How the Weight Loss Calculator Works

One kilogram of body fat stores about 7,700 calories (one pound is about 3,500). Fat loss is just the total deficit divided by that number. Everything this tool does comes from one formula, used in two directions.

Find the deficit you need

daily deficit = (kg to lose × 7,700) / (weeks × 7). Set a goal and a deadline, and it returns the average daily deficit required. Example: 10 kg in 22 weeks needs roughly a 500 cal/day deficit.

Find how long it takes

weeks = (kg to lose × 7,700) / (daily deficit × 7). Set a deficit you can actually sustain and it returns the timeline. Example: 10 kg at a 500 cal/day deficit takes about 22 weeks.

Keep it sustainable

The safe range is 0.5 to 1% of bodyweight per week. Add your current bodyweight and the calculator checks your rate against that range. Faster than 1% per week and your body breaks down muscle along with fat. Pair any deficit with 1.6 to 2.2 g of protein per kg of bodyweight to keep the loss as fat.

For the realistic timelines, why progress stalls, and how to adjust as you lean out, read the full article: Weight Loss Calculator: How Long It Takes to Hit Your Goal.