Weight Loss Calculator
Use a calorie-deficit model to estimate weekly fat-loss pace and roughly how long a target weight may take.
How to use this weight loss calculator
- Enter current weight
Enter your current body weight in the current weight field.
- Enter target weight
Enter the goal weight you want to reach in the target weight field.
- Enter maintenance calories
Enter your estimated TDEE or maintenance calories in the maintenance calories field.
- Enter planned intake
Enter the daily calorie intake you plan to follow in the planned daily intake field.
- Review timeline
Check the estimated daily deficit, weekly weight loss pace, and projected target date.
How this weight loss calculator works
This weight loss calculator uses a simple energy-balance model: if your calorie intake stays below maintenance, the deficit accumulates over time and can be translated into expected weight change. It combines your current weight, target weight, maintenance calories, and planned intake to estimate the daily deficit, weekly pace, and rough timeline to the goal.
Daily deficit = TDEE − daily intake
Weekly weight loss (kg) = (daily deficit × 7) ÷ 7,700
Estimated weeks to goal = (current weight − target weight) ÷ weekly weight loss Daily deficit = TDEE − daily intake
Weekly weight loss (lb) = (daily deficit × 7) ÷ 3,500
Estimated weeks to goal = (current weight − target weight) ÷ weekly weight loss If current weight is 85 kg, target weight is 75 kg, maintenance calories are 2,400, and planned intake is 1,900, the daily deficit is 500 calories. Over a week that is 3,500 calories, which corresponds to about 0.45 kg of expected weekly loss. Losing 10 kg at that pace takes roughly 22 weeks, assuming consistency and no major changes in maintenance calories.
If current weight is 187 lb, target weight is 165 lb, maintenance calories are 2,400, and planned intake is 1,900, the daily deficit is 500 calories. Over a week that is 3,500 calories, which corresponds to about 1 lb of expected weekly loss. Losing 22 lb at that pace takes roughly 22 weeks, assuming consistency and no major changes in maintenance calories.
If current weight is 70 kg, target weight is 62 kg, maintenance calories are 2,100, and planned intake is 1,700, the daily deficit is 400 calories. Over a week that is 2,800 calories, which corresponds to about 0.36 kg of expected weekly loss. Losing 8 kg at that pace takes roughly 22 weeks.
If current weight is 100 kg, target weight is 85 kg, maintenance calories are 2,800, and planned intake is 2,200, the daily deficit is 600 calories. Over a week that is 4,200 calories, which corresponds to about 0.55 kg of expected weekly loss. Losing 15 kg at that pace takes roughly 27 weeks.
- ✓ The estimate assumes your stated maintenance calories are reasonably accurate at the start of the plan.
- ✓ The model uses a simplified 7,700 kcal per kilogram planning rule, which is useful directionally but does not capture all metabolic adaptation.
- ✓ Daily intake and activity are assumed to stay reasonably consistent throughout the modeled period.
- ✓ Real-world weight change is noisy because of water retention, glycogen changes, hormones, and adherence.
- A moderate calorie deficit is usually easier to sustain and easier to recover from than an aggressive cut that hurts training, sleep, or adherence.
- As body weight drops, maintenance calories usually drop too, so long plans often need periodic recalibration.
- Use trend weight over several weeks rather than reacting to daily scale swings, which are heavily influenced by fluids and glycogen.
- Hall, K.D. et al., 'Quantification of the Effect of Energy Imbalance on Bodyweight,' The Lancet, 2011
- NIH Body Weight Planner methodology
- Academy of Nutrition and Dietetics — weight-management evidence summary
How calorie deficits drive weight loss
Weight loss occurs when you consistently consume fewer calories than your body expends, creating what is known as a calorie deficit. Your body makes up the energy shortfall by drawing on stored fuel, primarily body fat but also some glycogen and, in certain conditions, muscle protein. The commonly used planning figure of 7,700 kilocalories per kilogram of body fat (or 3,500 per pound) provides a rough conversion between cumulative deficit and expected weight change. In reality, the relationship is not perfectly linear because the body adjusts its metabolic rate, hormonal signalling, and spontaneous movement in response to prolonged under-eating — a phenomenon often called metabolic adaptation. Despite these nuances, the deficit model remains the most practical framework for setting initial calorie targets and estimating timelines, as long as you treat the output as a starting estimate rather than a precise prediction.
Setting a realistic weight loss timeline
One of the most common mistakes in weight-loss planning is choosing a deficit so aggressive that it becomes impossible to sustain. A weekly loss rate of roughly 0.25 to 0.75 kg (about 0.5 to 1.5 lb) is a widely recommended range for most adults because it is aggressive enough to produce visible progress over weeks but moderate enough to preserve muscle mass, maintain energy for daily activities, and avoid the rebound overeating that often follows extreme restriction. People with more weight to lose can sometimes sustain the higher end of that range, while those closer to their goal may need to accept the lower end. Building in periodic diet breaks — planned weeks at maintenance calories — can help manage hunger hormones and psychological fatigue during longer fat-loss phases. Reviewing progress every two to four weeks and adjusting intake or activity when the trend stalls is far more effective than rigidly following an initial plan that no longer matches your current metabolic state.
Weight loss calculator FAQs
How accurate is the timeline estimate?
It is a planning estimate, not a guarantee. Real weight loss is rarely linear because maintenance calories change over time and daily body weight fluctuates for reasons unrelated to fat loss.
Why does the calculator require maintenance calories?
Because the size of the calorie deficit depends on the gap between what you burn and what you eat. Without a maintenance estimate, the model cannot calculate expected pace.
What is a reasonable weekly fat-loss pace?
For many adults, roughly 0.25 to 0.75 kg per week is a practical range. Faster rates are possible but often harder to sustain and more likely to affect training, recovery, or lean mass.
What if my planned intake is not below maintenance?
Then you do not have a calorie deficit, so the model will not produce a valid weight-loss timeline. Intake needs to be below maintenance for fat loss to occur.