How the protein calculator works
The calculator converts your weight to kilograms and multiplies it by a protein factor in grams per kilogram. The factors follow the International Society of Sports Nutrition position stand: roughly 0.8–1.2 g/kg for general health, 1.2–1.6 g/kg during weight loss, 1.6–2.0 g/kg when the goal is to preserve or build muscle while losing fat, and 1.8–2.2 g/kg for maximum muscle preservation in a sustained deficit. Higher activity levels add a small bump. The result is shown as a recommended target with a minimum and an optimal figure, then split across three or four meals, because spreading protein through the day is what the evidence supports for muscle protein synthesis.
Why protein matters more when you're eating less
When total food intake falls — through dieting, reduced appetite, or illness — the body draws on muscle as well as fat unless protein intake stays high and some resistance activity continues. Losing muscle lowers resting energy use and makes weight regain more likely. Hitting a protein target on low-hunger days usually means leading each meal with the protein portion and keeping convenient high-protein foods on hand: eggs, Greek yogurt, cottage cheese, fish, poultry, tofu, lentils, and protein powder if whole food is hard to face.
About the water and calorie calculators
The water calculator starts from a common rule of thumb (about half an ounce per pound of body weight), adjusts for climate and exercise, and adds a margin when you're eating less, since food normally supplies a meaningful share of daily fluid. The calorie calculator uses the Mifflin-St Jeor equation for resting metabolic rate, multiplies by an activity factor, and shows a moderate deficit range. All three are estimates to start from, not rules.