Calorie Calculator

1. Select your unit system. Imperial (pounds and inches) or Metric (kg and cm).
2. Enter your sex and age. Men and women have different BMR baselines. Age reduces BMR by roughly 1 to 2% per decade after 20.
3. Enter your height and current weight. Weigh yourself in the morning before eating for consistency.
4. Set your goal weight and timeframe. The calculator determines the exact daily calorie target needed to reach your goal in the time you choose. Be realistic: more than 1.5 lbs/week loss usually requires an aggressive deficit that is hard to sustain.
5. Choose your activity level honestly. Most people overestimate this. Sedentary means a desk job with no deliberate exercise. Moderately active means at least 3 real workout sessions per week.
6. Pick a BMR formula. Mifflin-St Jeor is the most accurate for most people. Katch-McArdle is better if you know your body fat percentage, since it uses lean mass instead of total weight.
7. Read your projection chart. The chart shows your expected weight over the full timeframe based on the calculated calorie target.

This calculator supports three BMR formulas. All are multiplied by an activity factor to estimate Total Daily Energy Expenditure (TDEE).

Mifflin-St Jeor (default, most accurate)

Validated in a 2005 study as the most accurate predictive equation for most adults, within 10% of measured metabolic rate.

Men:   BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

Harris-Benedict (revised 1984)

The original formula from 1919, revised in 1984. Slightly less accurate than Mifflin for most people but widely used clinically.

Men:   BMR = 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Women: BMR = 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)

Katch-McArdle (uses lean body mass)

The most accurate formula for lean or athletic individuals. Requires knowing your body fat percentage.

BMR = 370 + (21.6 × Lean Body Mass in kg)
Lean Body Mass = Total Weight × (1 − Body Fat %)

Activity Multipliers (Harris-Benedict factors)

Worked Example

30-year-old male, 5'10" (178 cm), 175 lbs (79.4 kg), moderately active, goal: 160 lbs in 12 weeks.

BMR = (10 × 79.4) + (6.25 × 178) − (5 × 30) + 5 = 1,762 cal
TDEE = 1,762 × 1.55 = 2,731 cal/day

Weight to lose: 15 lbs over 12 weeks = 1.25 lbs/week
Required deficit: 1.25 × 500 = 625 cal/day
Daily target: 2,731 − 625 = 2,106 cal/day

Knowing your TDEE is the starting line. The 500-calorie deficit rule (1 lb/week loss) works well as a general guide, but real fat loss is not perfectly linear. Weight fluctuates day to day due to water, sodium, and glycogen. Judge progress over 2 to 4 week averages, not daily readings.

How Aggressive Should Your Deficit Be?

Going below 1,200 calories (women) or 1,500 calories (men) without medical supervision risks muscle loss and metabolic slowdown.

Why Zig-Zag Calorie Cycling Works

Eating the exact same calories every day trains your metabolism to adapt to that intake. Cycling between higher and lower days keeps the same weekly total while preventing this adaptation. It also gives you flexibility: low calorie days on weekdays, higher intake on weekends when social meals are harder to control.

Calorie Targets for Muscle Building

For a lean bulk (muscle gain with minimal fat), add 200 to 300 calories above TDEE. Pair this with 0.7 to 1 gram of protein per pound of bodyweight and progressive resistance training. A larger surplus of 500+ builds muscle faster but adds more fat. Most intermediate lifters do better staying in the 200 to 300 range and adjusting every 4 to 6 weeks.

For more detail on macro breakdown alongside calories, see our macro calculator. To adjust for body composition, the TDEE calculator supports body fat percentage input for a more precise maintenance estimate.