Calorie & body calculators
From baseline metabolism to deficit targets, the full set of body-composition tools, all using the same Mifflin-St Jeor foundation.
Most weight and nutrition calculators boil down to two equations: a baseline metabolic rate (BMR) and a multiplier for activity. Once you have those, every other number, calorie target, macros, deficit, is arithmetic on top.
Start with the baseline. The BMR calculator gives your at-rest calorie burn (the floor, what your body uses doing nothing). The TDEE calculator multiplies that by an activity factor to give your maintenance calories, what you burn on a typical day. The calorie calculator combines both and adds a goal adjustment (loss / maintain / gain).
For weight goals, the calorie deficit calculator translates a target loss rate into a daily deficit (1 lb/week ≈ 500 cal/day). The macro calculator splits that target into protein, carbs, and fat at common ratios (cutting, recomp, bulk).
For body composition, the BMI calculator and metric BMI use the standard NIH formula, a quick screening number, but it can't distinguish muscle from fat. The body fat calculator uses the US Navy method to estimate body fat percentage from circumferences. The ideal weight calculator gives the four classic clinical formulas (Devine, Robinson, Miller, Hamwi) for context.
For day-to-day tracking, the water intake calculator estimates daily fluid needs, and the target heart rate calculator gives the training zones (fat-burn, cardio, peak) for cardio sessions.
These are estimates, not prescriptions, useful for setting initial targets, then adjusting based on actual results over 2–4 weeks.
Baseline metabolism
Start here, what your body burns at rest and on a typical day.
- BMR Calculator Estimate your basal metabolic rate (BMR) using the Mifflin-St Jeor equation. Enter age, sex, height, and weight to see calories burned at rest.
- TDEE Calculator Calculate your Total Daily Energy Expenditure (TDEE) in metric units using the Mifflin-St Jeor BMR formula and your activity level. Get maintenance calories.
- Calorie Calculator Estimate your daily calorie needs (TDEE) based on age, sex, weight, height, and activity. Includes maintenance, weight-loss, and muscle-gain targets.
Weight goals
Translate a target loss/gain rate into daily calories and macros.
- Calorie Deficit Calculator Calculate your target calorie intake for weight loss. Subtract a daily deficit from your TDEE to see weekly and monthly fat-loss projections.
- Macro Calculator Split a daily calorie target into protein, carb, and fat grams using your chosen macro ratio. Useful for IIFYM, cutting, bulking, and meal prep planning.
Body composition
BMI, body fat, and ideal weight benchmarks.
- BMI Calculator Calculate your BMI (body mass index) from height and weight. Includes the WHO category bands, what BMI actually measures, and where it breaks down.
- BMI Calculator (Metric) Calculate BMI from height in centimeters and weight in kilograms. Uses the metric formula kg ÷ m² with the WHO category bands and interpretation notes.
- Body Fat Calculator Estimate body fat percentage using the US Navy circumference method. Enter sex, height, neck, waist, and (for women) hip measurements for an estimate.
- Ideal Weight Calculator Estimate your ideal body weight using the Devine formula. Enter height and sex to see a target weight range used by clinicians for medication dosing.
Day-to-day
Hydration and heart-rate targets for ongoing tracking.
- Water Intake Calculator Estimate your daily water needs based on body weight and exercise. Enter your weight in pounds and exercise minutes for a baseline ounce-per-day estimate.
- Target Heart Rate Calculator Calculate your max heart rate and training zones from age. See your fat-burn (50-70%) and cardio (70-85%) zones in beats per minute for safer cardio.