Calorie Needs Formula

Health Formula • Published on July 30, 2026 • Last updated August 09, 2026

Mathematical Equation

$$\begin{aligned} BMR &= 10W + 6.25H - 5A + s \\ \text{Target Calories} &= (BMR \times \text{Activity Multiplier}) + \text{Goal Adjustment} \end{aligned}$$

Variable Definitions

W, H, A, s

Weight (kg), Height (cm), Age (years), and gender constant (+5 male, −161 female) — same Mifflin-St Jeor BMR inputs as the TDEE formula

Goal Adjustment

Calorie offset applied to TDEE based on fitness goal: mild loss −250, loss −500, extreme loss −1000, maintain 0, mild gain +250, gain +500

Detailed Explanation

In-Depth Guide

This formula extends the Mifflin-St Jeor TDEE calculation one step further by applying a calorie surplus or deficit based on a specific weight goal, producing a single daily calorie target. It relies on the widely-used approximation that roughly 500 kcal of daily deficit or surplus corresponds to about 0.5 kg (1 lb) of body weight change per week.

How to Calculate: Step-by-Step

1. Calculate BMR using the Mifflin-St Jeor equation from weight, height, age, and gender. 2. Multiply by an activity multiplier to get maintenance-level TDEE. 3. Choose a fitness goal (mild loss, loss, extreme loss, maintain, mild gain, or gain) and apply its corresponding calorie adjustment. 4. Add the adjustment to TDEE to get the daily Target Calories. 5. The result is floored at a safety minimum (1,500 kcal for men, 1,200 kcal for women) to avoid unsafely low targets.

Worked Calculation Example

Female, Weight = 65 kg, Height = 162 cm, Age = 28, Lightly Active (multiplier 1.375), Goal = Loss (−500 kcal): - BMR = 10×65 + 6.25×162 − 5×28 − 161 = 650 + 1,012.5 − 140 − 161 = 1,361.5 kcal - TDEE = 1,361.5 × 1.375 ≈ 1,872 kcal - Target Calories = 1,872 − 500 = 1,372 kcal → floored up to the 1,200 kcal safety minimum is not needed here since 1,372 > 1,200

Common Use Cases

  • Setting a daily calorie target for a specific weight loss or gain goal
  • Projecting weekly, monthly, and 3-month weight change at a given calorie target
  • Building a diet plan calorie baseline before applying a macro split

Frequently Asked Questions

It's a useful approximation but not perfectly precise — actual weight change also depends on changes in metabolic rate, water retention, and body composition, so real-world results often deviate somewhat from the simple linear prediction.

Calorie targets below roughly 1,200-1,500 kcal/day (depending on gender) risk inadequate nutrition, muscle loss, and metabolic slowdown, so the calculator caps the minimum recommended target regardless of how aggressive the deficit requested is.

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