Calorie Deficit Calculator

Use your current weight from a morning weigh-in and a goal that is below it. The tool plans weight loss only: if the goal is not below the current weight it asks you to use the calorie calculator instead.

1. Choose your Sex and set Units to Metric (cm, kg) or Imperial (ft, in, lb).
2. Enter your Age. In metric, type Height (cm). In imperial, type Height (feet) and Height (inches) instead.
3. Enter your current weight in the weight box, which is labeled Weight (kg) or Weight (lb), and your Goal weight (kg or lb). After you switch units, retype both weights, since the fields keep the numbers already there.
4. Pick your Activity level, from little or no exercise (1.2) up to very hard exercise or a physical job (1.9).
5. Choose a Daily deficit: 250 kcal (gentle), 500 kcal (standard), 750 kcal (fast) or 1,000 kcal (aggressive).
6. Read the daily target, the maintenance calories, the expected weekly loss and the two timelines.

The tool first estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation: 10 x kg + 6.25 x cm - 5 x age + 5 for men, or - 161 instead of + 5 for women. Multiplying by the activity factor gives maintenance calories, also called TDEE. The daily target is maintenance minus the deficit. A body-weight change of about 7,700 kcal per kg (3,500 per lb) converts the deficit into weeks.

Take a man aged 35, 172 cm tall, 85 kg, with a goal of 75 kg and light exercise (1.375). His BMR is 850 + 1,075 - 175 + 5 = 1,755 kcal. Maintenance is 1,755 x 1.375 = 2,413 kcal, so a 500 kcal deficit gives a target of 1,913 kcal a day. The expected loss is 500 x 7 / 7,700, about 0.5 kg a week. To lose 10 kg the simple estimate is 22 weeks.

The adjusted estimate is longer, about 26 weeks, because maintenance falls as you get lighter and the real deficit shrinks. The tool recalculates every week and lists milestones:

For the four deficit choices, the starting weekly loss is about 0.23 kg (0.5 lb) for 250 kcal, 0.45 kg (1 lb) for 500, 0.68 kg (1.5 lb) for 750 and 0.91 kg (2 lb) for 1,000.

The tool shows a warning when the target falls below about 1,500 kcal for men or 1,200 kcal for women, and another when the weekly loss is more than 1 percent of body weight. Both can appear together. A woman aged 40, 5 ft 5 in, 180 lb, with a goal of 150 lb, little exercise and a 1,000 kcal deficit has maintenance near 1,785 kcal, so the target is 785 kcal and both warnings appear. A smaller deficit is the usual fix, and the tool suggests it. Choosing 250 or 500 kcal keeps the target higher and the weekly loss closer to the 0.5 to 1 percent of body weight range that the warning refers to.

One more limit: the calculator does not read your food log. A calorie target is only a number until it is compared with what you actually eat, and package labels and restaurant menus are themselves approximate.

Every figure is a population average. Your real metabolism can differ by a couple of hundred calories, water weight moves the scale from day to day, and losing weight is not perfectly linear. Treat the weeks as a rough planning range and adjust from your own results. Weigh yourself at the same time of day, compare weekly averages and not single mornings, and recheck the numbers after a large change in weight, because the target moves as maintenance does. If you gain nothing and lose nothing for several weeks, your maintenance is probably different from the estimate, not your willpower.

This is an estimate for general information and not medical advice. People with a health condition, who are pregnant or who are under 18 should talk to a doctor or dietitian before changing how they eat. The calorie calculator handles maintenance and weight gain, and the macro calculator splits a calorie figure into protein, carbs and fat. Check where you start with the BMI calculator or the ideal weight calculator, and use the pounds to kilograms converter to compare weights across units.