Weight Loss Calculator
Calculate your daily calorie target, weekly loss rate, and exact goal date with a personalized weight loss plan
Your Weight Loss Plan
Understanding Weight Loss and Calorie Deficits
Weight loss fundamentally comes down to energy balance: you must consume fewer calories than your body expends over a sustained period. Your Total Daily Energy Expenditure (TDEE) represents the total calories your body burns each day through basal metabolism, the thermic effect of food, and physical activity. When you eat below your TDEE, your body draws on stored energy (primarily body fat) to make up the difference, resulting in weight loss. One pound of body fat contains approximately 3,500 calories of stored energy, so a daily deficit of 500 calories translates to roughly one pound of fat loss per week.
The rate at which you lose weight matters as much as the total amount. Research consistently shows that losing 0.5 to 1 kilogram (1 to 2 pounds) per week is the sweet spot for preserving lean muscle mass while reducing body fat. Faster rates of loss are associated with greater muscle catabolism, metabolic adaptation (where your metabolism slows disproportionately), nutritional deficiencies, and a higher probability of regaining the weight. This calculator checks your projected loss rate against these evidence-based thresholds and warns you if your timeline is too aggressive.
Weight loss is rarely perfectly linear. You will likely experience weeks where the scale does not move or even goes up slightly, followed by sudden drops. This is normal and caused by water retention fluctuations, hormonal cycles, sodium intake changes, and bowel contents. The projected curve in this calculator shows a smooth mathematical projection, but your real-world path will zigzag around it. Focus on the four-week moving average rather than any single weigh-in. If your average weight is trending downward over a month, your plan is working.
Sustainability is the most critical factor in any weight loss plan. The best calorie target is one you can maintain consistently for the full duration of your timeline without feeling deprived or exhausted. Most nutrition professionals recommend never dropping below 1,200 calories per day for women or 1,500 for men without medical supervision. If this calculator shows that your goal requires an uncomfortably low calorie intake, the solution is to either extend the timeline, increase physical activity to raise your TDEE, or adjust the goal weight to a more realistic target. Small, consistent deficits beat extreme restriction every time.
How to Use This Calculator
- Select your preferred unit system (Metric or Imperial) using the toggle at the top of the form. All weight and height fields will update accordingly.
- Enter your current weight, goal weight, age, height, and select your gender. Accurate inputs lead to more reliable results.
- Set your timeline in weeks. The calculator recommends 12-52 weeks for most goals. Shorter timelines may trigger safety warnings if the required deficit is too large.
- Select the activity level that honestly reflects your typical week, from sedentary (desk job) to extra active (athlete).
- Click 'Calculate Weight Loss Plan' to see your daily calorie target, weekly loss rate, projected weight curve, goal date calendar, and safety assessment. Adjust your timeline if any warnings appear.
Frequently Asked Questions
How does this calculator determine my daily calorie target?
The calculator first estimates your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, which accounts for your weight, height, age, and gender. It then multiplies your BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE). Finally, it subtracts the calorie deficit needed to lose the required weight within your specified timeline. For example, if you need to lose 10 kg in 20 weeks (0.5 kg/week), and each kilogram of fat contains roughly 7,700 calories, you need a daily deficit of about 550 calories. Your target intake is TDEE minus that deficit.
What is a safe rate of weight loss per week?
Most health organizations and clinical guidelines recommend losing 0.5 to 1 kg (1 to 2 lbs) per week. This rate preserves lean muscle mass, minimizes metabolic adaptation, and is sustainable long-term. Losing more than 1 kg per week consistently may lead to muscle loss, gallstones, nutritional deficiencies, and a higher likelihood of regaining the weight. If your plan shows a weekly loss rate above 1 kg, consider extending your timeline.
Why does the calculator warn me about low calorie intake?
Eating below 1,200 calories per day (for women) or 1,500 calories per day (for men) is generally considered unsafe without medical supervision. Very low calorie diets can cause fatigue, hair loss, hormonal disruption, immune suppression, and severe metabolic slowdown. If your desired timeline requires calories below these thresholds, the calculator flags it as dangerous and recommends either extending the timeline or adjusting the goal weight.
How accurate is the projected weight loss curve?
The projected curve is a mathematical model based on a consistent daily calorie deficit. In reality, weight loss slows over time because your body requires fewer calories as it gets lighter (your TDEE decreases). The curve accounts for this by recalculating at each time step. However, it cannot predict water retention fluctuations, diet adherence variations, or metabolic adaptation. Use the curve as a general guide and track your actual weight alongside it to assess progress.
Does activity level really make that big a difference?
Yes, enormously. The activity multiplier ranges from 1.2 (sedentary) to 1.9 (extra active), which means the same person could have a TDEE difference of over 1,000 calories depending on their activity level. Higher activity means a higher TDEE, which allows you to eat more while still maintaining a deficit, or reach your goal faster at the same calorie intake. Even small increases in daily movement (walking more, taking stairs) can meaningfully raise your TDEE and make your weight loss plan more comfortable.
Should I eat back the calories I burn from exercise?
The activity level you select already factors exercise into your TDEE calculation, so you generally should not add extra calories for individual workouts. If you do a particularly intense session beyond your normal routine, you might eat back 30-50% of those extra calories to support recovery, but most people overestimate exercise calorie burn. A safer approach is to select your activity level honestly and let the TDEE calculation handle the math. If you find yourself consistently fatigued or losing weight faster than projected, you may need to eat slightly more.
What happens when I reach my goal weight?
When you reach your goal weight, you should gradually increase your calorie intake toward your new TDEE (which will be lower than when you started, since you weigh less). Do not jump immediately to maintenance calories. Instead, add 100-200 calories per week over 4-8 weeks, a process called reverse dieting. This allows your metabolism to adjust upward and helps prevent the rapid weight regain that commonly occurs after a diet ends. Continue monitoring your weight weekly and adjust as needed to stabilize.
