How the Weight Loss Calculator Works
This calculator models your weight loss journey by combining three core principles:
- Set your goal: Enter your current weight and target weight. The calculator computes the total energy deficit required based on the standard guideline of 7,700 kcal per 1 kg (3,500 kcal per 1 lb) of body fat.
- Choose your pace: Select a weekly weight loss rate — relaxed (0.25 kg/week), normal (0.5 kg/week), or strict (1 kg/week). This determines your daily and weekly calorie deficit targets.
- Plan your exercise: Either specify how much time you have for sports, or pick a specific activity. The calculator recommends activities and shows what percentage of your deficit is covered by exercise vs. diet.
- View your timeline: See how many weeks until you reach your goal, along with detailed exercise plans and deficit breakdowns.
Weight Loss Calculator Formula
The fundamental weight loss equation is based on energy balance:
Total Deficit = Weight to Lose (kg) × 7,700 kcal/kg
Weekly Deficit = Pace (kg/week) × 7,700 kcal/kg
Daily Deficit = Weekly Deficit ÷ 7
Exercise calories are calculated using the MET formula: Calories = MET × 3.5 × Weight (kg) ÷ 200 × Duration (min). The remaining deficit after exercise must come from dietary adjustments.
BMR vs. TDEE Explained
Understanding the difference between BMR and TDEE is critical for effective weight loss planning:
- BMR (Basal Metabolic Rate) — the calories your body burns at absolute rest, just to maintain vital functions like breathing, circulation, and cell repair. BMR typically accounts for 60–75% of total daily calories. Calculated using the Mifflin-St Jeor equation based on age, sex, weight, and height.
- TDEE (Total Daily Energy Expenditure) — your BMR multiplied by an activity factor. TDEE includes everything: your resting metabolism, daily movements, exercise, and the thermic effect of food (calories burned digesting). To lose weight, you must eat below your TDEE, not below your BMR.
Eating below your BMR for extended periods can slow your metabolism and lead to muscle loss. A sustainable deficit targets 15–25% below TDEE.
Calorie Deficit Chart for Weight Loss
This chart shows estimated weight loss based on different daily calorie deficits, assuming the standard 7,700 kcal = 1 kg of fat:
| Daily Deficit | Weekly Deficit | Weekly Weight Loss | Monthly Weight Loss |
|---|---|---|---|
| 250 kcal | 1,750 kcal | 0.23 kg (0.5 lb) | ~0.9 kg (2.0 lbs) |
| 500 kcal | 3,500 kcal | 0.45 kg (1.0 lb) | ~1.8 kg (4.0 lbs) |
| 750 kcal | 5,250 kcal | 0.68 kg (1.5 lbs) | ~2.7 kg (6.0 lbs) |
| 1,000 kcal | 7,000 kcal | 0.91 kg (2.0 lbs) | ~3.6 kg (8.0 lbs) |
A deficit of 500–750 kcal per day is widely recommended as safe and sustainable. Larger deficits increase the risk of metabolic slowdown and nutritional deficiency.
How to Use This Calculator to Set a Realistic Goal
Setting the right target makes the difference between sustainable success and burnout. Here's how to get the most from this calculator:
- Start conservative: If you're new to calorie tracking, begin with the "Relaxed" pace (0.25 kg/week). You can always increase the intensity once the habit is established.
- Balance exercise and diet: The progress bar at the bottom of the results shows what percentage of your deficit comes from exercise vs. dietary changes. Aim for a healthy split — ideally 40–60% from exercise.
- Be honest about exercise time: Overestimating workout frequency is the #1 reason weight loss plans fail. Input only the time you can genuinely commit to each week.
- Recalculate monthly: As you lose weight, your calorie needs decrease. Re-run the calculator every 2–4 weeks with your updated weight for accurate projections.
Building a Sustainable, Active Lifestyle
Weight loss isn't just about hitting a number — it's about building habits that last. Research consistently shows that people who maintain weight loss long-term share these traits:
- Consistent physical activity: Aim for 150–300 minutes of moderate exercise per week. This doesn't have to be intense — regular walking counts.
- Progressive overload: Gradually increase exercise intensity or duration over time. Start with 3 sessions per week and build to 4–5 as fitness improves.
- Variety: Mix activities to prevent boredom and work different muscle groups. Alternate between walking, cycling, swimming, and strength training.
- Sleep and recovery: Poor sleep increases hunger hormones (ghrelin) and decreases satiety hormones (leptin). Aim for 7–9 hours per night.
- Track without obsessing: Use this calculator as a guide, not a rigid prescription. Small fluctuations are normal — focus on weekly and monthly trends.
FAQs
What's the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the energy your body burns at complete rest — just to keep you alive. TDEE (Total Daily Energy Expenditure) is your BMR plus all the additional calories you burn through daily activities, exercise, and digestion. TDEE is always higher than BMR and is the number you should use when planning a calorie deficit for weight loss.
How do I calculate my TDEE?
TDEE = BMR × Activity Multiplier. First, calculate your BMR using the Mifflin-St Jeor equation (based on age, sex, weight, and height). Then multiply by an activity factor: 1.2 (sedentary), 1.375 (light exercise 1–3 days/week), 1.55 (moderate exercise 3–5 days/week), 1.725 (hard exercise 6–7 days/week), or 1.9 (very hard exercise plus physical job). The result is your estimated daily calorie needs.
How many calories do I burn walking 1 hour?
A 70 kg person burns approximately 280 kcal walking at a moderate pace (3 mph) for one hour. The exact number depends on your weight, walking speed, and terrain. For a precise calculation, use our Walking Calorie Calculator which factors in slope, sex, stride length, and speed.
How much of a calorie deficit is safe per day?
Most health authorities recommend a daily deficit of 500–750 kcal, which translates to a weight loss of approximately 0.5–0.75 kg (1–1.5 lbs) per week. Deficits exceeding 1,000 kcal per day can trigger metabolic adaptation, muscle loss, and nutritional deficiencies. The ideal deficit combines moderate dietary reduction (~300–500 kcal) with increased physical activity (~200–300 kcal).