Protein Intake Calculator: find your daily protein needs

Our Protein Intake Calculator estimates how many grams of protein you should aim for each day, based on your bodyweight, activity level, and health goal. Getting enough protein is especially important if you are losing weight — including on GLP-1 medications such as semaglutide or tirzepatide — because adequate intake can help preserve lean muscle mass. Enter your details above to get a personalised target in seconds.

How to use the Protein Intake Calculator

To get your result, enter your current bodyweight (in kilograms or pounds), select your typical activity level, and choose the goal that best describes you — for example, general health, weight loss, or muscle building. The Protein Intake Calculator will then display a recommended daily protein range expressed in grams and in grams per kilogram of bodyweight (g/kg). If you are unsure of your activity level, choose the option that reflects your average week rather than your best week.

Your result is a starting point, not a rigid prescription. Protein needs can vary depending on age, health status, and how quickly you are losing weight. We recommend revisiting the calculator if your bodyweight changes by more than five kilograms, or if your activity level shifts significantly — for instance, if you begin or stop a structured exercise programme.

What the Protein Intake Calculator's results actually mean

The calculator outputs a daily protein target expressed as a range — for example, 100–130 g per day. This range reflects the variation in guidance across different health goals and the fact that protein requirements are not a single fixed number. Below is a summary of the typical g/kg benchmarks used in the calculator, based on current evidence and recognised nutritional guidelines.

• Sedentary adults (general health): approximately 0.8–1.0 g/kg bodyweight per day — the level recommended by the UK Reference Nutrient Intake (RNI) for maintenance.
• Active adults or those doing regular resistance training: approximately 1.4–1.7 g/kg per day to support muscle repair and adaptation.
• Adults in a calorie deficit (weight loss): approximately 1.2–1.6 g/kg per day to help preserve lean muscle while body fat is reduced.
• GLP-1 medication users (e.g. semaglutide, tirzepatide): many clinicians recommend targeting the higher end of the weight-loss range — 1.5–2.0 g/kg — because appetite suppression can make it harder to meet protein targets through normal eating.
• Older adults (65+): approximately 1.0–1.2 g/kg per day at minimum, as protein synthesis becomes less efficient with age and sarcopenia risk increases.

Why protein matters on GLP-1 medications — the science behind the calculator

GLP-1 receptor agonists such as semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro) work partly by reducing appetite and slowing gastric emptying, which leads to a significant reduction in overall calorie intake. Rapid weight loss from any cause — including GLP-1-assisted weight loss — carries a risk of losing lean muscle mass alongside body fat. Research suggests that without adequate protein intake and some form of resistance exercise, a meaningful proportion of weight lost during calorie restriction can come from muscle rather than fat alone.

How protein helps preserve muscle during weight loss

Protein provides amino acids that act as the building blocks for muscle tissue. When you are in a calorie deficit, your body can break down muscle protein for energy if dietary protein is insufficient — a process called muscle protein catabolism. Consuming enough protein throughout the day stimulates muscle protein synthesis (MPS), which can help offset this breakdown and preserve functional muscle mass even while overall bodyweight falls.

For GLP-1 users in particular, the challenge is that appetite suppression may make it difficult to eat enough food to hit a protein target, especially in the early weeks of treatment. Prioritising protein-dense foods — such as chicken, fish, eggs, Greek yoghurt, cottage cheese, legumes, and protein supplements if needed — at each meal can help ensure the target from the Protein Intake Calculator is met even when overall food volume is low.

Protein Intake Calculator results: putting your number into practice

Once you have your daily protein target, the most practical approach is to spread intake across three to four meals or snacks rather than trying to consume it all in one sitting. Research indicates that muscle protein synthesis responds better to evenly distributed protein doses of roughly 25–40 g per meal than to one or two very large servings. For a target of 120 g per day, for example, this might look like 30 g at breakfast, 35 g at lunch, 35 g at dinner, and a small protein-rich snack in between.

If you find it consistently difficult to reach your target through whole foods alone — which is common for GLP-1 users with reduced appetite — a protein supplement such as whey, casein, or a plant-based blend can bridge the gap without requiring a large volume of food. However, supplements are not a replacement for a varied, nutrient-rich diet. If you have kidney disease, liver conditions, or other medical concerns, speak to your GP or a registered dietitian before significantly increasing your protein intake, as very high intakes may not be appropriate for everyone.

Frequently Asked Questions

Sources

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5. Stokes T et al. — Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy with resistance exercise training Nutrients (PubMed) [accessed 26 August 2026]
6. Wilkinson DJ et al. — Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism Journal of Physiology (PubMed) [accessed 26 August 2026]
7. Obesity: identification, assessment and management — Clinical guideline CG189 NICE (National Institute for Health and Care Excellence) [accessed 26 August 2026]
8. Lim J et al. — Preserving muscle mass during weight loss with GLP-1 receptor agonists: a narrative review PubMed / National Library of Medicine [accessed 26 August 2026]
9. Paddon-Jones D et al. — Protein and healthy aging American Journal of Clinical Nutrition (PubMed) [accessed 26 August 2026]
10. Eat well — The Eatwell Guide NHS [accessed 26 August 2026]

This calculator provides an estimate for general informational purposes only and is not medical advice. Always consult a qualified healthcare professional before making changes to your diet or starting any weight loss treatment.