The calories you need a day are your basal metabolic rate times an activity factor, from 1.2 if you are sedentary to 1.9 if very active. US dietary guidelines estimate 1,600 to 2,400 calories a day for adult women and 2,000 to 3,000 for adult men; to lose about a pound a week, eat about 500 calories a day less than you burn. A moderately active 40-year-old man of 5 ft 10 in and 180 lb needs about 2,690 calories a day to stay at his weight.
Enter your details for your own maintenance calories and the targets for losing or gaining weight at a steady pace.
Worked example
Sex: MaleAge: 40 yearsHeight: 5 ft 10 inWeight: 180 lbActivity: Moderately active — moderate exercise 3–5 days a week
Calories to maintain your weight: 2,690 kcal/day Moderately active
A moderately active 40-year-old man of 5 ft 10 in and 180 lb needs about 2,690 calories a day to keep his weight. To lose about a pound a week, he would aim for around 2,190.
Open this example in the calculator →How to use the Calorie Calculator
- Choose your sex and enter your age.
- Choose US or metric units and enter your height and weight.
- Pick the activity level that matches a typical week — if unsure, the lower one.
- Read your maintenance calories and the target for your goal.
How the calculator works
First it estimates your basal metabolic rate with the Mifflin–St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. Then it multiplies by an activity factor to get your total daily energy expenditure (TDEE) — the calories that keep your weight steady. Goals add or subtract from that: about 500 calories a day for each pound a week.
Worked through for the example above: 10 × 81.6 + 6.25 × 177.8 − 5 × 40 + 5 = 1,733 calories at rest; × 1.55 for moderate activity = 2,690 calories a day.
Estimated calorie needs by age (US Dietary Guidelines)
| Age | Women | Men |
|---|---|---|
| 19–30 | 1,800–2,400 | 2,400–3,000 |
| 31–50 | 1,800–2,200 | 2,200–3,000 |
| 51–60 | 1,600–2,200 | 2,200–2,800 |
| 61 and over | 1,600–2,000 | 2,000–2,600 |
The low end is for sedentary people and the high end for active ones, at a reference size. The guidelines' reference woman is 5 ft 4 in and 126 lb; the reference man, 5 ft 10 in and 154 lb — so people larger than that need more.
How many calories to lose weight?
- 250 a day less than maintenance: about 0.5 lb (0.25 kg) a week — slow but easy to sustain.
- 500 a day less: about 1 lb (0.45 kg) a week — the usual recommendation.
- 1,000 a day less: about 2 lb (0.9 kg) a week — the upper limit most guidelines suggest, and only if it leaves you above the minimum.
The 3,500-calories-per-pound rule overstates loss over months, because a lighter body burns less. Recalculate every 10 lb or so, or use the goal weight calculator to plan the timeline.
Calories to gain weight
For someone underweight or building muscle, 250 to 500 calories a day above maintenance gains roughly 0.5 to 1 lb a week. Pair it with strength training and enough protein so that more of the gain is muscle.
Calories are not the whole story
The same number of calories can come from very different diets. Protein and fiber keep you fuller per calorie, and whole foods are harder to overeat than ultra-processed ones. Sleep, stress and medicines also affect appetite and weight. A registered dietitian can tailor a plan if you have a medical condition.
Frequently asked questions
How many calories should I eat a day?
Enough to match what you burn if you want to keep your weight. For adults that is usually 1,600 to 2,400 for women and 2,000 to 3,000 for men, depending on size, age and activity. Enter your details above for your own figure.
How many calories should I eat to lose weight?
About 500 calories a day less than your maintenance figure to lose roughly a pound a week. Most guidance advises not going below about 1,200 a day for women or 1,500 for men without medical supervision.
How accurate are calorie calculators?
For most people the estimate is within about 10% of what they actually burn. Use it as a starting point, then adjust by watching your weight over two to three weeks.
What activity level should I choose?
Pick the one that fits a typical week, not your best week. Sedentary means a desk job with little exercise; moderately active means exercise 3 to 5 days a week. If in doubt, choose the lower level.
Do I need fewer calories as I get older?
Yes, usually. Calorie needs fall with age, mostly because muscle mass and activity tend to fall. Staying active and doing strength exercise slows that decline.
Does exercise let me eat more?
Yes — it is part of your activity level. But calories burned in exercise are often overestimated by fitness trackers and machines, so it is safer not to eat back all of them.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247 — American Journal of Clinical Nutrition
- Dietary Guidelines for Americans, 2020–2025 — U.S. Department of Agriculture and HHS
- Body Weight Planner — National Institute of Diabetes and Digestive and Kidney Diseases (NIH)
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837 — The Lancet
- Overweight and obesity management (NG246), 2025 — National Institute for Health and Care Excellence (UK)
For general information only — not a diagnosis or a substitute for advice from a doctor. How we calculate.