💪 HEALTH & FITNESS

IIFYM Macro Split Calculator

Q: What does IIFYM mean?

IIFYM stands for If It Fits Your Macros, a flexible dieting approach where you hit daily protein, carb and fat targets rather than following a fixed meal plan or food list.

Goal-based daily protein, carb and fat targets built from your TDEE — not a flat ratio. Tell us your goal, we calculate your calories first, then split them.

🎯IIFYM Calculator

"If It Fits Your Macros" — set your goal and get a personalized daily gram target for protein, carbs and fat.

Units

Sex

Weight (kg)

Height (cm)

Age

Activity Level

Goal

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Daily Calorie Target

What Makes This Different From a Macro Ratio Calculator

✓ BMR formula (Mifflin-St Jeor) and macro ranges cross-checked against standard sports-nutrition references — last checked June 2026.

Most "macro calculators" start with a fixed ratio — say 40% carbs, 30% protein, 30% fat — and apply it to whatever calorie number you type in. IIFYM ("If It Fits Your Macros") works the other way around: it calculates your calorie target first, from your actual stats and goal, then builds protein, carb and fat targets around that number using evidence-based gram-per-kilogram ranges rather than an arbitrary percentage split.

The process has three steps. First, your BMR (Basal Metabolic Rate) is estimated using the Mifflin-St Jeor equation, the most widely used formula in modern sports nutrition — repeatedly validated as more accurate than the older Harris-Benedict equation across non-obese and obese adults alike. Second, BMR is multiplied by an activity factor to get your TDEE (Total Daily Energy Expenditure) — your maintenance calories. Third, your goal shifts that number up or down: roughly 15-25% below TDEE for fat loss, or 10-20% above for muscle gain, with maintenance staying at TDEE itself.

How Macros Are Split

Goal	Protein target	Fat target	Carbs
Lose Fat	2.2g per kg bodyweight	25% of calories	Remainder
Maintain	1.8g per kg bodyweight	25% of calories	Remainder
Build Muscle	1.6g per kg bodyweight	25% of calories	Remainder

← Swipe to see all columns

Protein is set highest during a cut — it's the macro most responsible for preserving muscle in a calorie deficit — and can ease off slightly during a bulk where extra calories already support muscle retention. Fat is held at a steady 25% of total calories across all goals to protect hormone production and nutrient absorption, and carbohydrates fill whatever calories remain, since they're the most flexible macro for performance and daily energy.

Worked Example

Female, 65kg, 165cm, 28, Moderate Activity, Cutting

BMR = (10 × 65) + (6.25 × 165) − (5 × 28) − 161 = 1,332 kcal
TDEE = 1,332 × 1.55 = 2,065 kcal
Cut target = 2,065 × 0.80 = 1,652 kcal
Protein = 65kg × 2.2g = 143g (572 kcal)
Fat = 1,652 × 0.25 = 413 kcal ÷ 9 = 46g
Carbs = (1,652 − 572 − 413) ÷ 4 = 167g

Daily target: 1,652 kcal — 143g protein, 167g carbs, 46g fat.

These are evidence-informed starting points, not medical prescriptions — individual response varies, and anyone with a diagnosed eating disorder, pregnancy, or a medical condition affecting metabolism should work with a doctor or accredited dietitian rather than a calculator. For a closer look at how the equation was validated against other BMR formulas, see this nutrition-professional breakdown. Track your weight trend over 2-3 weeks and adjust calories by roughly 5-10% if progress stalls, using our Calorie Calculator as a quick recheck.

Frequently Asked Questions

What does IIFYM mean?+

IIFYM stands for "If It Fits Your Macros" — a flexible dieting approach where you hit daily protein, carb and fat targets rather than following a fixed meal plan or food list.

How is this different from a regular macro calculator?+

A regular macro ratio calculator applies a fixed percentage split to a calorie number you provide. This tool calculates your calorie target first from your BMR, activity level and goal, then derives gram-based macro targets from that number using goal-specific protein and fat guidelines.

How much protein do I need to lose fat without losing muscle?+

Around 2.0-2.2 grams of protein per kilogram of bodyweight is a commonly cited target for preserving muscle during a calorie deficit, which is higher than typical maintenance recommendations.

Why is fat kept at 25% across every goal?+

Dietary fat below roughly 20% of calories can affect hormone production over time. Holding it at a steady 25% protects that baseline while leaving protein and carbs to do the heavy lifting for each specific goal.

How often should I recalculate my macros?+

Recalculate whenever your weight changes by more than a few kilograms, your activity level shifts significantly, or your weight trend stalls for 2-3 weeks despite consistent tracking.