How Many Calories Should I Eat a Day? A Worked Answer
If you search “how many calories should I eat a day?” you will find answers from 1,200 to 3,000 — and none of them is your answer, because none of them knows your weight, height, age or how you spend your days. There is no magic number. There is a calculation, and once you see it worked, you can use it for yourself and then check it against reality.
Start with the only two numbers that matter
BMR — basal metabolic rate — is the energy you would burn lying still all day, keeping your body running. TDEE — total daily energy expenditure — is BMR multiplied by how active you actually are. Your maintenance calories are your TDEE: eat at it and your weight holds steady.
The formula we use is Mifflin–St Jeor, the equation a 2005 review in the Journal of the American Dietetic Association found most accurate among the common formulas:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
A worked example
Take a man, 32 years old, 80 kg, 178 cm, moderately active (3–5 training days a week). His BMR is 1,768 kcal a day. Multiply by the activity factor for moderately active, 1.55:
TDEE = 1,768 × 1.55 = 2,740 kcal
From that one maintenance number, the goals fall out:
| Goal | Daily calories | Expected trend |
|---|---|---|
| Lose faster (−750) | 1,990 kcal | ≈ −0.68 kg/week |
| Lose (−500) | 2,240 kcal | ≈ −0.45 kg/week |
| Maintain | 2,740 kcal | steady |
| Gain (+300) | 3,040 kcal | slow gain, mostly muscle with training |
The same man sedentary (×1.2) maintains at just 2,121 kcal — a 600-kcal swing from activity alone, which is why copying someone else’s “perfect” calorie target so often fails.
Why blanket numbers mislead
The label figure of 2,000 kcal (and its cousin, 2,500 for men) describes a statistical middle that almost nobody actually occupies. A smaller, sedentary woman may maintain near 1,650 kcal; a tall, active man may need 3,200. Eating the label number in either case means slowly gaining or losing without ever understanding why. Two minutes with a TDEE calculator built on your own stats beats a national average every time.
The safety floors nobody should cross quietly
There is a reason our calculator never sets a target below 1,200 kcal a day: below that level it becomes very hard to cover basic nutrition, and unsupervised very-low-calorie dieting carries real risks. If your “lose faster” maths lands you on that floor, the correct response is not to eat less — it is to pick the gentler deficit and, if you want faster change, move more instead. And some people should not be setting deficit targets from a website at all: if you are under 18, pregnant, breastfeeding, or managing a medical condition, skip the calculator and talk to a professional. Our disclaimer is blunt about this because it matters.
The two-week check: how to make the number yours
Here is the part most calorie guides skip. The equation gives you an estimate — a good one, but individual bodies routinely differ from it by 10% or more. The fix is a simple loop:
- Eat at your target for two to three weeks. Weigh yourself a few times a week, same time of day, and average each week.
- Compare the trend with the goal. Losing at roughly the expected rate? The number is right — keep going. Losing much faster or slower?
- Adjust by 100–200 kcal in the appropriate direction and repeat. Losing too slowly on a deficit usually means the activity multiplier overshot — stepping it down one level is often a more honest correction than cutting food.
After one or two rounds of this loop, you no longer have a calculator’s number. You have your number, measured on your own body, and it is worth more than any formula.
What about macros?
Calories decide the direction of your weight; macros decide what the change is made of. Once your calorie target is set, protein is the first macro worth fixing — especially in a deficit, where enough protein is the difference between losing fat and losing muscle along with it. Our protein guide gives the gram-per-kilo ranges by goal, and the calorie deficit guide explains how deficit size trades speed against sustainability.
Frequently asked questions
How many calories should I eat to lose weight? For most adults, maintenance minus 300–500 kcal is the sustainable starting point — roughly 0.3–0.45 kg a week. Bigger deficits are faster on paper and harder to live with.
How many calories should I eat to maintain my weight? Your TDEE, exactly as calculated above — then verified with the two-week check, because your true maintenance is whatever keeps your weight trend flat.
Do I need to hit the number exactly every day? No. Bodies respond to averages. A day 200 kcal over followed by a day 200 kcal under is, for weight purposes, the same as two perfect days. Weekly averages are a calmer and equally effective way to track.
Are online calorie calculators accurate? They are accurate estimates — the Mifflin–St Jeor equation is the best-validated of the common formulas — but no equation replaces the two-week check on your own scale.
All figures on this page are general educational estimates. See the methodology for every formula and source we use.