GLP-1 Calculators & Tools
Educational information only. These calculators provide estimates based on published clinical-trial averages and general nutritional guidance. They are not medical advice and do not replace a qualified healthcare professional. Always discuss weight-loss medication, nutrition, and eligibility with your clinician.
Four free tools to help you understand the numbers behind a GLP-1 journey — weight-loss projection from trial data, a daily protein target, a BMI and eligibility check, and an illustrative breakdown of muscle-loss risk. Enter your details, hit Calculate, and read the result alongside the context that makes it useful.
How much weight might I lose? Weight-loss projection
Based on the STEP-1 trial (semaglutide 2.4mg, ~68 weeks) and the SURMOUNT-1 trial (tirzepatide 15mg, ~72 weeks), this calculator applies each drug's average percentage weight loss to your current weight. Trial averages vary widely between individuals — use this as a directional estimate, not a promise.
Weight-loss projection
How much protein do I need? Daily protein target
On a GLP-1, eating less makes it easy to under-eat protein — which accelerates muscle loss. The general guidance for people on weight-loss medication is 1.2–1.6g of protein per kilogram of bodyweight per day. Enter your weight below to get your daily range.
Protein target
Do I qualify? BMI & eligibility checker
GLP-1 medications are generally considered for adults with a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). This tool calculates your BMI and gives you a plain-English note on where it sits relative to those general thresholds. Eligibility is always decided with a clinician.
BMI & eligibility checker
How much muscle could I lose? Muscle-loss estimator
Without resistance training and adequate protein, research suggests that roughly 20–40% of total weight lost during a calorie deficit can come from lean muscle rather than fat. With muscle-protective habits in place, that proportion drops substantially. This tool gives you an illustrative range for a planned weight loss — it is not a prediction, but it makes the stakes concrete.
Muscle-loss estimator
Frequently asked questions
Are these calculators medically accurate?
They apply published clinical-trial averages and widely used nutritional guidelines. Every individual is different — age, sex, starting weight, medication dose, adherence, diet, and activity level all influence real-world outcomes. Use the numbers as useful context, not a forecast.
Which trial data are used for the weight-loss projection?
The semaglutide figure (~15%) is based on the STEP-1 trial (Wilding et al., NEJM 2021). The tirzepatide figure (~20%) is based on the SURMOUNT-1 trial (Jastreboff et al., NEJM 2022). Both figures reflect the highest-dose arms of those trials over the full treatment period.
Should I use my current weight or goal weight for the protein calculator?
Most clinicians recommend using your current body weight (or a midpoint between current and goal) when calculating protein targets during active weight loss. The aim is to preserve lean mass, so the higher the target the better — especially on a GLP-1 where appetite suppression makes it easy to under-eat.
Does BMI alone determine GLP-1 eligibility?
No. BMI is one factor. Clinicians also consider comorbidities, cardiovascular risk, previous weight-loss attempts, medication history, and contraindications. A BMI of 27–30 may still qualify with certain weight-related conditions. Eligibility is always an individual clinical decision.
Can I prevent all muscle loss on a GLP-1?
Complete prevention is unrealistic during significant calorie restriction, but the muscle-loss proportion can be substantially reduced with resistance training 2–3 times a week and hitting a protein target of 1.2–1.6g per kilogram of bodyweight. See our guides on muscle loss on Ozempic and protein on a GLP-1 for the detail.