Macro Calculator
Work out your maintenance calories and daily macros. Body fat is optional, but supplying it switches the estimate to a more accurate lean-mass-based formula.
Years
If you know it, the calculator uses Katch-McArdle instead - it works from lean mass, so it is more accurate.
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Medical disclaimer: These figures are population-level estimates, not a prescription. Individual energy needs vary by up to 20% from any predictive equation. This tool does not provide medical advice, diagnosis, or treatment. Consult a qualified physician or registered dietitian before starting or changing any diet, especially if you have a medical condition, are pregnant, or have a history of disordered eating. If you experience adverse effects, stop and seek medical attention.
How to use these numbers
Treat the results as a starting estimate, not a target to hit exactly. The point is to give you a sensible place to begin and something to adjust from.
- Start at the estimate for your goal and keep the rest of your routine steady for two to three weeks.
- Track the trend, not the daily number: weigh in a few times a week and watch the weekly average.
- Adjust gradually if the trend isn't moving the way your goal expects — small changes, not big swings.
- Protein and overall energy matter most; carbs and fat can flex around your preferences and training.
- If you have, or are prone to, disordered eating, don't use calorie or macro targets — speak to a qualified professional instead.
Macro calculator FAQ
- How accurate is this macro calculator?
- It uses well-established equations (Mifflin-St Jeor, or Katch-McArdle when you supply body fat), but every predictive formula is an estimate — real energy needs can vary by around 20% between people. Use the result as a starting point and refine it from your own results over a few weeks.
- Should I use Mifflin-St Jeor or Katch-McArdle?
- If you don't know your body fat percentage, the calculator uses Mifflin-St Jeor. If you do, it switches to Katch-McArdle, which works from lean mass and is usually the more accurate of the two.
- How much protein do I need?
- Protein is usually set relative to your bodyweight, and the calculator estimates a sensible amount from your inputs. It helps preserve muscle when you're eating less and supports building it when you're eating more, which is why it's the macro worth being most consistent with.
- Should I eat in a deficit or a surplus?
- That depends on your goal: a modest deficit for fat loss, maintenance to hold steady, or a modest surplus to gain. Change slowly and reassess from the trend. This isn't medical advice — if you're unsure or have a health condition, check with a professional first.
- How often should I recalculate?
- Recalculate when your weight, activity level or goal changes meaningfully. Day-to-day fluctuations don't need a new calculation; a shift of a few kilos or a real change in training does.