Calorie deficit calculator
A calorie deficit means eating a little less than your body uses. Enter your details, pick a gentle or moderate deficit and see the daily target, with a safe floor it will never go below.
Updated 21 October 2026. Sources named on the page.
- Pick gentle (300) or moderate (550) below your daily energy
- Held at 1,200 kcal for women or 1,500 kcal for men, never lower
- Answers in kcal and kJ, metric or imperial
- Adults 19 and over, and nothing you type is saved or sent
Work out your deficit
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The formula, the deficit sizes and worked examples
The target is your daily energy (TDEE) minus the deficit, rounded to 50 kcal. If the answer would be under the floor for your sex, the floor is shown and the page says so.
Deficit sizes offered
| Size | Daily change | Rule of thumb |
|---|---|---|
| Gentle | minus 300 kcal | a slower change |
| Moderate | minus 550 kcal | about 0.5 kg a week |
Worked examples
| Person and activity | Daily energy | Deficit | Target |
|---|---|---|---|
| Man, 30 y, 80 kg, 180 cm, moderately active (x1.55) | 2,759 kcal | minus 300 | 2,450 kcal (10,251 kJ) |
| Same man | 2,759 kcal | minus 550 | 2,200 kcal (9,205 kJ) |
| Woman, 50 y, 150 cm, 45 kg, mostly sitting | about 1,100 kcal | minus 550 | Held at 1,200 kcal (5,021 kJ) |
Sources: Mifflin MD, St Jeor ST and others, American Journal of Clinical Nutrition, 1990, for resting energy; The activity factors and the 0.5 kg a week rule of thumb for about 550 kcal a day are commonly used estimates, not measurements of any person; 1 kcal = 4.184 kJ
Figures and sources checked 21 October 2026. General information, not medical advice.
Gentle or moderate: which to pick
A 300 kcal deficit is a smaller step that many people find easier to live with, and it suits you if you are already light, very active or new to this. A 550 kcal deficit is the larger of the two offered here and fits a rule of thumb of about 0.5 kg a week. Neither is better in itself: the one you can keep up for weeks is the right one.
What a deficit does not tell you
The calculator shows a number for eating. It cannot tell you how hungry you will be, how well you will sleep or whether your weight will fall in a straight line. Water, salt and the time of the month can move the scale by a kilogram or more in a day.
If the scale stops moving
Weight often pauses for a week or two. Before cutting further, check that portions and activity are as you think, and give it a few weeks. The floor still applies: do not go below the minimum shown, and speak to a doctor or dietitian if you feel unwell.
Questions
What is a calorie deficit?
It is eating fewer calories than your body uses in a day. Your body's use is your total daily energy expenditure, which this calculator estimates for you.
Why only two deficit sizes?
Gentle (300 kcal) and moderate (550 kcal) are modest sizes for healthy adults. Larger deficits are not offered because they are not appropriate without medical supervision.
Why does it say held at a minimum?
If the sum would land below 1,200 kcal for women or 1,500 kcal for men, the calculator holds the target at that floor instead.
How fast will I lose weight?
A common rule of thumb is about 0.5 kg a week for 550 kcal a day, but it is only a rule of thumb. Real results vary, and this is not a promise of any result.
Is a deficit suitable for me?
Only if you are a healthy adult aged 19 or over. It is not for pregnancy, breastfeeding or medical conditions. If you have or have had an eating disorder, please speak to a doctor or dietitian rather than use any calculator.
Keep going
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