What this tool does and when to use it
This calculator turns your current weight, goal weight and a weekly pace into a daily calorie target and a goal date. It uses the Mifflin St Jeor equation for maintenance calories, then simulates your loss week by week at your new weight, so the date stays honest as progress slows. It never sets an intake below 1,200 kcal for women or 1,500 kcal for men. Use it to plan a realistic timeline, then recalculate every 5 kg or so.
How the weight loss calculator works
We start with your maintenance calories, your total daily energy expenditure, from the Mifflin St Jeor equation and your activity level. Losing about 1 kg of body fat takes a deficit of roughly 7,700 kcal (about 3,500 kcal per pound), so a pace of 0.5 kg a week needs a daily deficit of about 550 kcal.
Most calculators stop there and assume the same deficit every week. But as you lose weight, your body needs fewer calories, so the same intake produces a smaller deficit over time. Our calculator recalculates your maintenance every week at your new weight, which gives a more honest goal date and shows you if progress would stall.
How fast should I lose weight?
Health agencies such as the CDC and NHS recommend about 0.5 to 1 kg (1 to 2 lb) a week. Losing faster usually means more muscle loss, more hunger and a higher chance of regaining weight. We also keep your intake at or above 1,200 kcal for women and 1,500 kcal for men, since going lower without medical supervision makes it hard to get enough nutrients.
| Pace | Daily deficit | Best for |
|---|---|---|
| 0.25 kg (0.5 lb) a week | About 275 kcal | The last few kilos, or a very comfortable pace |
| 0.5 kg (1 lb) a week | About 550 kcal | Most people, sustainable long term |
| 0.75 kg (1.5 lb) a week | About 825 kcal | Larger starting weights |
| 1 kg (2 lb) a week | About 1,100 kcal | Short phases with plenty to lose |
How long does it take to lose 10, 20, 30 or 50 pounds?
We ran this calculator for two example adults aged 35 with light activity (exercise 1 to 3 days a week): a 5 ft 5 in woman and a 5 ft 10 in man, both starting at 180 lb (200 lb for the 50 lb goal). Your own numbers will differ, so enter your details above for a personal date.
| Weight to lose | Steady pace, woman | Steady pace, man | Maximum pace, woman | Maximum pace, man |
|---|---|---|---|---|
| 10 lb (180 to 170) | 10 weeks | 10 weeks | 6 weeks | 6 weeks |
| 20 lb (180 to 160) | 21 weeks | 21 weeks | 13 weeks | 12 weeks |
| 30 lb (180 to 150) | 34 weeks | 34 weeks | 20 weeks | 19 weeks |
| 50 lb (200 to 150) | 66 weeks | 67 weeks | 30 weeks | 29 weeks |
Two things stand out. First, a steady 1 lb a week turns 50 pounds into about 66 weeks rather than 50, because the same intake gives a smaller deficit as you lose. Second, the maximum pace of 2 lb a week was capped in every run: it would have needed fewer than 1,200 kcal a day for the woman and 1,500 kcal for the man, so the calculator held intake at those floors. That is why the maximum pace roughly halves the time instead of doing better.
Tips that make it stick
- Eat plenty of protein and vegetables to stay full on fewer calories.
- Add strength training two or three times a week to protect muscle.
- Sleep seven to nine hours, since poor sleep increases hunger.
- Recalculate every 5 kg or so, or use the milestones above as check points.
Pick a healthy goal first with the ideal weight calculator, set your macros with the calorie calculator, or try a low carb approach with the keto calculator and meal plan.
Sources: Mifflin St Jeor equation (1990); CDC and NHS guidance on healthy weight loss; Hall KD et al. on dynamic energy balance, The Lancet 2011.
