Updated
Meal Portion Calculator for Coaches
Enter a food's protein, carbohydrate and fat per 100 g. Choose a protein or carbohydrate target to calculate the portion weight. Use your own food label; the defaults are fictional label values for an arithmetic example.
Estimates for planning, not medical advice. Choose targets within your professional scope.
Use the calculator
Estimates for planning, not medical advice. Choose targets within your professional scope. Inputs stay in this browser and are not saved or sent to an AI service.
Method and assumptions
Portion weight (g) = target macro grams ÷ selected macro grams per 100 g × 100. Each macro in the portion = its label value per 100 g × portion weight ÷ 100. This scales one food to one target; it does not balance a whole meal or prescribe a target.
Fictional example: a label with 20 g protein, 10 g carbohydrate and 5 g fat per 100 g. A 30 g protein target gives 150 g of food, containing 30 g protein, 15 g carbohydrate and 7.5 g fat. These are invented example values, not nutrition data for a real food.
Use the same basis as the label: a raw-food label needs raw weight; a cooked-food label needs cooked weight. This tool does not convert raw food to cooked food. If a label gives values per serving, first divide each value by the serving weight in grams and multiply by 100. Do not add sugars or fibre to the carbohydrate input again.
Each label value must be between 0 and 100 g, and the three values must total no more than 100 g per 100 g. Check the label if rounded values exceed that total. A positive target cannot use a food with zero of the chosen nutrient. A zero target returns a zero portion; it is not a meal recommendation.
Ounces are weight, not fluid ounces: 1 oz = 28.349523125 g. Results display two decimal places while calculations keep full precision. Label rounding and weighing precision limit accuracy. No food database or calorie estimate is used.
Worked example with default inputs
- Protein per 100 g of food (g)
- 20
- Carbohydrate per 100 g of food (g)
- 10
- Fat per 100 g of food (g)
- 5
- Macro to calculate the portion from
- protein
- Target amount of the selected macro (g)
- 30
Portion and macros are calculated from your label values. Match raw or cooked weight to the label. Display values are rounded to two decimals; very small amounts may display as 0.
| Portion (g) | Portion (oz) | Protein (g) | Carbohydrate (g) | Fat (g) |
|---|---|---|---|---|
| 150 | 5.29 | 30 | 15 | 7.5 |
Related resources
Frequently asked questions
How do I calculate a food portion from a protein target?
Divide your target protein grams by the label's protein grams per 100 g, then multiply by 100. The result is food weight in grams. The calculator also shows the carbohydrate and fat in that portion.
Can I calculate a carbohydrate portion instead?
Yes. Select carbohydrate and enter the carbohydrate target in grams. The portion is calculated from the label's carbohydrate value, while protein and fat are scaled with it.
Should I weigh food raw or cooked?
Match the label. Use raw weight for values given for raw food, and cooked weight for values given for cooked food. The calculator does not account for cooking-related weight changes.
What if the food contains none of my target macro?
A food with zero of the chosen macro cannot supply a positive target. Choose another food. A target of zero gives a zero portion, including when the label value is zero.
Does this tell me how much a client should eat?
No. You choose the target. This is arithmetic for meal planning, not a nutrition prescription. Review the full meal, the client's needs and your professional scope before using the result.