Weight Loss Calculator & Gain Calculator
Weight Loss Calculator
How Long to Reach Your Goal?
Enter your details and instantly get your exact calorie deficit, personalised goal timeline, weekly plan, macro split, and milestone dates. WhatsApp share and free PDF report included. Based on the Mifflin-St Jeor equation used by dietitians worldwide.
How Long Will It Take to Lose Weight?
Weight loss timelines vary enormously depending on starting weight, activity level, calorie deficit size, and individual metabolic factors. This calculator uses the Mifflin-St Jeor equation -- the most accurate formula recognised by the Academy of Nutrition and Dietetics -- to calculate your personalised TDEE and then applies your chosen deficit to generate a realistic, science-based timeline.
Remember that the timeline assumes perfect consistency. Real weight loss is rarely perfectly linear -- you may lose faster initially (largely water weight and glycogen depletion) and slower later as your body adapts. Check your BMI to understand where you are starting from and our Ideal Weight Calculator to set a realistic, healthy goal weight.
What Is a Calorie Deficit and How Does It Work?
A calorie deficit is the state of consuming fewer calories than your body burns. Your TDEE (Total Daily Energy Expenditure) is the total number of calories you burn each day through all activity -- from breathing and organ function (your BMR) to exercise and daily movement. When you eat below your TDEE, your body is forced to draw on its stored energy -- primarily body fat -- to make up the shortfall.
The maths is straightforward: one kilogram of body fat stores approximately 7,700 calories. A daily deficit of 500 calories creates a weekly deficit of 3,500 calories, equating to approximately 0.45 kg (1 lb) of fat loss per week. This relationship is known as the "3,500 calorie rule" and while not perfectly precise (the body adapts), it is a robust and clinically validated planning tool.
Use our Calorie Calculator to find your exact TDEE and daily calorie target. To further increase your deficit without eating less, use our Calories Burned Calculator to understand how much additional deficit exercise creates, or our Steps to Calories Calculator to see how daily walking contributes.
What Is a Safe Rate of Weight Loss?
The WHO, NHS, and Academy of Nutrition and Dietetics all recommend a weight loss rate of 0.5 to 1 kg (1 to 2 lbs) per week as safe and sustainable. This corresponds to a daily calorie deficit of approximately 500-750 calories. This pace:
- Preserves the maximum amount of muscle mass
- Avoids significant metabolic slowdown (adaptive thermogenesis)
- Is sustainable long-term without causing fatigue, nutritional deficiencies, or rebound eating
- Allows time for skin elasticity to adjust
- Is associated with significantly better long-term weight maintenance outcomes
Faster weight loss (1-2 kg per week) is sometimes appropriate for people with very high starting BMI under medical supervision. However, rapid weight loss diets consistently produce higher rates of muscle loss, greater metabolic adaptation, and higher rates of weight regain. Check your Body Fat percentage to understand whether you have primarily fat to lose or whether muscle preservation should be an extra priority.
| Daily Deficit | Weekly Loss | Monthly Loss | 10 kg in... |
|---|---|---|---|
| 250 calories (slow) | ~0.25 kg | ~1 kg | ~40 weeks |
| 500 calories (recommended) | ~0.5 kg | ~2 kg | ~20 weeks |
| 750 calories (fast) | ~0.75 kg | ~3 kg | ~13 weeks |
| 1000 calories (aggressive) | ~1 kg | ~4 kg | ~10 weeks |
Why Does Weight Loss Stall? (And How to Fix It)
Weight loss plateaus are almost universal after 6-12 weeks of dieting. Understanding why they happen is key to breaking through them. The main reasons are:
1. Adaptive Thermogenesis
When you eat less, your body responds by reducing its metabolic rate -- sometimes by 200-400 calories per day. This means your actual TDEE is now lower than your calculated TDEE, and your deficit has shrunk or disappeared. The fix: recalculate your calories at your new lower weight and reduce intake by 100-200 calories.
2. Muscle Loss
Without sufficient protein and resistance training, calorie restriction causes muscle loss. Less muscle means a lower BMR and therefore a lower TDEE. This is why the protein target in the macro section of this calculator is high -- maintaining muscle during a deficit is critical. Check your protein needs with our Macro Calculator.
