See how long it will take to reach your target weight
This calculator provides estimates only. Consult your GP or a healthcare professional for personalised advice. Actual results vary based on metabolism, activity level, and adherence.
One of the most common questions people ask when starting a weight loss journey is "how long will it take?" This calculator answers that question by projecting your weight loss timeline based on a daily calorie deficit. It uses the well-established principle that approximately 7,700 calories (kcal) are stored in one kilogram of body fat, so a known daily deficit translates directly into a predictable rate of fat loss. The NHS recommends losing weight gradually at a rate of 0.5 to 1 kg per week for sustainable, long-term results. Rapid weight loss through very low calorie diets (under 800 kcal per day) should only be attempted under medical supervision. This calculator lets you choose from four deficit levels, ranging from a gentle 250 calories per day to a maximum of 1,000 calories per day, so you can see how different approaches affect your timeline. Understanding your projected timeline helps set realistic expectations. Many people underestimate how long healthy weight loss takes and become discouraged when they do not see rapid results. By seeing the numbers upfront, you can choose a sustainable pace and plan accordingly.
To use this calculator: 1. Enter your current weight in kilograms. If you know your weight in stones, multiply by 6.35 to convert. For example, 14 stone = 88.9 kg. 2. Enter your target weight in kilograms. This should be a realistic goal, ideally within a healthy BMI range for your height. 3. Select your daily calorie deficit: - Gentle (250 cal/day): slow but very sustainable, about 0.25 kg per week - Moderate (500 cal/day): the NHS-recommended level, about 0.5 kg per week - Aggressive (750 cal/day): faster results but harder to maintain, about 0.75 kg per week - Maximum (1,000 cal/day): the upper limit for unsupervised weight loss, about 1 kg per week 4. Review your results: - Total weeks and months needed to reach your target - Estimated target date - Weekly weight loss rate in kilograms - Total weight to lose 5. The line chart shows your projected weight week by week, giving you a visual roadmap of your journey.
The calculation is based on the energy balance principle: Weekly Weight Loss (kg) = (Daily Calorie Deficit x 7) / 7,700 The number 7,700 represents the approximate number of calories stored in one kilogram of body fat. By creating a daily deficit, you force your body to use stored fat for energy. Weeks Needed = Total Weight to Lose / Weekly Weight Loss (rounded up) For example, to go from 90 kg to 75 kg with a 500 calorie daily deficit: Weekly Loss = (500 x 7) / 7,700 = 3,500 / 7,700 = 0.45 kg/week Total to Lose = 90 - 75 = 15 kg Weeks Needed = 15 / 0.45 = 33.3, rounded up to 34 weeks At the moderate deficit level, it would take about 34 weeks (roughly 8 months) to lose 15 kg. Doubling the deficit to 1,000 calories per day would halve the timeline to about 17 weeks, but maintaining such a large deficit requires careful planning and may not be sustainable for everyone. The calculator caps the projection at 104 weeks (2 years). If your goal requires a longer timeline, consider adjusting your target or increasing your deficit slightly.
Inputs: Current Weight: 90 kg, Target Weight: 75 kg, Deficit: 500 cal/day
Inputs: Current Weight: 80 kg, Target Weight: 75 kg, Deficit: 1,000 cal/day
Inputs: Current Weight: 95 kg, Target Weight: 85 kg, Deficit: 250 cal/day
This calculator uses a simplified linear model. In practice, weight loss often slows as you get lighter because your body requires fewer calories to maintain a lower weight. Your basal metabolic rate decreases, and the same calorie deficit produces a smaller percentage of weight loss over time. For this reason, the timeline should be treated as an estimate rather than a guarantee. The NHS recommends reassessing your calorie intake and activity levels every few months to account for these changes.