BYTETOOLS

Macro Calculator

Turn a daily calorie target into grams of protein, carbohydrate and fat using preset or custom macro splits, with a per-meal breakdown and metric or imperial input.

2,000 kcal
Daily calories
200 g
Carbohydrate (40%)
150 g
Protein (30%)
67 g
Fat (30%)

Daily and per-meal breakdown

MacroShareCaloriesGrams/dayGrams/meal (3)
Carbohydrate (4 kcal/g)40%800200 g67 g
Protein (4 kcal/g)30%600150 g50 g
Fat (9 kcal/g)30%60067 g22 g

Grams are derived with the Atwater factors — 4 kcal/g for protein and carbohydrate, 9 kcal/g for fat. The arithmetic is exact, but the inputs are not: calorie targets carry roughly 10% prediction error and food labels are legally allowed to be off by up to 20%. Estimates for planning only, not nutritional or medical advice.

What is the Macro Calculator?

A macro calculator converts a daily calorie target into grams of protein, carbohydrate and fat using a chosen percentage split, at 4 calories per gram for protein and carbs and 9 calories per gram for fat.

  • Five presets plus a fully custom percentage split
  • Calorie target entered manually or computed from Mifflin-St Jeor
  • Grams and calories shown for every macronutrient
  • Per-meal breakdown for 2 to 6 meals a day
  • Metric and imperial body measurements
  • Runs entirely in your browser — no uploads, no account

How to use the Macro Calculator

  1. 1

    Enter a daily calorie target, or switch to calculating one from your stats.

  2. 2

    Choose a macro preset, or select Custom and set your own percentages.

  3. 3

    Check that a custom split adds up to 100 percent.

  4. 4

    Set how many meals you eat per day.

  5. 5

    Read the grams and calories for each macro, per day and per meal.

About the Macro Calculator

The ByteTools Macro Calculator turns a daily calorie number into grams of protein, carbohydrate and fat. Pick a preset split — balanced, high protein, low carb, ketogenic or endurance — or set your own percentages, and it converts using the standard Atwater values of 4 kcal per gram for protein and carbs and 9 kcal per gram for fat.

You can enter a calorie target directly or let the tool work one out from your sex, age, height, weight, activity level and goal using the Mifflin-St Jeor equation. Height and weight accept metric or imperial units, and a per-meal breakdown divides the day across the number of meals you actually eat.

All of it is computed in your browser with nothing uploaded or stored. These are estimates for planning only and not nutritional or medical advice — macro splits are a framework, not a prescription, and anyone with a medical condition should talk to a registered dietitian before restructuring their diet.

Frequently asked questions

How do I calculate my macros?

Multiply your daily calories by each macro's percentage, then divide by its calorie density — 4 for protein, 4 for carbohydrate and 9 for fat. On 2,000 calories with a 40/30/30 carb/protein/fat split that is 200 g carbs, 150 g protein and 67 g fat.

What is the best macro split for weight loss?

Total calories drive weight loss far more than the split does, but a higher protein share — roughly 30 to 40 percent of calories — helps preserve muscle and keeps you fuller in a deficit. Beyond that, the best split is the one you can actually stick to.

How accurate are macro calculators?

The conversion arithmetic is exact, but everything feeding into it is an estimate. The calorie target comes from a prediction equation with roughly 10% error, food labels are legally allowed to be off by up to 20%, and the 4/4/9 Atwater factors are population averages that ignore fibre and digestibility. Expect to adjust after a few weeks of real-world feedback.

How many grams of fat should I eat per day?

Most guidelines put fat between 20 and 35 percent of calories, which on 2,000 calories is roughly 44 to 78 grams. Going much below 20 percent for long periods can affect hormone production and the absorption of fat-soluble vitamins.

Do macros need to be exact every day?

No. Hitting your protein target consistently matters most; carbs and fat can move around between days with little consequence as long as weekly calories are where you want them. Chasing gram-perfect precision daily usually costs more in stress than it returns in results.

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