Calorie Deficit Calculator: calories a day to lose weight

Find how many calories a day to eat to lose weight at the rate you choose, how big your calorie deficit is, and when you'll reach your goal weight. Metric or US units.

Compare rates to reach 65 kg
Lose a week	Eat (kcal a day)	Deficit	Time
0.25 kg	1,643	276	20 weeks
0.5 kg	1,367	551	10 weeks
0.75 kg	1,092 ⚠	827	6 weeks 5 days
1 kg	816 ⚠	1,102	5 weeks

How the calorie deficit calculator works

It estimates your maintenance calories (TDEE): your BMR from the Mifflin–St Jeor equation, times an activity factor from 1.2 (desk job) to 1.9 (hard training).
It turns your weekly goal into a daily deficit. About 3,500 calories make up a pound of weight lost, so 1 lb a week is 500 calories a day, and 0.5 kg a week is 551.
Calories a day = maintenance calories − deficit. Time to your goal = weight to lose ÷ weekly rate.
Because a lighter body burns less, it also shows what you'd eat at your goal weight to keep the same pace.

Worked example

A 35-year-old woman, 165 cm and 70 kg, lightly active, wants to reach 65 kg at 0.5 kg a week. Her BMR is 700 + 1,031.25 − 175 − 161 = 1,395 kcal, × 1.375 = 1,918 kcal maintenance. A 0.5 kg weekly loss needs a 551 kcal daily deficit, so she eats about 1,367 kcal a day, and 5 kg ÷ 0.5 kg = 10 weeks. By 65 kg her maintenance drops to 1,850 kcal, so keeping the same pace means about 1,299 kcal a day.

A safe rate of weight loss

The NHS advises aiming to lose 0.5 to 1 kg (1 to 2 lb) a week, and the CDC says people who lose about 1 to 2 lb a week are more likely to keep it off.
The calculator warns if your target falls below 1,200 calories a day for women or 1,500 for men, the lowest intakes in the US weight-loss guideline (AHA/ACC/TOS, 2013). Very low-calorie diets (under 800) need a doctor.
NIH research behind the Body Weight Planner shows weight loss slows over time if you keep eating the same amount, because your body needs less as it gets lighter. That's why the plan lowers your calories as you go.

Make it easier

Check your starting point with the maintenance calorie calculator and pick a realistic goal with the ideal weight calculator.
Protein helps you feel full and keep muscle while you lose fat: see how much with the protein calculator, and split the rest with the macro calculator.
Weigh yourself at the same time of day and look at the weekly average, not single days.

Sources, checked 2 October 2026: NHS, Overweight and obesity in adults and Calories and weight loss; CDC, Losing weight; NIH NHLBI, The Practical Guide to overweight and obesity in adults; Jensen MD et al., 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults; Hall KD et al., Quantification of the effect of energy imbalance on bodyweight, Lancet 2011;378:826–37; Mifflin MD, St Jeor ST et al., American Journal of Clinical Nutrition 1990;51:241–7. Not medical advice.

Frequently asked questions

What is a calorie deficit?

A calorie deficit means eating fewer calories than your body uses in a day (your maintenance calories, or TDEE). Your body makes up the gap from its stores, mostly fat, so your weight goes down over time.

How big a deficit do I need to lose 1 lb or 0.5 kg a week?

About 500 calories a day for 1 lb (0.45 kg) a week, and about 551 a day for 0.5 kg. That comes from the usual estimate of 3,500 calories per pound of weight lost, which the NIH uses when it says a deficit of 500 to 1,000 calories a day gives a loss of 1 to 2 pounds a week. The NHS suggests cutting about 600 calories a day.

Is a 1,000-calorie deficit safe?

A 1,000-calorie deficit is the top of the range in NIH guidance and gives about 2 lb (0.9 kg) a week. The NHS and CDC recommend losing 0.5 to 1 kg (1 to 2 lb) a week. Just as important, what's left to eat shouldn't fall below about 1,200 calories a day for women or 1,500 for men without medical supervision, so a big deficit only suits people with high maintenance calories.

Why am I not losing weight in a calorie deficit?

Formulas only estimate your maintenance calories, so your real deficit may be smaller than you think, and food is easy to under-count. Water also makes the scales jump around, so judge the trend over a few weeks. And as you get lighter you burn less, so a deficit that worked at the start shrinks. Recalculate with your new weight, and if nothing changes for a month, eat a little less or move more.

Should I add my exercise calories to the deficit?

No, not if you picked an activity level that includes your workouts: your maintenance calories already count them. Only if you chose 'Sedentary' and then exercise on top does that exercise add to your deficit.