas or bioelectrical impedance because they're non-invasive and accessible. However, they're estimates only — they cannot be as precise as medical imaging. For consistent tracking, use the same method each time.
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.
Healthy Body Fat Ranges and What They Mean
The NHS and fitness professionals recognise these approximate body fat percentage ranges as healthy:
- Women: 21–31% = acceptable range; 14–20% = athletic; below 13% = essential fat only (not sustainable)
- Men: 18–24% = acceptable range; 6–13% = athletic; below 5% = essential fat only (not sustainable)
Body fat percentage is more informative than BMI alone because it reveals whether weight comes from muscle or fat. Two people with the same BMI can have completely different body compositions. Use our free BMI calculator alongside body fat assessment for a fuller picture of your health. If you're concerned about your body composition, your GP can refer you to a nutritionist or personal trainer for personalised guidance on healthy targets for your age and fitness level.
- 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 a good body fat percentage?
According to fitness and health standards, healthy body fat ranges are 21–31% for women and 18–24% for men. Athletic individuals may have lower percentages (14–20% for women, 6–13% for men). Below these ranges indicates very low body fat, which isn't sustainable. Your ideal percentage depends on age, genetics, and fitness goals — discuss targets with your GP or a qualified fitness professional.
Is body fat percentage more important than BMI?
They measure different things. BMI shows whether weight is in a healthy range for your height; body fat percentage reveals whether that weight is muscle or fat. Someone can have a healthy BMI but high body fat (poor fitness), or a higher BMI with low body fat (muscular). Together, they give a fuller health picture. Use our BMI calculator and body fat assessment together for best results.
How accurate are home body fat calculators?
Home calculators using bioelectrical impedance or formula-based estimates are reasonably accurate for tracking trends but not as precise as medical imaging (DEXA scans). Accuracy depends on the device quality and your hydration level. For consistency, use the same calculator method each time. If you need clinical-grade accuracy, ask your GP about DEXA scanning availability in your area.
Can I reduce my body fat percentage through weight loss?
Yes, but the approach matters. A calorie deficit combined with strength training helps reduce fat while preserving muscle. The NHS recommends losing 0.5–1kg per week through diet and exercise. However, gradual weight management often results in muscle loss as well as fat loss. A balanced approach with resistance exercise helps maintain muscle while reducing fat percentage.
How does body fat percentage relate to health risks?
Higher body fat percentage — especially around the abdomen — is associated with increased risk of type 2 diabetes, heart disease, and other conditions, even if BMI is normal. Waist circumference also matters: the NHS flags increased risk at over 80cm (women) or 94cm (men). Body composition assessment helps identify health risks that BMI alone might miss.
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.