What to eat today, and why it is that number and not a rounder one.
If you gave a body fat percentage, the calculator uses Katch McArdle, which runs off lean mass: 370 + 21.6 × lean kg. Two people at the same weight with different amounts of muscle do not burn the same at rest, and this is the only common formula that knows that.
If you did not, it falls back to Mifflin St Jeor, the most accurate of the weight based equations: 10 × kg + 6.25 × cm − 5 × age, then +5 for men and −161 for women.
Your resting rate is multiplied by a factor for how much you move during a normal day: 1.20 seated, 1.30 on your feet, 1.45 physically active work, 1.60 heavy labor. That factor also covers the energy spent digesting food, which runs around 10% of intake.
These are deliberately lower than the multipliers you have seen elsewhere, because elsewhere they are doing two jobs at once. Here training is counted separately, so the multiplier only has to cover the rest of your life.
Each activity has a MET value, a measure of how hard it is relative to sitting still. A session costs (MET − 1) × 3.5 × kg ÷ 200 × minutes, and the weekly total is spread across seven days. Every slot you fill gets its own band in the ledger bar above.
The − 1 matters and almost nobody does it. A raw MET figure includes the energy you would have burned anyway just being alive during that hour, which your resting rate already counted. Subtracting it stops the same calories being counted twice. It makes the training numbers here look lower than other calculators. Other calculators are wrong.
Cut hard is 25% under maintenance, cut is 15% under, build is 10% over, build fast is 20% over. Percentages rather than a flat 500 calories, because 500 calories is a rounding error to a 250 lb strongman and a crash diet for a 110 lb runner. In the bar above it is the only thing drawn in orange, because it is the only thing you chose.
There is a hard floor. The target will not drop below 1.1 × your resting rate, and never below 1,500 calories for men or 1,200 for women. If the floor catches your inputs the stage says floor applied rather than quietly handing you an unsafe number.
Protein first. Set against lean mass, not scale weight, at 2.2 g per kg of lean mass, rising to 2.6 g in an aggressive cut where the job is holding onto muscle while the calories are low. Without a body fat figure it falls back to bodyweight at a lower rate, and it is capped at 40% of total calories.
Then fat, with a floor. Balanced puts fat at 30% of calories, performance at 22%, lower carb sets net carbs near 50 g and lets fat take the rest. In every case fat is held at or above 0.6 g per kg of bodyweight, because below that hormone production starts to suffer and no diet is worth that.
Carbs get what is left. They are the lever, not the constraint. That is also why the training day and rest day split moves carbs only: protein and fat stay where they are all week.
Every equation here is a population average applied to one person. Real world variation between two people with identical inputs runs to several hundred calories a day. The honest use of this tool is as a starting point you then correct: hold the number for two full weeks, track your weight every morning, and adjust by 100 to 150 calories based on what actually happened.
The rate of change shown on the stage uses the standard 3,500 calories per pound figure. It is reasonable for the first month and increasingly optimistic after that, because your body adapts to a lower intake. Treat it as a direction, not a schedule.
Not medical advice. This is an estimate produced by published equations, not a prescription. If you are pregnant or breastfeeding, managing diabetes, kidney or heart conditions, an eating disorder, or taking medication that affects appetite or metabolism, work with a registered dietitian or your physician before changing your intake. Anyone under 18 should not be running a calorie deficit off a web page.