A keto macro calculator turns your body and your goal into three daily numbers: how many grams of fat, protein, and carbs to eat. It starts by estimating the calories you burn in a day, then splits those calories the keto way, with carbs kept low, protein set to protect muscle, and fat filling the rest.
The estimate runs on the Mifflin-St Jeor equation, the formula dietitians reach for first, adjusted for how active you are and whether you want to lose, maintain, or gain. Carbs are capped where ketosis lives, around 20 to 25 grams of net carbs a day, and protein is anchored to your body weight rather than a flat percentage.
This calculator gives general estimates for education only. It is not medical, nutritional, or healthcare advice. Talk to a doctor or registered dietitian before starting keto, especially if you are pregnant or breastfeeding, have diabetes, kidney, liver, or heart conditions, take medication, or have a history of disordered eating. Not intended for anyone under 18.
How it works
The calculator runs four steps. First it estimates your basal metabolic rate (BMR), the calories you would burn at rest, from your sex, weight, height, and age. Second it multiplies that by an activity factor to get your total daily energy expenditure (TDEE). Third it adjusts for your goal: a 20 percent cut to lose, no change to maintain, or a 10 percent bump to gain. Fourth it splits the result into keto macros.
For the split, carbs are fixed at your chosen cap, protein is set from your body weight to hold onto muscle, and fat takes every calorie left over, since fat is the fuel keto runs on. That is why fat is the biggest number: it is the remainder, not a target you chase.
Frequently asked questions
How accurate is this calculator?
It is a solid estimate, not a measurement. Mifflin-St Jeor is among the most accurate prediction formulas for resting metabolism, but real burn varies with muscle, genetics, and movement. Use the numbers as a starting point, then adjust after two to three weeks based on what the scale and mirror do.
Why is fat the biggest number?
Because on keto fat is the fuel, and here it is the remainder. Once carbs are capped and protein is set to protect muscle, every remaining calorie goes to fat.
Why anchor protein to body weight?
Because protein need scales with your body, not your calorie total. Anchoring it to weight, around 0.8 grams per pound, keeps protein high enough to hold muscle while you lose fat.
Should I eat 20 or 25 grams of carbs?
Most people stay in ketosis at or under 25 grams of net carbs, and many use 20 to be safe. Start at 25, and if ketosis is hard to reach, drop to 20.
What activity level should I pick?
Be honest and pick low. Most people overestimate. If you sit most of the day and work out a few times a week, that is light, not very active. Choosing too high inflates your calories and stalls fat loss.