How to Use This Calculator
- 1
Select your sex and age
The equation adjusts for both: men get a +5 constant, women a −161, and estimated needs decline by about 50 calories per decade of age.
- 2
Enter your height and weight
Choose US units or Metric first, then fill in the fields. These two numbers drive most of the result, so use current, honest values rather than aspirational ones.
- 3
Choose an activity level
Count only exercise that actually happens most weeks. A desk job with no workout routine is sedentary; save the top tiers for people who train hard nearly every day or do physical labor.
- 4
Read your maintenance number
The headline figure is the estimated daily intake that keeps your weight where it is — your total daily energy expenditure, or TDEE.
- 5
Pick a goal target
The smaller cards subtract or add 250 and 500 calories from maintenance, corresponding to roughly half a pound and one pound of weight change per week.
How It Works
This calculator runs on the Mifflin-St Jeor equation, published in 1990 and endorsed by the Academy of Nutrition and Dietetics as the most reliable resting-metabolism formula for the general population:
BMR is what your body burns at complete rest. To estimate your total daily burn, the BMR is multiplied by an activity factor: 1.2 for sedentary, 1.375 for light, 1.55 for moderate, 1.725 for active, and 1.9 for very active. The goal targets then shift that maintenance figure by 250 or 500 calories per day, since a daily 500-calorie deficit works out to roughly one pound of loss per week.
Worked example
A 30-year-old man who stands 5 ft 10 in (177.8 cm) and weighs 180 lb (81.6 kg):
BMR = 10 × 81.6 + 6.25 × 177.8 − 5 × 30 + 5 ≈ 1,783 calories.
With moderate activity, that becomes 1,783 × 1.55 ≈ 2,763 calories per day to maintain his weight — and about 2,263 calories to lose roughly one pound per week.
Frequently Asked Questions
How many calories should I eat a day?
US dietary guidelines put typical needs around 2,000–2,400 calories for adult women and 2,400–3,000 for adult men, but those are broad averages. Your personal number depends on size, age, and movement: a small sedentary woman might maintain on 1,800 calories while a tall active man needs well over 3,000. The calculator above gives a figure tailored to your own stats.
What is the difference between BMR and TDEE?
BMR — basal metabolic rate — is the energy your body spends just staying alive: breathing, circulation, cell repair. It typically accounts for 60–70% of everything you burn. TDEE, total daily energy expenditure, multiplies BMR by an activity factor to fold in movement and exercise. The maintenance number this calculator shows is your estimated TDEE; eating that amount should hold your weight steady.
Is a 500-calorie daily deficit safe?
For most adults, yes — it produces roughly one pound of loss per week under the classic 3,500-calories-per-pound rule, a pace most guidelines consider sustainable. Just don't cut too deep: intakes below about 1,200 calories for women or 1,500 for men make it hard to get enough protein and micronutrients, and should only be attempted under medical supervision.
Why use Mifflin-St Jeor instead of Harris-Benedict?
The Harris-Benedict equation dates to 1919, and bodies and lifestyles have changed considerably since. Mifflin-St Jeor, published in 1990, predicted measured resting metabolic rate within 10% for more subjects in validation studies, which is why the Academy of Nutrition and Dietetics names it the preferred formula for healthy adults. Harris-Benedict tends to overestimate needs by roughly 5%.
Should I eat back the calories I burn exercising?
Usually not — your activity multiplier already bakes regular workouts into the maintenance number, so adding them again double-counts the effort. The exception is unusual exertion outside your normal routine, like a long hike or a race. Even then, fitness trackers commonly overstate burn by 20–40%, so eating back about half of what the watch claims is the safer play.
Why has my weight loss stalled on the same calories?
Two forces are at work. A lighter body simply costs less to run — every 10 pounds lost trims roughly 50–100 calories from your daily burn — and metabolic adaptation slows things a little further as your body defends its energy stores. Recalculate your targets after every 10–15 pounds lost, and remember water retention can mask fat loss on the scale for weeks.