Calorie deficit calculator
Enter your profile and your target weight: the calculator estimates your maintenance calories, then the daily intake for four deficit intensities, the weekly loss each one implies, and how long the goal would take.
About 30 seconds
The formulas used
Basal metabolic rate (Mifflin-St Jeor) = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, − 161 for women.
Maintenance calories = basal metabolic rate × activity factor (1.2 sedentary; 1.375 lightly active; 1.55 active; 1.725 very active; 1.9 extremely active) — the same factors as the TDEE calculator on this site.
Target intake = maintenance × (1 − deficit intensity). Weekly loss = daily deficit × 7 ÷ 7,700, 7,700 kcal being the energy held in one kilo of body mass.
With maintenance calories of 2,594 kcal a day, a 15% deficit means an intake of 2,205 kcal a day — 389 kcal less every day, or about 0.35 kg a week.
Equation from Mifflin M. D. et al. (American Journal of Clinical Nutrition, 1990); the 7,700 kcal per kilo equivalence comes from Wishnofsky (1958). That equivalence over-states long-term loss, because expenditure falls as body weight does.
The four intensities, at 2,594 kcal of maintenance
| Intensity | Daily intake | Weekly loss | Estimated time |
|---|---|---|---|
| Gentle (−10%) | 2,335 kcal/day | 0.24 kg/week | — |
| Moderate (−15%) | 2,205 kcal/day | 0.35 kg/week | — |
| Sustained (−20%) | 2,075 kcal/day | 0.47 kg/week | — |
| Aggressive (−25%) | 1,946 kcal/day | 0.59 kg/week | — |
How low to go, and no lower
Below roughly 1,200 kcal a day for women and 1,500 kcal for men, covering protein, fibre, vitamins and minerals becomes very hard. An intake that low belongs with a doctor or a dietitian, not a calculator.
A useful ceiling: no more than about 1% of body weight lost per week. Beyond that, more of the loss comes from muscle, and regaining the weight afterwards becomes more likely.
A deficit is not a straight line. Metabolism adapts, spontaneous movement drops, and the rate slows after a few weeks. Maintenance breaks of 7 to 14 days every 6 to 12 weeks make the whole thing easier to sustain.
Using it in practice
Hold the intake for two to three weeks, weigh yourself under the same conditions and read the weekly average rather than a single number: water shifts easily hide a kilo.
Keep protein high (roughly 1.6 to 2.2 g per kilo of body weight) and keep lifting: that is what protects muscle while you lose.
If the loss stalls for more than three weeks, adjust by 100 to 200 kcal or add activity rather than cutting sharply — this calculator gives a starting point, not a fixed plan, and it is no substitute for medical advice.
Work out my TDEE first · Estimate the calories I burn training · See all calculators
Frequently asked questions
Here are some common questions about working out a calorie deficit.
Losing 1 kg a week takes a deficit of about 1,100 kcal a day (7,700 ÷ 7). For most profiles that is well over 25% of maintenance, a pace that only makes sense at the very start and for the heaviest people. Half a kilo a week is far easier to hold.
There is no universal number: everything starts from your maintenance calories, which depend on your weight, height, age, sex and activity. A deficit of 10 to 20% below maintenance suits the vast majority of situations.
Not without supervision. Below 1,200 kcal for women and 1,500 kcal for men, protein and micronutrient needs become hard to cover. If your maintenance is low, raise your expenditure rather than dropping the intake further.
Because a lighter body burns less, and because the body trims its spontaneous expenditure in response to the deficit. Recalculate your maintenance every 4 to 5 kg lost, and expect the pace to ease off: that is normal physiology, not failure.
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