Macro Calculator: find your protein, carbs & fat split

Our Macro Calculator works out how much protein, carbohydrate, and fat you should aim for each day based on your total calorie target, body stats, and health goal. Whether you're looking to lose weight, build muscle, or simply eat more balanced meals, getting your macronutrient split right can make a meaningful difference to your results. Enter your details above and the calculator will generate personalised macro targets in seconds.

What does the Macro Calculator actually measure?

The three macronutrients — protein, carbohydrates, and fat — provide all the energy (calories) your body gets from food. Protein and carbohydrates each supply 4 kcal per gram, while fat supplies 9 kcal per gram. Our Macro Calculator takes your total daily calorie target and divides it into recommended gram amounts for each macronutrient, based on your goal, activity level, and body weight.

Rather than following a one-size-fits-all split, the calculator adjusts the ratio to suit your specific aim. Someone focused on preserving muscle during a calorie deficit will need a higher proportion of protein than someone eating at maintenance, for example. Understanding what these numbers represent — not just following them blindly — can help you make smarter food choices day to day.

How the Macro Calculator works out your targets

The calculator first estimates your Total Daily Energy Expenditure (TDEE) — the number of calories your body burns in a day — using the Mifflin–St Jeor equation, which research consistently shows to be among the most accurate for the general population. It then applies an activity multiplier based on how often you exercise each week. Once your TDEE is established, any calorie adjustment for your goal (for example, a 500 kcal deficit for weight loss) is applied before the macro split is calculated.

• Sedentary (little or no exercise): TDEE × 1.2
• Lightly active (1–3 days of exercise per week): TDEE × 1.375
• Moderately active (3–5 days per week): TDEE × 1.55
• Very active (6–7 days of hard exercise per week): TDEE × 1.725
• Extra active (physical job or twice-daily training): TDEE × 1.9

How to use your Macro Calculator results day to day

Once the Macro Calculator has generated your targets, the most practical next step is to track your food intake for at least two to four weeks using a food diary or app. This helps you understand which foods contribute most to each macronutrient and where your current diet may be falling short. You don't need to hit your targets perfectly every single day — aiming to be within 5–10 g of each target on average across the week is a realistic and sustainable approach.

Adjusting your macros over time

Your macro targets are not fixed forever. As your body weight changes, your TDEE shifts — meaning the targets generated by the Macro Calculator today may need revisiting every four to six weeks. If weight loss stalls for two or more consecutive weeks despite consistent tracking, it is usually appropriate to reassess your calorie intake rather than immediately cutting further.

Similarly, if you increase your training volume significantly, your protein and carbohydrate needs may rise to support muscle repair and energy demands. Think of your macro targets as a starting framework rather than a permanent prescription, and adjust them gradually based on real-world results.

Macros, weight loss, and evidence-based expectations

A common misconception is that a specific macro ratio — such as low-carb or high-fat — is inherently superior for weight loss. Current evidence, including large-scale reviews published in journals such as The Lancet and JAMA, consistently shows that total calorie intake is the primary driver of weight change, while macronutrient composition influences satiety, muscle retention, and adherence. Higher protein intakes (typically 1.6–2.2 g per kg of body weight) are well-supported for preserving lean mass during a calorie deficit, which is why our Macro Calculator prioritises protein when a weight-loss goal is selected.

It is also worth noting that individual responses to different macro splits can vary considerably. Factors such as insulin sensitivity, gut microbiome composition, sleep quality, and stress levels all interact with how your body processes and stores macronutrients. If you have a medical condition such as type 2 diabetes, polycystic ovary syndrome (PCOS), or kidney disease, please speak with your GP or a registered dietitian before making significant dietary changes, as standard macro recommendations may not be appropriate for you.

Frequently Asked Questions

Sources

1. Eat well — the NHS guide to a balanced diet NHS [accessed 26 August 2026]
2. Calories — how to achieve a healthy weight NHS [accessed 26 August 2026]
3. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults (Mifflin–St Jeor validation) Journal of the American Dietetic Association [accessed 26 August 2026]
4. Dietary protein and muscle mass: translating science to application and health benefit PubMed / Nutrients [accessed 26 August 2026]
5. Effects of dietary composition on energy expenditure during weight-loss maintenance JAMA [accessed 26 August 2026]
6. Dietary macronutrients and obesity: a systematic review PubMed / Obesity Reviews [accessed 26 August 2026]
7. Protein and weight management: a review of the evidence British Nutrition Foundation [accessed 26 August 2026]
8. Physical activity guidelines for adults NHS [accessed 26 August 2026]
9. Obesity: identification, assessment and management — clinical guideline CG189 NICE [accessed 26 August 2026]
10. Dietary reference values for food energy and nutrients for the United Kingdom Scientific Advisory Committee on Nutrition (SACN) / GOV.UK [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.