3. Inaccurate Tracking
Research consistently shows that people underestimate their calorie intake by 20-50%. This happens through forgetting snacks, underestimating portion sizes, not counting cooking oils and sauces, and not accounting for liquid calories (juices, alcohol, coffee drinks). Even small systematic errors of 100-200 calories per day can completely offset a 250-500 calorie deficit.
4. Poor Sleep
Sleep deprivation significantly increases ghrelin (hunger hormone) and decreases leptin (satiety hormone), leading to an average of 385 extra calories consumed per day in research studies. It also raises cortisol, which promotes fat storage particularly around the abdomen. Use our Sleep Calculator to optimise your sleep cycles for better weight loss results.
5. Stress and Cortisol
Chronic psychological stress elevates cortisol, which drives fat storage (particularly visceral belly fat), increases cravings for high-calorie foods, disrupts sleep, and impairs insulin sensitivity. Monitor your stress levels with our Stress Level Calculator.
Optimal Macros for Weight Loss
While total calories are the primary driver of weight change, the macro split significantly affects body composition, hunger, and energy during a deficit. For weight loss, we recommend approximately 35% protein, 35% carbohydrates, and 30% fat. Here is the scientific rationale:
- High protein (35%): Protein is the most satiating macronutrient -- it reduces hunger hormones and increases satiety hormones more than carbohydrates or fat. Critically, it preserves muscle mass during a deficit. Aim for 1.6-2.2g per kg of your target body weight daily. High protein also has a higher thermic effect (20-30% of its calories are burned in digestion vs 5-10% for carbs and fat).
- Moderate carbohydrates (35%): Carbohydrates support training performance and mood. Cutting carbohydrates too low impairs high-intensity exercise, reduces thyroid hormone output, and can cause fatigue and irritability. Low-carb diets work but are not superior to higher-carb approaches when protein and total calories are matched.
- Moderate fat (30%): Fat is essential for hormone production, including testosterone and oestrogen. Never cut fat below 20% of total calories as this impairs hormonal health and fat-soluble vitamin absorption (A, D, E, K). Check your Vitamin D status with our Vitamin D Calculator as deficiency is associated with impaired weight loss.
Exercise vs Diet for Weight Loss -- What the Research Shows
Diet is responsible for approximately 80% of weight loss results -- it is simply easier to reduce 500 calories through eating less than to burn 500 calories through exercise. However, exercise is critical for how you lose weight, not just whether you lose it.
Resistance training (strength training) during a calorie deficit preserves or even builds muscle mass, dramatically improving body composition outcomes. Two people with the same total weight loss can look very different -- one losing primarily fat while the other loses a mixture of fat and muscle. Use our Calories Burned Calculator to understand the exercise component of your energy balance.
The optimal approach is: moderate calorie deficit + high protein + resistance training 3-4 times per week + 8,000-10,000 daily steps (use our Steps to Calories Calculator). This combination produces the best body composition outcomes, the most sustainable results, and the lowest risk of weight regain.
Top 8 Evidence-Based Weight Loss Tips
- Weigh yourself weekly, not daily: Daily weight fluctuates by 1-3 kg due to water retention, food volume, and hormonal changes. Weekly weigh-ins (same day, same time, before eating) give a more accurate trend line.
- Eat protein at every meal: Protein takes longer to digest and has stronger satiety effects than carbohydrates or fats. Starting meals with protein naturally reduces total calorie intake.
- Drink water before meals: Drinking 500ml of water 30 minutes before meals reduces calorie intake by approximately 13% in research. Use our Water Intake Calculator for your daily target.
- Sleep 7-9 hours: Poor sleep increases hunger hormones and makes calorie deficits much harder to maintain. Use our Sleep Calculator to find your ideal wake-up time.
- Reduce ultra-processed foods: Ultra-processed foods are engineered to be hyper-palatable and easy to overeat. A 2019 NIH study found people eating ultra-processed diets consumed 508 more calories per day than those eating minimally processed foods -- even when both groups had the same food available.
- Track your food intake: Research consistently shows that people who track their food lose more weight than those who do not, primarily by increasing awareness and preventing the unconscious underestimation of intake that affects most people.
- Manage stress: Chronic stress raises cortisol and drives emotional eating. Assess your stress level with our Stress Level Calculator.
- Monitor your blood pressure: Weight loss has a dramatic effect on blood pressure. Monitor yours with our Blood Pressure Checker to see the health benefits as you lose weight.
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