Weight Loss Timeline Calculator

Current weight, kg

Target weight, kg

Daily calorie deficit

Maintenance calories a day

Result

Weeks26.4
In months6.1
Kg a week0.455
Kg a month1.98
Eat a day, kcal1,900
Rate assessmenta 21% deficit, which is within safe limits

This result is informational only and is not professional advice.

A kilogram of fat is 7,700 kilocalories

Works out how many weeks a weight target takes at a chosen calorie deficit, and whether the rate is safe.

All the arithmetic of weight loss rests on one number: a kilogram of body fat is worth about 7,700 kilocalories. A 500 kcal daily deficit is 3,500 a week, or roughly 450 grams. No diet gets around that balance.

Which explains the disappointment that follows quick results: the first kilograms are water and glycogen rather than fat, so week one always beats the calculation and weeks two and three fall behind it.

What this calculator shows

How many weeks and months the target takes
The rate of loss per week and per month
What to eat daily, and whether the deficit is too aggressive

What to keep in mind

The model is linear: it ignores the fact that maintenance calories fall as weight does, so the real timeline runs slightly longer.
A deficit above a quarter of maintenance counts as aggressive; at that level muscle is noticeably lost alongside fat.

FAQs

How much can I safely lose in a week?

Half to one percent of bodyweight: for someone at 90 kilograms that is 450 to 900 grams. Faster comes out of muscle.

Why has my weight stalled on a deficit?

Usually water retention masking fat loss for weeks at a time. Read the month-long trend rather than daily readings.

Where does 7,700 come from?

From the energy content of adipose tissue: pure fat is about 9,000 kcal per kilogram, but the tissue also holds water and protein, so 7,700 is the working figure.

Should maintenance be recalculated along the way?

Yes. Every five kilograms lost drops maintenance by roughly a hundred kilocalories, and without adjusting, the loss gradually stalls.

Worked example

Twelve kilograms

Input: 90 kg down to 78, a 500 kcal deficit against 2,400 maintenance

Output: 26 weeks at about 455 g a week

Note: Half a year for twelve kilograms is a realistic figure that rarely appears in advertising. The deficit here is 21 percent of maintenance, safely within limits.

Useful links

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Weight Loss Timeline Calculator

Result

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