Calorie Deficit Calculator (Goal Weight by Date)
Enter your current weight, your goal weight, and how many days you have to get there, and this calculator works out the daily calorie deficit that timeline requires, the weekly rate of loss it implies, and whether that pace is sustainable. It uses the common 7,700 kcal-per-kilogram rule of thumb and flags plans that ask your body to lose weight faster than is generally considered safe. It is a planning estimate, not medical or nutrition advice.
Goal & timeline
Estimate only — not medical or nutrition advice. Pair the daily deficit with your maintenance calories (TDEE) to get an actual intake target.
Daily calorie deficit needed
550kcal/day
10.0 kg over 140 days · 0.50 kg/week
Weekly loss
0.50 kg
Total deficit
77,000
Deficit detail
Projected weight over the timeline
Compare scenarios
Run the same calculation with two or three input sets side by side. Differences are highlighted; every number comes from the same tested formula as the calculator above.
| Input | Scenario A | Scenario B |
|---|---|---|
| Current Kg | ||
| Goal Kg | ||
| Days |
How it works
First the calculator finds how much you want to lose (current weight − goal weight) and multiplies it by 7,700 — the approximate number of calories stored in a kilogram of body fat — to get the total energy deficit your goal represents. Dividing that total by the number of days you have gives the average daily calorie deficit. In the worked example built into the tool, losing 10 kg over 140 days is a 77,000 kcal total, or 550 kcal per day.
That daily deficit is then converted back into a weekly rate of weight loss: daily deficit × 7 ÷ 7,700. A 550 kcal/day deficit works out to roughly 0.5 kg per week. Seeing the weekly figure matters because sustainable fat loss is usually described in kilograms or pounds per week, not in raw calorie numbers, and it makes an unrealistic timeline obvious at a glance.
Finally the plan is checked against a safe-loss ceiling — the stricter of 1% of your body weight or about 1 kg per week, which lines up with the widely cited guidance of 0.5–1 kg (roughly 1–2 lb) per week. If your timeline demands a faster loss than that, the tool shows an aggressive-deficit warning. The projected-weight chart draws a straight glide path from today's weight down to your goal on the target date so you can see the trajectory the numbers describe.
Frequently asked questions
Is the 7,700 kcal per kilogram rule exact?+
No — it is an approximation, not a physical constant. The '3,500 kcal per pound' (about 7,700 kcal per kilogram) figure comes from the rough energy content of stored body fat, but real weight change also involves water, glycogen, and lean tissue, and your metabolism adapts as you lose weight. In practice actual loss tends to slow over time, so treat the daily deficit here as a starting target and adjust based on how your weight actually trends over 2–4 weeks. Research tools like the NIH Body Weight Planner model these dynamics more precisely than a flat 7,700 figure can.
Why does it warn me when my deficit is too aggressive?+
Very large deficits and very fast weight loss carry real downsides: greater loss of muscle rather than fat, higher risk of nutrient shortfalls, fatigue, and a plan that is hard to stick to. The calculator flags any timeline that requires losing more than the stricter of 1% of your body weight or about 1 kg per week, which aligns with the CDC's guidance that a gradual 1–2 lb (roughly 0.5–1 kg) per week is more likely to stay off. If you see the warning, the usual fix is to extend your target date rather than cut calories harder.
Should I pair this with a TDEE calculator, and is this medical advice?+
Yes to the first, no to the second. This tool tells you the size of the deficit you need, but not the calorie intake that produces it — for that you need your maintenance calories (TDEE). Subtract the daily deficit here from your TDEE to get an actual daily calorie target, and never drop to an intake that leaves you under-nourished. This calculator is an educational estimate, not medical, nutrition, or clinical advice. If you have a health condition, are pregnant, or have any history of disordered eating, talk to a doctor or registered dietitian before starting a deficit.