What this calculator does
This weight loss calculator by date starts from your current weight, a goal weight and a target date, and works backwards to the weekly rate of loss and daily calorie deficit that would be needed to get there by then. That is the reverse of the site’s calorie deficit calculator, which starts from a chosen rate and works out the resulting calories, not a date.
The two calculators share the same underlying energy-balance maths (roughly 7,700 kcal of deficit per kilogram of fat lost), but this one is framed around a deadline rather than a rate you pick yourself. Because a fixed date can imply an unrealistic pace, the result also flags when the required rate looks faster than is commonly considered sustainable.
The formula
The number of weeks between today and the target date is the time available. Dividing the total weight to lose (current weight minus goal weight) by that number of weeks gives the required weekly rate, and converting that weekly rate to a daily calorie deficit uses the same 7,700 kcal per kilogram figure used elsewhere on the site.
| Term | Meaning |
|---|---|
| Weeks available | (target date − today) ÷ 7, rounded to the nearest tenth of a week. |
| Required weekly rate | (current weight − goal weight) ÷ weeks available. |
| Daily calorie deficit | Required weekly rate (kg) × 7,700 kcal ÷ 7 days. |
The inputs explained
| Field | What to enter |
|---|---|
| Current weight (kg) | Your current weight. |
| Goal weight (kg) | The weight you are aiming for. This must be lower than your current weight, since this calculator only works out a required rate of loss. |
| Target date | The date you want to reach that goal weight by. |
When to use it
Checking whether a deadline is realistic
Before committing to a specific date, such as an event or a holiday, working out the implied weekly rate shows whether that timeline is a sensible pace or an unrealistically fast one.
Choosing between a shorter and a longer timeline
Running the same start and goal weight against two different target dates shows directly how much easier a slower, longer timeline is on the required daily deficit.
Translating a goal into a daily target
A date and a goal weight on their own do not say what to do today; converting them into a daily calorie deficit gives a concrete number to plan meals and activity around.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the required weekly rate changes with more or less time
A fixed 7 kg to lose, across a range of target dates expressed in weeks from today.
| Target date | Required weekly weight loss | Required daily calorie deficit |
|---|---|---|
| 28 days out | 1.75 kg/week | 1,925 kcal/day |
| 42 days out | 1.17 kg/week | 1,283 kcal/day |
| 56 days out | 0.88 kg/week | 963 kcal/day |
| 84 days out | 0.58 kg/week | 642 kcal/day |
| 112 days out | 0.44 kg/week | 481 kcal/day |
| 168 days out | 0.29 kg/week | 321 kcal/day |
How the daily deficit changes with a bigger or smaller goal
A fixed 84-day timeline, across a range of total amounts to lose.
| Goal weight (from 90 kg) | Total weight to lose | Required daily calorie deficit |
|---|---|---|
| 85 kg | 5.00 kg | 458 kcal/day |
| 82 kg | 8.00 kg | 733 kcal/day |
| 78 kg | 12.00 kg | 1,100 kcal/day |
| 74 kg | 16.00 kg | 1,467 kcal/day |
| 70 kg | 20.00 kg | 1,833 kcal/day |
| 65 kg | 25.00 kg | 2,292 kcal/day |
Questions
What counts as a sustainable rate of weight loss?
Roughly 0.5 to 1 kg a week is a commonly cited range for sustainable, largely fat-based weight loss. This calculator uses 1 kg a week as the upper bound before flagging a required rate as potentially unrealistic, but individual circumstances vary and a doctor or dietitian is the right source for personal guidance.
What should I do if my required rate comes back too fast?
The two levers available are extending the target date or choosing a less ambitious goal weight; either one lowers the required weekly rate. The calculator’s guide message suggests this directly rather than presenting a fast timeline as achievable.
How is this different from the calorie deficit calculator?
The calorie deficit calculator starts from a weekly rate you choose and works out the resulting daily calorie target. This calculator works the other way: it starts from a deadline and a goal weight and works out what rate, and what daily deficit, that deadline actually implies.
Does this calculator account for muscle loss or metabolic slowdown?
No. It is a simple energy-balance estimate based on a fixed kcal-per-kilogram figure, and does not model changes in metabolic rate, muscle loss, or water-weight fluctuations that occur in practice over a real weight-loss period.
To convert a chosen rate into a daily calorie target directly, see the calorie deficit calculator. For a broader picture of energy needs, see the BMI calculator.