How it is calculated
- We estimate your daily needs (TDEE) with Mifflin-St Jeor and an activity factor.
- A kilogram of fat is about 7,700 kcal, so losing 0.5 kg a week needs a daily deficit of about 550 kcal.
- Time = (current − goal) ÷ weekly loss, recalculating TDEE as weight falls since needs drop.
A safe pace is usually 0.25–1% of body weight per week.
Worked example
A 90 kg man aiming for 80 kg at 0.5 kg a week needs about 20 weeks (around 5 months), eating roughly 2,300 kcal a day at first if moderately active.
Frequently asked questions
Why does weight loss slow down?
A lighter body needs fewer calories, so the deficit shrinks unless you adjust; the calculator accounts for this.
Is a bigger deficit faster?
Very large deficits cause muscle loss and fatigue and are hard to sustain.
Do I need exercise?
Not strictly for weight loss, but it preserves muscle and improves health; resistance training helps a lot.