NUTRITION GUIDE
How do you choose optimal macros?
There is no single macro ratio that is optimal for everyone. A useful target is a starting estimate that fits your goal, food preferences, training, and health context—and that you can review and adjust.
What are macros?
Macronutrients are protein, carbohydrate, and fat. They contribute energy and have different roles in the diet. Calories summarize estimated energy; macros describe some of the food composition behind that number. Fiber and vitamins and minerals are tracked separately.
Start with a calorie estimate, not a promise
Equations such as Mifflin–St Jeor estimate resting energy expenditure from variables including age, height, weight, and sex. An activity factor can estimate total daily needs, but individual energy expenditure varies. Treat the result as a place to start, then consider your longer-term weight and training trends rather than reacting to one day.
Set protein with your context in mind
For people doing resistance training, research reviews discuss protein intakes in relation to body mass and training outcomes; they do not imply that one number fits every person or medical situation. The Morton et al. meta-analysis found diminishing average benefits around 1.6 g/kg/day in its studied population, with uncertainty around the estimate. Individual needs can differ, and kidney disease or other clinical needs call for professional advice.
Carbohydrate and fat do not have one required split
After choosing a reasonable energy and protein starting point, carbohydrate and fat can be balanced in ways that suit your diet, activity, and preferences while meeting applicable dietary guidance. A calculator’s split is an explicit arithmetic choice, not proof that the result is biologically optimal.
Use a calculator carefully
Speed Macros’s free calorie, macro, and micronutrient calculator estimates energy with Mifflin–St Jeor and uses a transparent goal-based allocation for macros. The tool runs in your browser. Review the assumptions and limitations before using any number.
This general adult guide and calculator are not intended for people under 18, pregnancy or breastfeeding, eating-disorder care, or medical nutrition therapy. Consult a registered dietitian or clinician for individualized needs.
Sources and review
- Mifflin et al. (1990), resting energy expenditure prediction equation
- Morton et al. (2018), protein supplementation and resistance training meta-analysis
- International Society of Sports Nutrition position stand on protein and exercise
Editorial review: September 20, 2026. This page is educational and has not been reviewed by a registered dietitian.