Weight Loss Calculator — How Long to Reach Your Goal Weight
Calculate how long it'll take to reach your target weight based on your calorie deficit. Set realistic timelines with TDEE, deficit size, and weekly targets.
Weight loss math is simple: eat fewer calories than you burn, consistently, over time. The CalcHub Weight Loss Calculator tells you exactly how long it will take to reach your goal weight based on your calorie deficit — and why crash diets don't work mathematically.
The Core Formula
1 kg of body fat ≈ 7,700 caloriesTo lose 1 kg per week, you need a daily deficit of approximately 1,100 calories. To lose 0.5 kg per week (the more sustainable target), you need a 550-calorie daily deficit.
Weight Loss Timeline
Starting weight: 85 kg, goal: 72 kg (lose 13 kg)| Daily Deficit | Weekly Loss | Time to Goal | Daily Calories (TDEE 2,500) |
|---|---|---|---|
| 250 cal | 0.23 kg | ~56 weeks (13 months) | 2,250 |
| 500 cal | 0.45 kg | ~29 weeks (7 months) | 2,000 |
| 750 cal | 0.68 kg | ~19 weeks (4.5 months) | 1,750 |
| 1,000 cal | 0.91 kg | ~14 weeks (3.5 months) | 1,500 |
Step 1: Find Your TDEE
TDEE (Total Daily Energy Expenditure) = how many calories you burn daily including activity.
| Activity Level | Multiplier | Example (BMR 1,800) |
|---|---|---|
| Sedentary (desk job, no exercise) | × 1.2 | 2,160 cal |
| Lightly active (1–3 days exercise/week) | × 1.375 | 2,475 cal |
| Moderately active (3–5 days/week) | × 1.55 | 2,790 cal |
| Very active (6–7 days/week) | × 1.725 | 3,105 cal |
Step 2: Set Your Deficit
| Your Goal | Recommended Deficit | Expected Weekly Loss |
|---|---|---|
| Slow and steady | 250–300 cal/day | 0.2–0.3 kg/week |
| Standard weight loss | 500 cal/day | 0.45 kg/week |
| Aggressive (short-term) | 750 cal/day | 0.7 kg/week |
| Maximum safe rate | 1,000 cal/day | 0.9 kg/week |
Step 3: Set Realistic Expectations
Weight loss is never linear. Here's what actually happens:
Week 1–2: Fast loss (2–3 kg) — mostly water weight, not fat. Don't get excited. Week 3–8: Steady loss (0.3–0.5 kg/week) — this is actual fat loss. This is the real pace. Week 8–16: Possible plateau — your TDEE decreases as you weigh less. Recalculate. Beyond 16 weeks: May need to adjust. Metabolism adapts, activity naturally decreases, and hunger signals increase. This is normal, not failure.Why Crash Diets Fail (The Math)
A "lose 10 kg in 30 days" diet requires a daily deficit of ~2,567 calories. For someone with a TDEE of 2,500, that means eating negative 67 calories per day — literally impossible without complete starvation.
Even eating nothing (0 calories) would only create a 2,500-calorie deficit, producing ~9.7 kg loss in 30 days — but most of that would be muscle and water, not fat. You'd regain it within weeks.
Safe Weight Loss Rate by Starting Weight
| Starting BMI | Recommended Weekly Loss | Monthly Loss |
|---|---|---|
| 25–27 (slightly overweight) | 0.25–0.5 kg | 1–2 kg |
| 27–30 (overweight) | 0.5–0.75 kg | 2–3 kg |
| 30–35 (obese) | 0.5–1 kg | 2–4 kg |
| 35+ (severely obese) | 0.75–1.5 kg | 3–6 kg |
How to Use the Calculator
- Open the CalcHub Weight Loss Calculator
- Enter current weight and goal weight
- Enter your TDEE (or calculate it in the tool)
- Choose your daily calorie intake
- See: time to reach goal, weekly loss rate, and milestone dates
Why has my weight loss stalled?
Three common reasons: (1) Your TDEE has decreased because you weigh less now — recalculate and adjust. (2) You're eating more than you think — track calories strictly for a week. (3) You're retaining water from exercise, stress, or hormonal changes — weight fluctuates ±1–2 kg daily, look at weekly averages instead of daily numbers.
Should I focus on diet or exercise for weight loss?
Diet creates the deficit; exercise supports it. It's far easier to eat 500 fewer calories than to burn 500 extra through exercise (that's ~60 minutes of running). The most effective approach: create 70% of your deficit through diet, 30% through exercise.
How much muscle will I lose while losing weight?
Without strength training, about 25% of weight lost will be muscle. With regular strength training and adequate protein (1.6–2.2g/kg), you can reduce muscle loss to under 10%. This is why resistance training during weight loss is critical — not just for body composition, but for maintaining metabolic rate.
Related Calculators
- Calorie Calculator — daily calorie needs
- BMI Calculator — where you stand
- Body Fat Calculator — body composition beyond weight
- Macro Calculator — protein, carbs, fat targets