The short answer
A macro calculator estimates how many calories you eat a day and how they split into protein, carbohydrates and fat. This one estimates your resting energy with the Mifflin-St Jeor equation, multiplies it by an activity factor, adjusts the result for your goal, sets protein at 1.6 to 2.0 grams per kilogram of bodyweight (inside the 1.4 to 2 g/kg range from the ISSN position stand), puts 25% of calories in fat and gives the rest to carbohydrates. It runs in your browser and stores nothing.
Give every client their targets in their own portal
Work out the numbers here, then set them as your client's daily calorie and macro targets in RungGym. Your client logs meals against them on their phone, by searching a food database or typing a barcode. No app to install and no account to create. You open their food log before the next session instead of asking for screenshots.
How the numbers are calculated
1. Resting energy (BMR)
The Mifflin-St Jeor equation, with weight in kilograms, height in centimetres and age in years. It is defined separately for men and women, which is why the form asks for the sex used in the formula.
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
Women: BMR = 10 × weight + 6.25 × height − 5 × age − 1612. Maintenance calories
BMR multiplied by an activity factor, the conventional way to estimate total daily energy expenditure.
| Activity level | Factor |
|---|---|
| Sedentary: desk job, little or no exercise | 1.2 |
| Light: exercise 1 to 3 days a week | 1.375 |
| Moderate: exercise 3 to 5 days a week | 1.55 |
| Very active: hard exercise 6 to 7 days a week | 1.725 |
| Extra active: hard exercise plus a physical job | 1.9 |
3. Goal adjustment
A percentage added to or taken from maintenance. These percentages are common rules of thumb, not figures from the ISSN position stand. The calories are never set below your BMR.
4. Protein, fat and carbohydrates
The ISSN position stand on protein and exercise names 1.4 to 2 g per kg of bodyweight per day as sufficient for most people who exercise. The calculator picks a value inside that range for your goal. Fat takes 25% of calories, inside the 20 to 35% range that the US Institute of Medicine sets for adults. Carbohydrates fill the remaining calories.
| Goal | Protein (g per kg) |
|---|---|
| Lose weight (20% below maintenance) | 2 |
| Lose weight slowly (10% below maintenance) | 1.8 |
| Maintain weight | 1.6 |
| Gain weight (10% above maintenance) | 1.8 |
Protein (g) = g per kg × weight (kg)
Fat (g) = calories × 0.25 ÷ 9
Carbs (g) = (calories − protein × 4 − fat × 9) ÷ 4Limits of an estimate
- It is a prediction for healthy adults from 18 to 100, not a measurement.
- The ISSN range is for people who exercise. The general recommended intake for adults who do not exercise is 0.8 g per kg.
- Higher protein intakes may help lean people who strength train keep muscle in a deficit. The ISSN suggests this on lean body mass, which this form does not ask for.
- Not for anyone under 18, who is pregnant, has a medical condition or has had an eating disorder without guidance from a physician or dietitian.
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi:10.1093/ajcn/51.2.241 (opens in a new tab)
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. doi:10.1186/s12970-017-0177-8 (opens in a new tab)
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005 (acceptable macronutrient distribution ranges, and the 0.8 g/kg protein recommendation).
Frequently asked questions
How are macros calculated?
In four steps. Resting energy (BMR) comes from the Mifflin-St Jeor equation. It is multiplied by an activity factor from 1.2 to 1.9 to estimate maintenance calories, then raised or lowered for your goal. Protein is set per kilogram of bodyweight, fat takes 25% of the calories, and carbohydrates fill what is left, at 4 kcal per gram for protein and carbohydrates and 9 kcal per gram for fat.
How much protein do I need per kg of bodyweight?
The International Society of Sports Nutrition position stand on protein and exercise says 1.4 to 2.0 grams per kilogram per day is enough for most people who exercise. This calculator picks 1.6 g/kg to maintain, 1.8 g/kg to gain or lose slowly, and 2.0 g/kg when you eat in a deficit. The general recommended intake for adults who do not exercise is lower, at 0.8 g/kg.
How accurate is the Mifflin-St Jeor equation?
It is widely used and was found to predict resting energy more reliably than the other common equations in a 2005 review of healthy adults, but individuals still differ from the prediction. Treat the result as a starting point: follow your weight and how you feel for two to three weeks, then adjust the calories up or down.
Can I use the numbers for my clients?
Yes, as a starting point that you adjust from their check-ins. This is a general estimate for healthy adults. It is not suitable on its own for clients who are pregnant, under 18, have a medical condition or a history of disordered eating, who should work with their physician or a dietitian.
Is anything I type stored or sent?
No. The calculation runs in your browser. There is no account and nothing you enter is sent to a server or saved.
This calculator gives general estimates and is not medical advice. See also all free tools, online coach software and health coach software.