How the keto calculator works
The goal of a keto diet is simple: eat few enough carbs to shift your body from burning sugar to burning fat, while getting enough protein to protect muscle and enough fat to feel good. This calculator turns that idea into real numbers for your body.
First it estimates your basal metabolic rate (BMR), the energy you burn at rest. If you leave body fat blank, it uses the Mifflin-St Jeor equation, the most accurate general formula for most people. If you enter a body fat percentage, it switches to the Katch-McArdle equation, which is based on lean body mass and tends to be more precise for lean or muscular people.
Next it multiplies your BMR by an activity factor to get your total daily energy expenditure (TDEE), the calories you actually burn in a day. The five activity levels run from sedentary (1.2) up to extra active (1.9). Be honest here, since most people overestimate how active they are.
From your TDEE the calculator applies your goal. Choose lose weight and it subtracts a deficit you control with a slider (5 to 30 percent). Choose gain muscle and it adds a surplus (5 to 15 percent). Choose maintain and it keeps you at your TDEE. That gives your target calories.
How your macros are set
Instead of forcing a rigid percentage split, the calculator sets your macros in the order that keeps you in ketosis:
- Net carbs come first, fixed by the carb slider (default 25 grams). Carbs supply 4 calories per gram.
- Protein comes next, based on your protein slider (0.6 to 1.0 grams per pound). It uses your lean mass when you enter body fat, otherwise your bodyweight. Protein supplies 4 calories per gram.
- Fat fills whatever calories are left, at 9 calories per gram. Fat is your lever: eat to your fat target when hungry, and pull back on fat first when you want to lose faster.
How to use the numbers
Treat your fat and protein targets as goals and your carb number as a ceiling. Hit protein most days, keep net carbs at or below the number shown, and use fat to fill the gap. You do not need to be perfect. Getting close, most days, is what drives results. If you are new to this, our 7 day keto meal plan shows what these numbers look like on an actual plate, and the keto food list makes shopping easy.
Not sure whether a food fits your carb ceiling? Read the label and run it through our net carbs calculator to see the net carbs per serving before it goes in your cart.
When to recalculate
Your numbers are a starting point, not a law. Track your weight and energy for two to three weeks, then adjust. If you are losing too slowly, increase the deficit or trim fat grams. If you feel drained or are losing muscle, add protein or ease the deficit. Recalculate whenever your weight moves by about 10 pounds or your training changes, because your maintenance calories fall as you get lighter.
Want to confirm you are actually in ketosis rather than guessing? A keto blood meter gives you a real reading, and our guide on how long it takes to get into ketosis sets expectations for the first week.