Macro Calculator

Take your daily calorie target and split it into protein, carbs, and fat — in grams you can actually measure. Start from a preset, or dial in your own percentages.

Why it matters: Calories decide whether you lose or gain weight, but macros decide whether it's fat, muscle, or water. Hitting your protein target is the single biggest lever for keeping muscle while cutting.

Set your targets

Daily calories (kcal)

Tip: get this from our Calorie Calculator — it carries over automatically.

Split preset

Protein %

Fat %

Carbs %

Body weight (optional — for protein-per-kg)

Your daily macros

1800 kcal

Balanced split (30 / 30 / 40)

Protein Carbs Fat

Protein—

Carbohydrates—

Fat—

Protein per kg of body weight—

← Calorie calculator Build a grocery list → Check your protein target →

Link to or embed this calculator

Reference it in a blog post, or paste this iframe on your own site (it includes a credit link back to Prep & Lose).

Macro targets are estimates for general nutrition planning, not medical advice. Very low-carb or very high-protein diets may not suit everyone — check with a healthcare professional.

What "Macros" Are — and Why the Split Matters

"Calories in vs. calories out" decides whether you lose or gain weight, but the breakdown of those calories decides what you lose or gain — fat, muscle, or water. That breakdown is your macronutrients: protein, carbohydrates, and fat.

Each gram carries a fixed energy value:

Protein — 4 kcal/g
Carbohydrates — 4 kcal/g
Fat — 9 kcal/g (more than double, which is why high-fat foods are so calorie-dense)

Why protein comes first

If you only control calories, some of the weight you lose will be muscle. Prioritizing protein (roughly 1.6–2.2 g per kg of body weight) flips that: it preserves lean mass, keeps you full longer, and costs more energy to digest. That is why the High-Protein preset leans hard on protein, and why the calculator shows your "protein per kg" figure so you can sanity-check it.

Which preset should you pick?

Balanced (30/30/40) — a flexible default that works for most people.
High-Protein (40/30/30) — best for fat loss and retaining muscle.
Low-Carb (35/40/25) — fewer carbs, more fat; good if you feel better cutting starches.
Keto (25/70/5) — very low carb, very high fat; restrictive, so check with a professional first.
Custom — set your own percentages; they must total 100%.

Hit the week, not every meal

Don't aim to nail your macros at every single meal — average them across the week. Weigh yourself once a week at the same time, and if the trend stalls for two weeks, nudge protein or total calories rather than overhauling the whole plan.

From grams to grocery cart

Once you have your daily grams, the Grocery List Generator turns them into a real shopping list scaled to your target weight and household. And if you started from the Calorie Calculator, your numbers flow through automatically — no retyping.