Weight Loss Calculator: Personalized Plan for Healthy, Sustainable Results

How to use the tool

1. Fill your details. Example 1: Age 29, Female, 5 ft 6 in, 158 lb, Moderately active, lose 12 lb, 14 weeks. Example 2: Age 52, Male, 172 cm, 78 kg, Sedentary, lose 6 kg, timeframe blank.
2. Press “Calculate”. The tool returns BMI, BMR, TDEE, suggested calories, macros, and a weekly-weight chart.
3. Apply the numbers. Plan meals around the calorie and macro targets; review progress each week.

Key formulas

• BMI $$rac{\text{weight (kg)}}{(\text{height (m)})^{2}}$$
• Mifflin-St Jeor BMR Male: $$10w+6.25h-5a+5$$ Female: $$10w+6.25h-5a-161$$ where w=kg, h=cm, a=years.
• TDEE $$\text{BMR}\times\text{Activity Factor}$$
• Daily calories for goal $$\text{TDEE}-rac{\text{Goal Loss (kg)}\times7700}{\text{Days}}$$
• Macros 30 % protein, 40 % carbs, 30 % fat → Protein g = $$rac{0.30\times\text{Calories}}{4}$$ Carbs g = $$rac{0.40\times\text{Calories}}{4}$$ Fat g = $$rac{0.30\times\text{Calories}}{9}$$

Worked example

Input. Male, 35 y, 85 kg, 178 cm, lightly active (1.375), lose 7 kg in 12 weeks.

• BMR = 10×85 + 6.25×178 − 5×35 + 5 = 1,792 kcal
• TDEE = 1,792 × 1.375 = 2,467 kcal
• Deficit needed = 7×7,700 ÷ 84 = 642 kcal/day
• Daily target = 2,467 − 642 = 1,825 kcal
• Macros ≈ 137 g protein, 182 g carbs, 61 g fat

Quick-Facts

• Safe loss rate: 0.5–1 kg week⁻¹ (CDC, 2023).
• 7,700 kcal ≈ 1 kg of body fat (Hall et al., 2008).
• Activity factors range 1.2–1.9 (FAO/WHO/UNU, 2004).
• AMDR: 45–65 % carbs, 10–35 % protein, 20–35 % fat (US Dietary Guidelines 2020-25).
• Mifflin-St Jeor predicts resting energy within 10 % for most adults (Frankenfield, 2005).

What is BMI?

BMI compares your weight to height and flags underweight (<18.5), normal (18.5–24.9), overweight (25–29.9) or obesity (≥30) classes (WHO, 2022).

How does the calculator estimate daily calories?

It multiplies Mifflin-St Jeor BMR by an activity factor—1.2 (sedentary) to 1.9 (extra active)—to yield TDEE (FAO/WHO/UNU, 2004).

What deficit should you aim for?

Create a 500–750 kcal daily deficit to lose 0.5–1 kg weekly without compromising nutrition (ACE, 2022).

What is a healthy rate of weight loss?

Losing 0.5–1 kg per week maximizes fat reduction while preserving lean mass (CDC, 2023).

How should you split macros?

Use 1.4–2.0 g protein kg⁻¹ day⁻¹ for muscle retention (Phillips, 2016) and balance remaining calories 40 % carbs, 30 % fat.

Can you enter pounds and inches?

Yes—choose “lbs” and “ft / in”. The tool converts to metric internally (1 lb = 0.4536 kg; 1 in = 2.54 cm) (NIST, 2019).

Why does activity level matter?

Higher activity boosts daily energy burn, so calorie targets rise accordingly to maintain the same deficit (FAO/WHO/UNU, 2004).

What if weight loss stalls?

Re-measure intake, increase activity, or reduce calories by an extra 100–200 kcal; metabolic adaptation can lower TDEE by 5–15 % (Rosenbaum, 2018).