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
Weight Maintenance Calculator — Keep Your Weight Stable
A weight maintenance calculator helps you determine how many calories you need daily to keep your weight steady once you've reached your target. Unlike weight loss (which requires a calorie deficit), maintenance means eating enough to match your energy expenditure. This is a crucial phase after losing weight — many people find maintenance harder than the initial loss. Understanding your personal calorie needs makes staying at a healthy weight much easier. Our free BMI calculator and weight converter help you track where you sit on the healthy weight range for your height, whilst our progress tracker lets you monitor stability over time.
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 Calculate Your Maintenance Calories
Your maintenance calorie needs depend on your basal metabolic rate (BMR) — the calories your body burns at rest — multiplied by your activity level. The most common approach uses the Harris-Benedict equation or Mifflin-St Jeor formula to estimate BMR, then multiplies by an activity factor:
- Sedentary (little exercise): BMR × 1.2
- Lightly active (1–3 days exercise/week): BMR × 1.375
- Moderately active (3–5 days/week): BMR × 1.55
- Very active (6–7 days/week): BMR × 1.725
- Extremely active (intense daily exercise): BMR × 1.9
As an example, a 70kg adult of average height with moderate activity typically needs approximately 2000–2400 kcal daily for maintenance — though this varies significantly based on age, sex, and muscle mass. The NHS advises that average adult women need around 2000 kcal and men around 2500 kcal daily, though individual needs differ considerably.
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.
Weight Maintenance vs Weight Loss
Once you've lost weight successfully, your calorie needs actually decrease because your body is now smaller and requires less energy. This is why people often regain weight — they return to eating as they did before the loss, forgetting that their body now needs fewer calories. To maintain, you must eat the amount needed for your current weight, not your previous weight. If you've lost 10kg, you'll need roughly 200–300 fewer calories daily than you did before the loss. Use our BMI calculator to check whether your current weight sits within a healthy range for your height according to NHS guidelines, then adjust your intake accordingly to stay stable there.
- 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's the difference between maintenance calories and calories to lose weight?
Weight loss requires eating 500 kcal less than you burn daily (roughly 0.5kg loss per week). Maintenance means eating exactly what you burn. Eating above maintenance causes weight gain. The NHS recommends losing weight at 0.5–1kg weekly, then switching to maintenance at your target weight to prevent regain.
How do I know my current maintenance calorie level?
Track your actual food intake for 1–2 weeks while weighing yourself daily. If your weight stays stable, your average daily intake is approximately your maintenance level. Use our progress tracker to monitor weekly weight trends and spot your stability point. Individual variation is significant — tracking real data beats any calculator estimate.
Does maintenance get easier over time?
Yes. After 6–12 weeks eating at maintenance, your body adapts and maintaining becomes automatic. Many people stop actively counting calories once they understand portion sizes for their body. However, returning to old habits (stress eating, portion creep) is the most common cause of weight regain — awareness remains important long-term.
Should I use a weight maintenance calculator app or tool?
Calculators give you a useful starting point (typically within 10–15% of your true needs), but individual tracking is most accurate. MyWeightCheck's free weight converter and BMI calculator help you understand your healthy weight range and current status. Combine calculator estimates with 2–4 weeks of real-world tracking to find your true maintenance level.
What if I gain or lose weight during maintenance?
Small fluctuations (±2kg) are normal due to water retention, digestion, hormones, and salt intake — they're not fat gain. If you consistently gain over 2 weeks, you're eating above maintenance and should slightly reduce portion sizes. If you're losing despite wanting stability, increase calories by 100–200 kcal daily and reassess after 2 weeks.
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.