How to use this calculator
Choose US or metric units, then enter your sex, age, height, weight and typical activity level. Pick a goal: lose 2, 1 or 0.5 lb a week, maintain, or gain 0.5 or 1 lb a week. The result updates as you type and shows:
- your daily calorie target for the goal you picked
- your maintenance calories, also called total daily energy expenditure (TDEE)
- your basal metabolic rate (BMR), the calories you’d burn lying still all day
- a table with every goal, flagging any target below the commonly cited minimum
- the working, step by step
If you’d like the target split into protein, carbs and fat, take it to the macro calculator. If you have a specific goal weight and date in mind, the calorie deficit calculator works backward from them.
The formula
The calculator works in three steps. First it estimates your BMR with the Mifflin-St Jeor equation (1990), using weight in kilograms, height in centimeters and age in years:
where s is +5 for men and −161 for women. Next it multiplies BMR by an activity factor to get maintenance calories:
The factors are the conventional ones used by most calorie calculators: 1.2 (sedentary), 1.375 (light exercise 1–3 days a week), 1.55 (moderate, 3–5 days), 1.725 (very active, 6–7 days) and 1.9 (extra active). Finally, it adds or subtracts calories for your goal, using the rule of thumb that a pound of body weight is about 3,500 calories. Losing 1 lb a week means a deficit of 3,500 ÷ 7 = 500 calories a day.
Worked example
Take a 35-year-old woman who is 5 ft 5 in (165.1 cm) and 160 lb (72.6 kg), lightly active, who wants to lose 1 lb a week.
- BMR: 10 × 72.6 + 6.25 × 165.1 − 5 × 35 − 161 = 1,422 calories
- Maintenance: 1,422 × 1.375 = 1,955 calories
- Target: 1,955 − 500 = 1,455 calories a day
Her full table looks like this:
| Goal | Calories a day |
|---|---|
| Lose 2 lb a week | 955 (below the 1,200 minimum) |
| Lose 1 lb a week | 1,455 |
| Lose 0.5 lb a week | 1,705 |
| Maintain | 1,955 |
| Gain 0.5 lb a week | 2,205 |
| Gain 1 lb a week | 2,455 |
Notice that 2 lb a week isn’t realistic for her: it would take her below 1,200 calories. Smaller, lighter people have less room for a deficit, which is why the same “lose 2 lb a week” goal can be sensible for one person and unsafe for another.
Calories by age
Calorie needs fall steadily with age because resting burn drops by about 5 calories a day for every year. This table shows maintenance calories for two example adults: a woman who is 5 ft 4 in and 150 lb, and a man who is 5 ft 10 in and 190 lb.
| Age | Woman, sedentary | Woman, moderate | Man, sedentary | Man, moderate |
|---|---|---|---|---|
| 25 | 1,692 | 2,186 | 2,224 | 2,872 |
| 35 | 1,632 | 2,109 | 2,164 | 2,795 |
| 45 | 1,572 | 2,031 | 2,104 | 2,717 |
| 55 | 1,512 | 1,954 | 2,044 | 2,640 |
| 65 | 1,452 | 1,876 | 1,984 | 2,562 |
These are maintenance calories. Subtract 500 for a 1-lb-a-week loss: the moderately active 45-year-old woman would aim for about 1,531, while a sedentary woman of the same size and age would land at 1,072, under the minimum. For her, more daily movement is the better lever than eating less.
Minimum calorie levels
Very low intakes make it hard to get enough protein, vitamins and minerals, and they’re harder to stick with. Harvard Health Publishing advises that intake shouldn’t fall below 1,200 calories a day for women or 1,500 for men unless a health professional is supervising. The calculator flags targets below these levels and suggests the fastest goal that stays above them.
Tips for using your number
- Treat it as a starting point. Eat at your target for two to three weeks, weigh yourself several times a week at the same time of day, and look at the trend rather than single readings.
- Adjust in small steps. If your weight isn’t moving as expected, change your intake by 100 to 200 calories a day and reassess.
- Recalculate as you go. Every 10 to 15 pounds lost lowers your maintenance needs, so a target that worked at the start will slow down later.
- Keep protein up while cutting. It helps preserve muscle. See the macro calculator for gram targets.
- Focus on food quality too. The Dietary Guidelines for Americans, 2025–2030, put calories under “eat the right amount for you” and stress whole foods and watching portion sizes of higher-calorie foods and drinks.
- Don’t out-eat your exercise logs. Fitness trackers often overestimate calories burned; the activity level already accounts for your usual exercise.
To see how your calorie burn splits between resting metabolism and activity, try the TDEE calculator, or compare BMR formulas side by side with the BMR calculator.
Assumptions and limitations
- Mifflin-St Jeor was developed from healthy adults. It’s less reliable for very muscular people, people with obesity, older adults and anyone with a medical condition that affects metabolism.
- The activity multipliers are broad categories, and they cause more error than the BMR equation itself.
- The 3,500-calories-per-pound rule ignores the fact that your body burns less as it gets smaller. Real weight loss usually slows over time; the NIH Body Weight Planner models this in more detail.
- This calculator is for adults who aren’t pregnant or breastfeeding, since both raise calorie needs.
Sources
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775–789.
- Harvard Health Publishing. Calorie counting made easy. Updated 2024.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–837.
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner.
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2025–2030.
This calculator gives general estimates for healthy adults and isn’t medical advice. If you have a health condition, are pregnant, or plan a large weight change, talk to your doctor or a registered dietitian.
Frequently asked questions
How many calories should I eat to lose weight?
Start from your maintenance calories, the amount that keeps your weight steady, and subtract about 500 a day to lose roughly 1 pound a week. A 35-year-old woman who is 5 ft 5 in, 160 lb and lightly active maintains at about 1,955 calories, so her target is about 1,455. Check your progress after two or three weeks and adjust.
What is the minimum number of calories I should eat?
Harvard Health Publishing advises that calorie intake shouldn't fall below 1,200 a day for women or 1,500 a day for men, except under the supervision of a health professional. Below that it gets hard to meet your nutrient needs from food. The calculator flags any target under these levels.
Is 500 calories a day really one pound a week?
Only roughly. The 3,500-calories-per-pound figure is an approximation, and as you lose weight your body burns less, so the same deficit produces slower loss over time. Expect faster loss in the first week or two (mostly water) and slower progress later.
Why does the calculator ask for my sex and age?
The Mifflin-St Jeor equation estimates resting calorie burn from weight, height, age and sex. Men typically burn more at the same size because they carry more lean mass, and resting burn falls with age. The equation subtracts 5 calories a day for each year of age.
Which activity level should I choose?
Pick the one that matches a typical week, not your best week. Most people with desk jobs who exercise a few times a week fit "light" or "moderate." If you're unsure, choose the lower level; it's easier to add calories later than to undo an overestimate.
How accurate is this calorie calculator?
It gives a good starting estimate, not a measurement. In a 2005 systematic review, the Mifflin-St Jeor equation predicted resting metabolic rate within 10% of measured values more often than other equations, but the activity multiplier adds more uncertainty. Your scale over a few weeks is the best test.
Updated November 2026. Results are estimates for educational purposes and depend on the inputs you provide.