Free calculator

Weight Loss Calculator

See exactly how long it will take to reach your goal weight with a personalised week-by-week projection. Enter your current stats and goal, and this calculator maps out your weight loss timeline with the daily calorie target needed.

Enter your details

Gender

Age

years

Current Weight

Height

Activity Level

Goal Weight

Weekly Loss Rate

Your Weight Loss Timeline

Example

Example figures, not your own. Worked for a lightly active 35 year old woman of 85 kg and 165 cm losing 0.5 kg a week to 70 kg. Enter your own details and press Calculate.

Starting Daily Target

6,590kJ/day

2,301 kJ daily deficit

Estimated Time to Goal

30weeks

7 months to reach 70 kg

Weekly Loss Rate

0.5kg/week

Sustainable rate

Week-by-Week Projection

Week	Weight	TDEE	Daily Target
Start	85 kg	8,891 kJ	6,590 kJ
Week 4	83 kg	8,774 kJ	6,473 kJ
Week 8	81 kg	8,657 kJ	6,355 kJ
Week 12	79 kg	8,540 kJ	6,238 kJ
Week 16	77 kg	8,422 kJ	6,121 kJ
Week 20	75 kg	8,305 kJ	6,004 kJ
Week 24	73 kg	8,188 kJ	5,887 kJ
Week 28	71 kg	8,071 kJ	5,770 kJ
Week 29	70.5 kg	8,042 kJ	5,740 kJ
Week 30	70 kg	8,025 kJ	5,724 kJ

How It Works

The calculator estimates your TDEE using the Mifflin-St Jeor equation, then applies your chosen weekly loss rate to determine the required daily deficit. Since 1 kg of body fat contains approximately 7,700 kcal (32,200 kJ), the daily deficit needed is (weekly loss in kg × 7,700) ÷ 7. The timeline accounts for decreasing TDEE as your weight drops by recalculating at each projected week.

How to use it

1Enter your gender, age, current weight (kg), and height (cm)
2Select your activity level
3Enter your goal weight in kilograms
4Choose your preferred weekly loss rate (0.25, 0.5, 0.75, or 1.0 kg/week)
5Click "Calculate" to see your timeline and weekly milestones

Quick Reference

Weekly Rate	Daily Deficit	Time to Lose 5 kg	Time to Lose 10 kg	Time to Lose 20 kg
0.25 kg/wk	1,150 kJ (275 kcal)	20 weeks	40 weeks	80 weeks
0.5 kg/wk	2,300 kJ (550 kcal)	10 weeks	20 weeks	40 weeks
0.75 kg/wk	3,450 kJ (825 kcal)	7 weeks	14 weeks	27 weeks
1.0 kg/wk	4,600 kJ (1,100 kcal)	5 weeks	10 weeks	20 weeks

Approximate timelines assuming constant deficit. In practice, progress slows as weight decreases. This calculator accounts for that.

How This Is Calculated

Daily Deficit (kcal) = (Weekly Loss Rate × 7,700) ÷ 7 Target Intake = TDEE − Daily Deficit Weeks to Goal = Total Loss ÷ Weekly Loss Rate Note: TDEE is recalculated each week as weight drops

7,700: = Approximate kcal per kg of body fat
TDEE: = Total Daily Energy Expenditure, recalculated weekly
Weekly Loss Rate: = Chosen rate: 0.25, 0.5, 0.75, or 1.0 kg/week

The projection recalculates your TDEE each week as your weight drops, providing a more realistic timeline than simple linear projections.

Frequently Asked Questions

How fast should I lose weight?

The NHMRC and most Australian health guidelines recommend losing 0.5-1.0 kg per week. Faster rates increase the risk of muscle loss, gallstones, and nutrient deficiencies. A rate of 0.5 kg per week (requiring a 500 kcal daily deficit) is sustainable for most people.

Why does the timeline account for slowing progress?

As you lose weight, your body becomes smaller and burns fewer kilojoules each day. This means the same calorie deficit produces less weight loss over time. Our calculator recalculates your TDEE at each projected week to give a realistic, not overly optimistic, timeline.

Is it harder to lose the last few kilograms?

Yes. As you get closer to your goal weight, your BMR and TDEE decrease, making the same deficit harder to maintain. Your body also tends to resist further fat loss through increased hunger hormones and reduced non-exercise activity. Patience and consistency are key during this phase.

What if I want to lose weight faster than 1 kg per week?

Losing more than 1 kg per week requires a large calorie deficit that is difficult to sustain and can lead to muscle loss, fatigue, and nutritional deficiencies. Very low calorie diets (VLCDs) of 1,800-3,400 kJ per day should only be followed under medical supervision.

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