Using a Wegovy weight loss calculator: what the numbers actually mean

Step 1: understand what the calculator is actually doing

Most Wegovy or semaglutide weight loss calculators work the same way. You enter your current weight, and the tool multiplies it by a percentage taken from published trial data, most often the ~15% average body-weight reduction seen over 68 weeks in the STEP 1 trial published in the New England Journal of Medicine. Some tools also offer a higher figure for users who ask about the newer 7.2 mg dose, where trials reported around 20.7% average loss over 72 weeks.

That arithmetic is simple and transparent. If you weigh 110 kg and the calculator applies a 15% average, it returns 16.5 kg lost. What no calculator can factor in: whether you'll reach and tolerate the maintenance dose, how your appetite responds to semaglutide specifically, any medicines you already take, or the quality of the dietary and activity support you have around you. The result is a benchmark for a hypothetical average person, not a forecast for you.

There is also a category of tools sometimes labelled a semaglutide calculator online that is aimed at compounding pharmacies or research contexts, not licensed UK prescribing. These use entirely different concentration maths and are not relevant to Wegovy prescribed through a UK pharmacy.

Step 2: know which dose the average was calculated at

The figure a standard wegovy weight loss calculator free tool uses is almost always the 2.4 mg maintenance-dose result from STEP 1. But reaching 2.4 mg takes roughly five months of careful titration: 0.25 mg for four weeks, then 0.5 mg, 1.0 mg, 1.7 mg, and finally 2.4 mg, each step held for around four weeks under prescriber oversight. Some people need a longer time at an earlier dose because of gastrointestinal side effects (nausea, loose stools, or reflux) that ease once the body adjusts.

The MHRA approved a single-dose 7.2 mg Wegovy pen on 14 April 2026, intended for adults with a BMI of 30 or above, with titration still starting at 0.25 mg. That higher maintenance dose narrows the gap in average results that had previously made tirzepatide stand apart. You can read more about how Wegovy's clinical evidence compares on our Wegovy treatment overview. A semaglutide dosing calculator aimed at UK Wegovy patients should always reflect this licensed titration schedule, if it doesn't, treat the output with scepticism.

One point worth making plainly: a calculator cannot tell you which dose you'll actually reach. That is a clinical conversation, revisited at each review.

Step 3: put the number in context alongside real eligibility factors

Suppose the tool gives you a figure you find encouraging. The next practical question is whether Wegovy is clinically suitable for you at all. NHS guidance on semaglutide confirms it is licensed for adults with a BMI of 30 or above, or 27 to 29.9 where at least one weight-related condition is present, such as high blood pressure, type 2 diabetes, or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance.

Eligibility also depends on your medical history. A history of pancreatitis, medullary thyroid carcinoma, or certain gastrointestinal conditions requires careful prescriber discussion. Wegovy is not recommended during pregnancy, while breastfeeding, or for anyone trying to conceive. These are not calculator fields; they are clinical judgements that sit with a prescriber, not a spreadsheet.

There is also a cost dimension worth reading before you proceed. Our Wegovy price comparison page sets out the range of private treatment costs honestly, including what a legitimate price should include: clinical assessment, prescription, aftercare, and delivery. A calculator that outputs a weight figure but not a cost figure is only telling you half a story.

Step 4: what comes after the estimate

If a rough Wegovy weight loss calculator result has you thinking seriously about treatment, the next step is a proper clinical consultation rather than more calculation. At nume, a GPhC-registered Independent Prescriber reads your answers personally the same day, not software making an automated call. Photo-ID checks, live weight verification, and a review of your full medical picture happen before any prescription is issued.

If approved, treatment arrives with DPD tracking to your door the next working day, in plain packaging with nothing on the outside to indicate what's inside. You get one transparent price covering consultation, prescription, and delivery, no subscription and no auto-renewal, with a clinical review before every repeat order.

For a broader view of how semaglutide works and what the treatment journey involves, our semaglutide overview page covers the mechanism, evidence and practical details. If you are moving through the titration stages and want to work out your next injection amount, our peptide calculator for semaglutide can help you check the numbers before your next dose. If you have questions about the process before starting, our FAQs address the ones we hear most often.

A calculator gives you a number. A prescriber gives you a plan. Before you book a consultation, it is worth understanding what the step 8 semaglutide stage of the titration schedule involves, so you know what the full treatment arc looks like from the outset. Check your eligibility with our clinical team to see whether Wegovy is the right route for you.