Macros: Calories → Grams With the 4-4-9 Rule
Food & Nutrition · 5 min read · Last updated September 2026
The rule
Carb g = (calories × C%) ÷ 4
Fat g = (calories × F%) ÷ 9
Worked example — 2,400 kcal, 30% protein / 40% carbs / 30% fat: protein 2,400 × 0.30 ÷ 4 = 180 g; carbs 2,400 × 0.40 ÷ 4 = 240 g; fat 2,400 × 0.30 ÷ 9 = 80 g. Check: 180×4 + 240×4 + 80×9 = 720 + 960 + 720 = 2,400 ✓.
Common splits and what they emphasize
| Split (P/C/F) | 2,400 kcal → grams | Character |
|---|---|---|
| 30/40/30 | 180 / 240 / 80 | Balanced default |
| 35/20/45 | 210 / 120 / 120 | Lower-carb |
| 20/5/75 | 120 / 30 / 200 | Keto-style |
Sanity checks before trusting a split
Protein below ~1.2 g/kg of body weight under-supports muscle retention on a deficit; fat below ~0.5 g/kg can affect hormone function over long stretches; carbs fueling hard training below ~3 g/kg makes heavy sessions feel flat. If a fashionable split violates these bands for your body weight, treat it skeptically. Set your calorie target first (see the TDEE guide), then split it — the TDEE & Macro Calculator does both steps; Macro Split and Daily Protein Need cover the individual pieces.
Try the calculators
Worked example: TDEE and Macro Calculator at its default inputs
Open TDEE and Macro Calculator and press calculate without editing a field. What comes back is the table and result below, so the macro-calculator numbers here are checkable in one click.
| Input | Default |
|---|---|
| Weight (kg) | 70 |
| Height (cm) | 170 |
| Age | 30 |
| Sex (1=male, 0=female) | 1 |
| Activity Multiplier (1.2–1.9) | 1.55 |
| Protein % of Calories | 30 |
Result: TDEE: 2507 kcal
The steps behind that answer
- Step 1: BMR (Mifflin-St Jeor) = 1618
- Step 2: TDEE = BMR × activity = 1618 × 1.55 = 2507 kcal
- Step 3: Protein 30% → 188 g, fat 30% → 84 g, carbs fill the rest
- Cut 300–500 kcal for loss; add 200–300 for lean gain
Sensitivity: Weight (kg) from half to one-and-a-half times
Hold every other field still and move only weight (kg).
| Weight (kg) | Result |
|---|---|
| 35 | TDEE: 1965 kcal |
| 70 | TDEE: 2507 kcal |
| 105 | TDEE: 3050 kcal |
If the rows barely differ, weight (kg) is not your lever — change a different input. If they swing widely, get that number right before trusting the total.
Related guides
Calories set the size, macros set the composition
A macro split divides a calorie target into protein, carbohydrate and fat. It cannot fix a calorie target that is wrong for your goal: 40/30/30 of too many calories still gains fat, and the same split of too few still loses muscle.
Set protein from body weight first (roughly 1.6-2.2 g/kg for active people), then fat as a minimum (about 0.6-1 g/kg for hormones and absorption), and give the remainder to carbohydrate. That order keeps the essential parts covered.
Grams versus percentages
Percentages look tidy but scale badly: the same 30% protein is a different gram amount for a 1,600 and a 3,200 calorie plan. People with very different body sizes should not share a percentage split.
Fix protein in grams, then express the rest as percentages for convenience. The plan becomes both comparable and portable.
Adherence beats the perfect ratio
A split you can hold for months outperforms an optimal one you abandon in three weeks. That usually means fewer rules and more repeatable meals rather than precise percentages.
Track for a week to see what your current intake actually looks like before changing anything. Most people are surprised by fat or by liquid calories, not by protein.
Prepping two or three repeatable meals removes most of the daily decision-making. A plan built around food you actually cook is more likely to survive a busy week than an ideal split built around recipes you never make.
Frequently asked questions
How do I calculate macros from calories?
Assign percentages to protein, carbs and fat, then divide: protein and carb grams = (calories × share) ÷ 4; fat grams = (calories × share) ÷ 9. Example: 2,400 kcal at 30/40/30 → 180 g protein, 240 g carbs, 80 g fat.
What is the 4-4-9 rule?
The energy densities: 4 kcal per gram of protein, 4 per gram of carbohydrate, 9 per gram of fat. It is how nutrition labels convert grams to calories and how macro percentages become gram targets.
What macro split should I use?
Start from a balanced 30/40/30 and adjust one variable at a time against your training and appetite. Keep protein at 1.2–2.2 g/kg body weight and fat above 0.5 g/kg regardless of style.
Do macro grams or percentages matter more?
Percentages are the input; grams are the actionable output. Nobody weighs "30%" — you weigh 180 g of protein. Always convert the split into gram targets for your calorie level.
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