Macro Calculator

What a macro split is

Your calorie target says how much energy to eat; your macro split says what to build it from. Carbohydrate and protein both provide about 4 kcal per gram, fat about 9. The calculator takes your target and a percentage split — carb / protein / fat — and converts each share into grams, so you have a concrete daily number for each rather than just a percentage.

Reading the presets

Balanced (40/30/30) is a general-purpose split with no particular emphasis, a reasonable default for most goals. Low-carb (25/35/40) and keto (5/25/70) shift the balance toward fat, with keto restricting carbohydrate sharply enough to be its own distinct approach. High-protein (35/40/25) prioritises protein intake, often chosen alongside resistance training or a deficit, where keeping protein high helps preserve muscle. Endurance (55/20/25) leans carbohydrate-heavy, suited to people training for long-duration sport where glycogen availability matters more. Custom sliders exist for anyone who wants a specific number rather than a preset — moving one slider redistributes the remaining two proportionally, so the total always stays at exactly 100%.

Why the floors and warnings exist

Percentages alone can hide a problem: 25% protein sounds reasonable until you realise it's 70 grams for someone who weighs 100kg and trains regularly, well under commonly cited ranges for supporting recovery and muscle maintenance. The calculator checks your actual grams per kilogram against two floors — 1.6 to 2.2g/kg if you train, 0.8g/kg as a general minimum otherwise — and against a 0.6g/kg fat floor, since very low fat intake can affect hormone production. These appear as warnings, not corrections; your chosen split is never silently overridden.

Fiber, and why it scales with calories

The fiber target uses a simple, widely cited rule: 14 grams per 1,000 kcal eaten. Scaling it to your calorie intake avoids the common problem of a single fixed number — such as "25 grams a day for everyone" — quietly being too little for someone eating 3,000 kcal and too much of a jump for someone eating 1,400.

Who this suits

Anyone who already has a calorie target — from this site's calorie calculator, a clinician, or elsewhere — and wants to plan what to actually eat, rather than just how much. It particularly suits people following a specific training or dietary approach (keto, higher-protein dieting, endurance fuelling) where the ratio matters as much as the total.

Tracking macros in practice

Grams are easier to act on than percentages once you're actually eating: a food label states protein, carbohydrate, and fat per serving directly, so hitting a gram target is mostly a matter of adding up labels across the day rather than doing percentage math at each meal. Most people find it easiest to prioritise protein first — it's the macro most consistently linked to satiety and to preserving muscle during a deficit — then fill remaining calories with carbohydrate and fat according to the chosen split and personal preference.

Limitations

There is no universally "correct" macro split — the research on macronutrient ratios for body composition and performance shows a wide range of splits can work, provided total calories and protein are adequate. Treat the presets as reasonable, well-established starting points rather than a fixed prescription, and adjust based on how you feel, perform, and progress over several weeks.

Which Macro Split Preset Is Actually Right for You? — a closer look at what balanced, low-carb, high-protein, keto, and endurance each optimize for.
Fibermaxxing: How Much Fiber Is Too Much? — more on the 14g-per-1,000-kcal fiber target this calculator uses.
How to Build a Balanced Lunch Box for Kids — applying a macro split to a much smaller daily calorie target.

Frequently asked questions

What do the diet style presets actually change?

Only the ratio of calories assigned to carbohydrate, protein, and fat — never your total calorie target. Balanced is an even 40/30/30 split. Low-carb shifts toward fat (25/35/40). High-protein pushes protein up (35/40/25). Keto is a strict low-carb split (5/25/70). Endurance leans carb-heavy for people training for long-duration sport (55/20/25). None of them is inherently 'better' — they suit different goals and preferences.

Why does the calculator warn me about low protein sometimes?

It checks your protein grams per kilogram of bodyweight against evidence-based floors: 1.6–2.2g/kg if you train regularly, or a 0.8g/kg general minimum otherwise. A preset like keto, combined with a lower body weight, can sometimes land under that floor — the warning tells you so without silently changing your chosen split for you.

Why can't I set carb, protein, and fat to whatever I want?

You can — the custom sliders let you set any combination — but the three always have to total 100% of your calories, since they're percentages of the same number, not independent amounts. Moving one slider redistributes the other two proportionally so the total stays exact.

What is the fiber target based on?

A simple, widely used rule of 14 grams of fiber per 1,000 kcal consumed. It scales the target with your calorie intake rather than giving everyone the same fixed number, which would systematically overshoot for smaller calorie targets and undershoot for larger ones.

Why are protein and carbs 4 kcal per gram but fat is 9?

Different macronutrients have different energy densities. Protein and carbohydrate both yield about 4 kcal per gram when metabolised; fat yields about 9. That's roughly double, which is why fat-heavy diets pack more calories into less food volume.