Weight Loss Calculator
How it works
Each kg of fat stores ~7,700 kcal. Multiply your weekly target loss by 7,700 to get the weekly calorie deficit, divide by 7 for daily. Subtract from your TDEE to get your daily eating target.
Worked example
85 kg → 75 kg in 20 weeks (TDEE 2,200):
- 10 kg ÷ 20 = 0.5 kg/week (safe)
- 3,850 ÷ 7 = 550 kcal/day deficit
- 2,200 − 550 = 1,650 kcal/day target
Who should use this
- •Anyone planning a weight-loss target
- •People wanting realistic timelines
- •Pre-bariatric or weight-management programme participants
Common mistakes
- ×Setting too aggressive a timeline (1 kg/week+)
- ×Forgetting to recalculate as you lose weight (TDEE drops too)
- ×Crash dieting — loses muscle and rebounds quickly
- ×Skipping strength training — keeps fat-loss but loses muscle
Frequently asked questions
How fast can I safely lose weight?▾
0.5-1 kg per week is the NHS recommendation. Faster is rarely sustainable and risks muscle loss.
Why have I plateaued?▾
Your TDEE drops as you lose weight (lower mass to maintain) plus 'adaptive thermogenesis'. Re-calculate every 4-6 kg lost.
Should I exercise to create the deficit or eat less?▾
Both work. Exercise (especially strength) preserves muscle, but most of the deficit usually comes from food — it's easier to eat 500 fewer kcal than burn 500.
Is fasting better?▾
Intermittent fasting is one approach to eating in a deficit; total calories matter most. Time-restricted eating helps some people stick to a deficit.