Macro Calculator (Protein, Carbs & Fat)
Turn a calorie target and your chosen protein/carb/fat split — including keto ratios — into grams per day.
In short
Turn a calorie target and your chosen protein/carb/fat split — including keto ratios — into grams per day.
Formula: grams = calories × share ÷ energy per gram, using general Atwater factors: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g.
What this calculator does
Turn a calorie target and your chosen protein/carb/fat split — including keto ratios — into grams per day. Formula, worked example, sources, FAQs and limitations included.
You enter daily calorie target, protein share, carbohydrate share and fat share, and the macro calculator (protein, carbs & fat) shows the answer along with the working, so you can check it or try other numbers.
The page shows the formula, a numeric worked example, and the assumptions that affect this health & fitness calculation.
Inputs and what they mean
- Daily calorie target
- — number value.
- Protein share
- — number value.
- Carbohydrate share
- — number value.
- Fat share
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Source: FAO Food and Nutrition Paper 77 (2003), Food energy — methods of analysis and conversion factors, general Atwater factors.
You choose the calorie target and the split; no diet ratio is preset. A ketogenic split is simply a low carbohydrate share you enter.
grams = calories × share ÷ energy per gram, using general Atwater factors: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g.
Inputs used: Daily calorie target, Protein share, Carbohydrate share, Fat share.
Worked example
2,000 kcal at 30/40/30
- Protein: 2000 × 0.30 ÷ 4 = 150 g.
- Carbohydrate: 2000 × 0.40 ÷ 4 = 200 g.
- Fat: 2000 × 0.30 ÷ 9 ≈ 66.67 g.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- General Atwater factors are averages; specific foods differ.
- Not medical nutrition therapy.
- For general fitness education only — not medical advice, diagnosis or a training prescription. Prediction equations are population estimates; speak with a qualified professional before changing exercise or diet, especially with a health condition.
- The result depends on the values you enter for this macro calculator (protein, carbs & fat); it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: FAO
Last reviewed:
Common questions
What split should I use?
The calculator does not choose one. Ratios depend on your goals and health; a registered dietitian can advise.
How do I calculate keto macros?
Enter your own low carbohydrate share (for example 5%) with protein and fat shares that total 100%.
Why does alcohol not appear?
Only protein, carbohydrate and fat are split. Alcohol (about 7 kcal/g) and fibre are outside this calculation.
How do I use the Macro Calculator (Protein, Carbs & Fat)?
Enter the required values for Daily calorie target, Protein share, Carbohydrate share, Fat share. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Macro Calculator (Protein, Carbs & Fat) use?
grams = calories × share ÷ energy per gram, using general Atwater factors: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Macro Calculator (Protein, Carbs & Fat) be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Sources
Method based on FAO.
Cite this page
Free Calculator. (2026, November 3). Macro Calculator (Protein, Carbs & Fat). https://freecalculator.tech/tools/macro-calculator
"Macro Calculator (Protein, Carbs & Fat)." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/macro-calculator.
Macro Calculator (Protein, Carbs & Fat) — Free Calculator, https://freecalculator.tech/tools/macro-calculator
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