# IIFYM Calculator (If It Fits Your Macros)

URL: https://speedycalculator.com/calculators/health/iifym/
Last updated: 2026-10-30

> The IIFYM calculator builds a flexible-dieting macro plan: it estimates your TDEE, adjusts it for your goal, sets protein and fat per kilogram of body weight and fills the remaining calories with carbohydrates.

## Inputs

- Sex
- Age (years)
- Weight (kg, lb, st, g)
- Height (cm, in, m, ft, mm)
- Activity level
- Goal
- Protein (g per kg)
- Fat (g per kg)

## Results

- TDEE
- Target calories
- Protein
- Fat
- Carbohydrate
- Carbs as % of calories

## Formula

```
Target calories = TDEE × (1 + goal adjustment)
Protein g = weight × protein g/kg
Fat g = weight × fat g/kg
Carbs g = (target − protein × 4 − fat × 9) ÷ 4
```

## Explanation

"If it fits your macros" means any food can fit your diet as long as you hit your daily protein, carbohydrate and fat targets. Setting protein and fat first by body weight, then filling the rest with carbohydrate, is the approach used by most coaches.

### How to use the IIFYM Calculator

- **Sex**
- **Age**
- **Weight**
- **Height**
- **Activity level**
- **Goal**
- **Protein**
- **Fat**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter your details, activity level and goal, then the protein and fat you want per kilogram. The calculator works out the calories and macro grams.

### Inputs explained

FieldWhat to enterSexChoose one: Male, FemaleAgeIn yearsWeightUnits: kg, lb, st, gHeightUnits: cm, in, m, ft, mmActivity levelChoose one: Basal metabolic rate (no activity), Sedentary – little or no exercise, Light – exercise 1–3 times a week, Moderate – exercise 4–5 times a week …GoalChoose one: Lose fat (−20%), Lose slowly (−10%), Maintain, Lean bulk (+10%)ProteinIn g per kgFatIn g per kg

### What each result means

- **Target calories** = [TDEE]×(1 + [Goal]÷100)
- **Protein** = [Weight]×[Protein]
- **Fat** = [Weight]×[Fat]
- **Carbohydrate** = max(([Target calories] - [Protein]×4 - [Fat]×9)÷4, 0)
- **Carbs as % of calories** = [Carbohydrate]×4÷[Target calories]×100

### Example values

How the main result changes when **Age** changes and everything else stays at the example values above:

Age (years)Target calories (kcal/day)152,62622.52,571302,51637.52,461452,406602,296
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Sex: Male; Age: 30 years; Weight: 75 kg; Height: 178 cm; Activity level: Moderate – exercise 4–5 times a week; Goal: Maintain; Protein: 2 g per kg; Fat: 0.9 g per kg.

Results — TDEE = 2,516 kcal/day; **Target calories = 2,516 kcal/day**; Protein = 150 g/day; Fat = 68 g/day; Carbohydrate = 327 g/day; Carbs as % of calories = 52 %.

## Key terms

- **IIFYM**: If it fits your macros: flexible dieting based on macro targets.

## FAQ

**Can I eat anything on IIFYM?**
In principle, but most people feel and perform better when most of their food is minimally processed.

**Why set protein by body weight?**
Protein needs scale with body size and muscle, not with calories.

**What if carbs come out very low?**
Lower your fat per kg or reduce the deficit.


## Sources

- [Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990](https://pubmed.ncbi.nlm.nih.gov/2305711/)
- [Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr, 1984](https://pubmed.ncbi.nlm.nih.gov/6741850/)
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy and Human Performance
- [Dietary Guidelines for Americans 2020–2025](https://www.dietaryguidelines.gov/)