Macros & Intake
10 calculators
Intake calculators split a calorie figure into macronutrients, or work out the arithmetic behind a specific dietary quantity: protein per kilogram, fluid, fibre, alcohol, caffeine clearance.
The energy side rests on the Atwater factors — 4 kcal per gram for protein and carbohydrate, 9 for fat, 7 for alcohol. Those four numbers are what turn any macro split back into calories and vice versa.
- Calorie Deficit Planner Work backwards from a target date to the daily calorie deficit and intake the timeline implies.
- Macro Split Calculator Convert calorie percentages into daily protein, carb, and fat gram targets based on your TDEE.
- Meal Planner Build a day of meals from 300+ common foods and see calories and macros add up against the targets you set.
- Protein Intake Calculator Multiply body weight by grams-per-kilogram rate to estimate daily protein intake in grams.
- Alcohol Calories Calculator Estimate the caloric contribution of ethanol in alcoholic beverages using ABV and serving size.
- Caffeine Half-Life Calculator Estimate remaining caffeine in your system using exponential decay and a 5-hour half-life.
- Dietary Fiber Reference Calculator Restate the commonly cited 14 g per 1,000 kcal fiber guideline at any calorie intake.
- Water Intake Calculator Estimate daily water intake using body weight and activity level with clinical hydration guidelines.
- Carb Cycling Calculator Estimate weekly calorie distribution across high-, medium-, and low-carb training days.
- Meal Portion Scaling Calculator Scale recipe ingredient quantities proportionally when changing serving counts.
Splitting calories into grams
A macro split is a percentage allocation of a calorie total, converted to grams through the Atwater factors. At 2,000 kcal with 30% protein, the protein share is 600 kcal, which at 4 kcal per gram is 150 g. The same 600 kcal allocated to fat would be 67 g, because fat carries more than twice the energy per gram.
That asymmetry is why fat percentages look small in grams and carbohydrate percentages look large, and why comparing two diets by gram counts alone can be misleading unless the calorie totals match.
The deficit planner runs the chain in the other direction: it estimates resting metabolism through Mifflin-St Jeor, scales it by an activity factor to reach total daily expenditure, then divides a target weight change by the number of weeks to find the daily energy gap that arithmetic implies. The 7,700 kcal per kilogram figure it uses is the conventional energy density of body tissue.
The single-quantity calculators
Protein intake is expressed per kilogram of body mass because that is how the research literature reports it, with commonly cited ranges spanning roughly 1.2 to 2.2 g/kg depending on the population studied. Fibre uses a different convention entirely: 14 g per 1,000 kcal, which scales the figure with energy intake rather than body size.
Caffeine clearance follows first-order kinetics with a half-life commonly cited at around five hours, so a 200 mg dose leaves roughly 100 mg after five hours and 50 mg after ten. Alcohol energy uses the 7 kcal per gram factor applied to ethanol volume, which is why a drink's calorie content tracks its ABV and volume rather than its type.
Common questions
How do I convert macro percentages into grams?
Multiply the calorie total by the percentage, then divide by the energy density of that macronutrient: 4 kcal per gram for protein and carbohydrate, 9 for fat. At 2,000 kcal, a 30% protein share is 600 kcal, which is 150 g. The same percentage allocated to fat gives 67 g, because fat carries more than twice the energy per gram. This is what the Atwater factors describe, and every macro tool here applies them.
Why does the deficit planner use 7,700 kcal per kilogram?
It is the conventional figure for the energy density of body tissue, derived from the composition of adipose tissue and long used as a planning constant. It is an approximation: real tissue change includes water and lean mass in proportions that vary between people and over time, and expenditure itself changes as body mass falls. The planner states the arithmetic it performs rather than predicting an outcome.
How long does caffeine stay in your system?
Caffeine follows first-order elimination with a half-life commonly cited at around five hours in healthy adults, so each five-hour period removes half of what remains. A 200 mg dose is down to roughly 100 mg after five hours, 50 mg after ten and 25 mg after fifteen. That half-life varies substantially with liver enzyme activity, pregnancy, smoking status and certain medications, so the calculator uses the typical figure and shows the decay curve it produces.