A macro calculator with a clear method
Macros are protein, carbohydrate and fat: the nutrients that provide most dietary energy. Protein and carbohydrate each provide about four kcal per gram, while fat provides about nine. A useful plan accounts for all three, alongside food quality and a routine you can sustain.
This calculator implements the worked approach in Dr Richie Kirwan’s Heracles course, Optimizing Your Nutrition. It starts with energy needs, sets protein and fat in grams, then allocates the remaining calories to carbohydrate. It does not start with a fixed percentage split for everyone.
1. Estimate energy and choose your goal
We use the rounded revised Harris–Benedict resting energy equations and the activity factors explained in the TDEE calculator. Maintenance uses that estimate. Fat loss subtracts your selected 300–500 kcal deficit. Muscle gain adds a modest 200 kcal, following the course’s worked example.
2. Choose the nutrition reference weight
The default uses the lower of your current body weight and the weight at BMI 25 for your height. That follows the course example for avoiding oversized macro targets at higher body weights. It is a planning reference, not a diagnosis of your ideal weight. The result shows the number used, and you can choose current body weight instead if appropriate, for example with substantial muscle mass.
3. Set protein and dietary fat
The starting choices are 2 g of protein and 1 g of fat per kilogram of reference weight, matching the worked course example. You can adjust protein from 1.6 to 2.2 g/kg and fat from 0.8 to 1.2 g/kg. These are planning options; there is no requirement to choose the highest protein setting or the lowest fat setting.
Fat (g) = reference kg × fat factor
Carbohydrate (g) = [daily kcal − (protein g × 4) − (fat g × 9)] ÷ 4
4. Put your numbers into meals
Use the per-meal protein figure as a guide, then add carbohydrate and fat sources you enjoy. Include fruit, vegetables and fibre-rich foods. Fish, eggs, dairy, beans, lentils, tofu and mycoprotein such as Quorn can all help build varied meals.
As Richie’s course explains, consistency is more useful than chasing perfect tracking. Plan a few reliable meals, compare longer-term trends, and adapt as your needs change. The targets are starting estimates, not a personalised prescription or a promise of changes to testosterone.
Worked example
For a 35-year-old man, 95 kg and 175 cm, with a 1.4 activity factor, estimated maintenance is about 2,803 kcal. Choosing muscle gain adds 200 kcal. The unrounded reference weight is 76.56 kg, giving about 153 g protein, 77 g fat and 425 g carbohydrate at the default settings. Small differences from the course example reflect when rounding is applied.
Questions about this calculator
How does this use Richie’s course?
It follows the course’s worked approach to energy needs, reference weight, protein and fat, then assigns the remaining calories to carbohydrate. Use your own longer-term progress to refine the starting estimates.
Why not use a standard 40/30/30 split?
The course approach sets protein and fat relative to a reference body weight, then uses the remaining calories for carbohydrate. This makes the assumptions visible and lets the result change with your goal.
Can I lose fat and build muscle at the same time?
Body recomposition can occur, especially with appropriate resistance training, protein and recovery. A calculator cannot predict it. Choose the goal that best reflects your current priority and review your progress.
Do I need to hit every macro exactly?
No. Use these as starting targets. A sustainable routine, overall intake, food quality and longer-term progress are more useful than perfect daily numbers.
Method and sources
Nutrition principles adapted from Dr Richie Kirwan’s Heracles course, Optimizing Your Nutrition, Modules 1 and 3. Calculator implementation and explanations by Heracles.