Reweight Calculator

Safe weight loss is typically 0.25–0.5 kg/week. Max sustainable: ~1 kg/week.

Reweight Calculator — Guide & Formula

The Reweight Calculator tells you how many weeks and days it will take to reach your target weight at a given weekly rate of loss or gain. It also estimates the required daily calorie deficit or surplus.

Formula

• Total change = |current weight − target weight| (kg)
• Weeks to goal = total change ÷ weekly rate
• Daily calorie deficit/surplus = weekly rate × 7,700 ÷ 7

What is 7,700 kcal per kg?

Pure fat tissue contains approximately 9 kcal per gram (9,000 kcal/kg), but body weight change is a mix of fat, water, and lean tissue. An average effective caloric value of ~7,700 kcal per kg of body weight change is widely used in clinical and dietary practice.

Tips for reaching your goal

• Combine calorie reduction with regular physical activity
• Prioritise protein intake (1.6–2.2 g/kg body weight) to preserve muscle
• Track progress weekly, not daily (daily weight fluctuates 1–2 kg due to water)
• Losing more than 1 kg/week typically results in significant muscle loss

References

• Hall KD et al. (2011). "Quantification of the effect of energy imbalance on bodyweight." Lancet 378(9793):826–837.
• Stiegler P, Cunliffe A (2006). "The role of diet and exercise for the maintenance of fat-free mass." Sports Med 36(3):239–262.

How Reweighing Works for Accurate Progress Tracking

Body weight fluctuates by 1–3 kg (2–6 lb) throughout a single day due to food, water, and bowel contents. Weighing at a consistent time — first thing in the morning after using the bathroom — gives the most reproducible readings. Taking a 7-day moving average removes noise, revealing the true underlying trend. Studies show people who weigh daily and track the moving average lose more weight and maintain it better than those who weigh weekly or monthly.

Causes of Short-Term Weight Fluctuations