Weight Loss Calculator

0.5–1% of total bodyweight per week is widely considered the safe, sustainable range by dietitians and sports scientists — for a 90kg person, that's roughly 0.45–0.9kg per week. This calculator offers rates from 0.25kg (gentle) up to 1kg (aggressive) per week. Faster rates increase the risk of muscle loss, nutrient deficiency, gallstone formation, metabolic adaptation, and rebound weight regain. Slower, more gradual rates are generally easier to sustain long-term and better preserve muscle mass, especially when combined with resistance training and adequate protein intake.

The target date is a projection based on the assumption that you maintain a consistent calorie deficit throughout the period — in reality, weight loss is rarely perfectly linear. You'll likely see faster loss in the first 1–2 weeks (partly water weight), followed by a more gradual, sometimes plateauing trajectory, occasional weeks of little change due to water retention or hormonal factors, and the need to recalculate your calorie target as your weight decreases (since a lighter body needs fewer calories to maintain itself). Treat the date as a reasonable estimate and general planning guide rather than a guarantee.

The deficit is derived directly from your chosen weekly weight loss rate, using the approximation that 1kg of body fat represents roughly 7,700 kcal of stored energy. So a 0.5kg/week goal requires a daily deficit of approximately 550 kcal (7,700 × 0.5 ÷ 7), and a 1kg/week goal requires roughly 1,100 kcal/day. If you provide your age, height, sex, and activity level, the calculator also estimates your TDEE (using the Mifflin-St Jeor formula) and subtracts this deficit to give you a personalised daily calorie target rather than just an abstract deficit number.

As you lose weight, your TDEE (total daily calorie burn) decreases, both because a smaller body requires fewer calories for basic functions and movement, and because of some degree of metabolic adaptation from sustained dieting. This means the same daily calorie intake that produced a 0.5kg/week loss early on will produce a smaller effective deficit — and slower loss — later in your journey, unless you periodically recalculate and adjust your calories downward. Many experienced dieters intentionally choose a slower rate as they approach their goal weight specifically to make this transition more manageable and sustainable.

Some muscle loss during a calorie deficit is common, but the amount can be substantially minimised through two key strategies: maintaining adequate protein intake (generally 1.2–1.6g per kg of bodyweight, and often higher for leaner individuals) and continuing resistance training throughout your weight loss phase. Without these two elements, a meaningful proportion of weight lost can come from muscle rather than fat — sometimes as much as 25–30% of total weight lost in unfavourable conditions (low protein, no resistance training, very aggressive deficit). With adequate protein and consistent resistance training, this proportion typically drops considerably, preserving most of your lean mass while losing predominantly fat.

Weight loss plateaus are extremely common and usually reflect one of a few things: your TDEE has genuinely decreased as you've lost weight, meaning your current calorie intake and your new (lower) maintenance level have converged; water retention is temporarily masking real fat loss (common around hormonal cycles, high-sodium meals, or increased training stress); or tracking has become less precise over time (portion creep, forgotten snacks or drinks). First, verify you're accurately tracking intake for a week. If the plateau persists beyond 2–3 weeks with accurate tracking, recalculate your calorie target based on your current (lower) weight, or introduce a short diet break at maintenance calories for 1–2 weeks to help reset hunger hormones before resuming the deficit.

Slower, more gradual weight loss (0.5% or less of bodyweight per week) generally produces better long-term outcomes across several dimensions: greater muscle preservation, lower risk of metabolic adaptation, better adherence and less hunger/irritability, and — critically — better maintenance of results afterward, since gradual changes are more likely to reflect genuinely sustainable habit changes rather than a temporary extreme diet. Faster weight loss can be appropriate short-term in specific medical contexts (under supervision) or for people with a very large amount of weight to lose initially, but for most people pursuing general fat loss, the evidence favours the "boring but effective" gradual approach.

A calorie deficit through diet alone is sufficient to produce weight loss — exercise is not strictly required for the number on the scale to go down. However, exercise (particularly resistance training) provides substantial additional benefits: it helps preserve muscle mass during the deficit (meaning more of the weight lost is fat, not muscle), makes it easier to sustain a deficit by increasing total calorie expenditure, and offers wide-ranging health benefits independent of weight (cardiovascular health, bone density, mood, insulin sensitivity) that diet alone doesn't provide. For the best body composition outcome (not just lower scale weight, but a leaner, more muscular physique), combining a moderate calorie deficit with regular resistance training is the most evidence-supported approach.

Activity level is a core input for estimating your TDEE (Total Daily Energy Expenditure) — the baseline number of calories you burn per day before any deficit is applied. Someone who trains hard 6 days a week burns considerably more calories daily than someone with a sedentary lifestyle, even at the same bodyweight, height, age, and sex. Without an accurate activity level, the calorie target calculated would be based on a fundamentally wrong baseline, leading to either too large or too small a real-world deficit regardless of how well you stick to the numbers.

Yes — sustainable weight loss is about total calorie balance over time, not eliminating entire food categories or specific "bad" foods. Most evidence-based approaches to fat loss (flexible dieting, "if it fits your macros" approaches, and structured meal plans alike) allow moderate inclusion of less nutrient-dense, more indulgent foods within your overall calorie target, since research consistently shows that overly restrictive diets that eliminate entire food groups or specific treats tend to have worse long-term adherence and higher rates of binge eating or rebound weight regain compared to more flexible, moderate approaches.

Daily weight can fluctuate by 1–3kg due to factors unrelated to actual fat loss: sodium intake (higher sodium meals cause water retention), carbohydrate intake (each gram of stored glycogen holds roughly 3g of water, so lower-carb days or meals show lower water-linked weight), hormonal cycles in women, recent exercise (causing temporary inflammation and water retention in worked muscles), and simply the volume of food and fluid recently consumed. This is precisely why tracking a weekly rolling average of your weight (rather than reacting to any single day's number) gives a far more accurate picture of your true weight loss trend.

Transition gradually from your deficit back to maintenance calories rather than abruptly — increase your intake by roughly 100–150 kcal every 1–2 weeks until you reach your new (lower, since you now weigh less) TDEE, giving your body and habits time to adjust. This gradual "reverse diet" approach helps minimise rapid rebound weight gain compared to suddenly returning to old eating habits. Continue tracking your weight periodically (weekly average) to catch any drift early, and maintain the exercise and protein habits that helped you lose the weight in the first place, since these are equally important for long-term weight maintenance.