How is the daily deficit calculated?

The weekly weight loss is multiplied by about 7700 kcal per kilogram, then divided by seven to give a daily figure.

Is the 7700 kcal per kilogram exact?

It's an approximation for body fat. Real results vary with water, muscle, and metabolism, so treat it as a guide.

What's a safe rate of loss?

Usually 0.5–1 kg per week. Faster needs large deficits that are harder to sustain and may reduce muscle.

Why does my loss slow down over time?

As you get lighter you burn fewer calories, so the same intake creates a smaller deficit. You may need to adjust.

Does it account for exercise?

The deficit can come from eating less, exercising more, or both. The calculator gives the total daily gap to create.

Can I share a calculation?

Yes. Use Share to copy a link that reopens the calculator with the same weights and timeframe.

Weight loss calculator

Enter your current weight, your goal weight, and how many weeks you have. The calculator shows the weekly loss, the total to lose, and the daily calorie deficit that rate implies.

Use it to turn a weight goal and a timeframe into a weekly rate and a daily calorie deficit.

Weekly loss

0.67 kg/week

Total to lose: 8 kg
Daily deficit: 733 kcal

The result updates as you type. The headline is the weekly loss; the deficit tells you how much to cut each day to hit it.

How does it work?

One kilogram of fat is treated as about 7700 kcal. A safe rate is usually 0.5–1 kg per week; faster targets need large deficits that are hard to sustain. This is general guidance, not medical advice.

Weight loss formula

\text{deficit} = \frac{(C - G)/w \times 7700}{7}

C: Current weight in kilograms.
G: Goal weight in kilograms.
w: Weeks to reach the goal.
deficit: Daily calorie deficit needed.

Losing 8 kg over 12 weeks is about 0.67 kg per week, which needs roughly a 733 kcal daily deficit (using 7700 kcal per kg).

Method & sources

One kilogram of body fat is treated as about 7700 kcal. The weekly rate is the total to lose divided by the weeks. The daily deficit spreads the weekly rate across seven days.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

Healthy weight loss — U.S. Centers for Disease Control and Prevention, verified 2026-06-10

How we calculate

One kilogram of body fat is treated as about 7700 kcal.
The weekly rate is the total to lose divided by the weeks.
The daily deficit spreads the weekly rate across seven days.
This is general guidance, not medical advice; 0.5–1 kg a week is a safe range.

Rounding

Weights are shown to one or two decimals and calories as whole numbers. The calculation uses full precision.

What this calculator does

Losing weight comes down to an energy deficit over time. This calculator divides the weight you want to lose by your timeframe to get a weekly rate, then converts that into the daily calorie deficit it requires, using about 7700 kcal per kilogram of fat.

How to use it

Enter your current weight.
Enter your goal weight.
Enter how many weeks you have.
Read the weekly loss and daily deficit.

A worked example

Losing 8 kg over 12 weeks is about 0.67 kg a week, which needs roughly a 733 kcal daily deficit — through eating less, moving more, or both.

Setting a safe pace

A rate of 0.5–1 kg a week is usually safe and sustainable. If the daily deficit looks very large, give yourself more weeks; aggressive deficits are hard to maintain and can cost muscle.

Common mistakes

Setting a timeframe so short the deficit is unrealistic.
Forgetting that weight loss slows as you get lighter.
Treating the estimate as exact — real loss varies week to week.

When it's useful

Planning a realistic weight-loss timeline, checking whether a goal is achievable, or working out the daily deficit to aim for.

FAQ

How is the daily deficit calculated?: The weekly weight loss is multiplied by about 7700 kcal per kilogram, then divided by seven to give a daily figure.
Is the 7700 kcal per kilogram exact?: It's an approximation for body fat. Real results vary with water, muscle, and metabolism, so treat it as a guide.
What's a safe rate of loss?: Usually 0.5–1 kg per week. Faster needs large deficits that are harder to sustain and may reduce muscle.
Why does my loss slow down over time?: As you get lighter you burn fewer calories, so the same intake creates a smaller deficit. You may need to adjust.
Does it account for exercise?: The deficit can come from eating less, exercising more, or both. The calculator gives the total daily gap to create.
Can I share a calculation?: Yes. Use Share to copy a link that reopens the calculator with the same weights and timeframe.

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