There is no single number for how many calories you should eat per day. A 25-year-old construction worker and a 60-year-old office worker can differ by more than 1,000 calories a day, and both numbers can be right. The honest answer comes from three steps: your resting burn, your activity level, and your goal. This guide walks through all three with worked numbers you can check, and shows where the usual shortcuts go wrong. Every worked number below was recomputed for this article.
The answer in 30 seconds
- Your maintenance calories are called TDEE (total daily energy expenditure): the calories you burn in a typical day, movement included. Eat at TDEE and your weight stays roughly stable.
- To lose weight, start at TDEE minus 500 calories a day, which predicts roughly 0.5 kg (about 1 lb) a week. To gain slowly, start at TDEE plus 300.
- The most widely used resting-burn formula is Mifflin-St Jeor (1990), derived from 498 healthy adults. It needs only weight, height, age, and sex.
- Commonly cited safety floors are about 1,200 calories a day for women and 1,500 for men. Going below them without medical supervision risks nutrient gaps and muscle loss.
- Recalculate every time your weight changes by 10 to 15 lb, because a lighter body burns less.
- Use the free calorie calculator to personalize it: enter your age, sex, height, weight, activity level, and goal, and it gives your daily target plus BMR, TDEE, and a macro split.
Step 1: your resting burn (BMR)
BMR (basal metabolic rate) is the energy your body burns at complete rest: breathing, circulation, organ function, body temperature. It is the floor of your energy use, typically around 60 to 75% of everything you burn in a day, and it is not a target to eat at — nobody lies still all day.
The Mifflin-St Jeor equation, published in 1990 and derived from resting measurements on 498 healthy adults aged 19 to 78, is the formula clinical references treat as the most accurate of the common ones for healthy adults:
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161The original paper reported slightly more precise coefficients (9.99 for weight, 4.92 for age), but the authors showed rounding them to 10 and 5 did not change the predictions, which is why every calculator uses the rounded form. The equation explains about 71% of the variation between people, so treat its output as a solid estimate, not a measurement: muscle mass, genetics, and health conditions move real burn away from the formula in both directions.
Step 2: your maintenance calories (TDEE)
Multiply BMR by an activity factor to get TDEE. This is the step where most people go wrong, and almost always in the same direction: overestimating activity. A desk job with three gym sessions a week is moderately active, not very active. A physical job or twice-daily training is very active. Be honest here, because every later number inherits this choice.
| Activity level | Factor | What it means |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise, desk job |
| Lightly active | 1.375 | Light exercise 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Extremely active | 1.9 | Very hard exercise or a physical job |
TDEE is your maintenance line. Eat at it and weight holds steady; the goal adjustments in the next section all hang off it.
Worked example 1: a 30-year-old man, 80 kg, 180 cm, moderately active
BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 calories a day at rest.
| Activity level | TDEE (BMR × factor) |
|---|---|
| Sedentary (1.2) | 2,136 |
| Lightly active (1.375) | 2,448 |
| Moderately active (1.55) | 2,759 |
| Very active (1.725) | 3,071 |
| Extremely active (1.9) | 3,382 |
At moderately active, his maintenance is 2,759 calories. His targets: lose weight at 2,759 − 500 = 2,259 calories; gain slowly at 2,759 + 300 = 3,059 calories. Notice how much the activity choice matters: the same man is 2,136 sedentary and 3,382 extremely active — a 1,246-calorie swing from one honest reassessment.
Worked example 2: a 40-year-old woman, 65 kg, 165 cm, lightly active
BMR = 10 × 65 + 6.25 × 165 − 5 × 40 − 161 = 650 + 1,031.25 − 200 − 161 = 1,320 calories a day at rest (1,320.25 before rounding).
TDEE = 1,320.25 × 1.375 = 1,815 calories to maintain. Her targets: lose weight at 1,815 − 500 = 1,315 calories, which sits above the commonly cited 1,200 floor for women, so the full 500 deficit is usable here; gain slowly at 1,815 + 300 = 2,115 calories. If her TDEE had been lower — a smaller or older woman, or a sedentary one — the 500 deficit could push below the floor, and the right move would be a smaller deficit, not a crash diet.
Step 3: set your goal target
- Maintain: eat at TDEE. This is also the right starting point if you are new to tracking: two weeks at maintenance teaches you what your current intake actually is before you change it.
- Lose weight: start at TDEE minus 500, predicting roughly 0.5 kg (about 1 lb) a week. The math behind it is the old rule that a pound of body fat stores about 3,500 calories, so 500 a day times 7 days is 3,500 a week. Treat that as a rule of thumb, not a promise: as Mayo Clinic explains in its calorie-counting guide, cutting 500 a day typically yields about half a pound to a pound a week, but it varies with body, goal size, sex, and activity — and weight lost is a mix of fat, lean tissue, and water, not pure fat.
- Gain weight: start at TDEE plus 300 for a slow, lean gain. The Trencada calculator uses plus 300 for its gain option; general guidance often quotes plus 250 to 500. Smaller surpluses add less fat alongside the muscle.
Whichever goal you pick, the number is a starting point, not a verdict. Track weight for two to three weeks: if the trend matches the goal, hold the number; if it does not move, adjust by 100 to 200 calories and watch again. Bodies adapt as weight changes, which is why the recalculation rule matters.
Safety floors, and who should not use a calculator
The commonly cited floors — about 1,200 calories a day for women, about 1,500 for men — are not magic lines, but going below them without supervision is where problems concentrate: nutrient deficiencies, muscle loss, gallstones, and hormonal disruption. If your TDEE minus 500 lands below your floor, use a smaller deficit and add activity instead of eating less.
These formulas were built for healthy adults. They do not apply to children, pregnant or breastfeeding women, competitive athletes, or people with conditions that affect metabolism — thyroid disorders, diabetes, eating disorders, and others. The Trencada calculator carries the same warning on its results: its numbers are estimates for general guidance only, not medical advice, and calorie needs vary with muscle mass and health conditions. If any of those apply to you, or if you are considering a large deficit, talk to a qualified professional before starting.
Why your number moves over time
Three things change TDEE enough to matter. First, weight itself: a lighter body costs less to run, so every 10 to 15 lb lost lowers maintenance, and a deficit that worked at the start quietly becomes maintenance. Second, activity: a new training habit or a switch to a desk job moves the factor, sometimes by hundreds of calories. Third, body composition: muscle burns more at rest than fat does, so two people at the same weight can have different BMRs — one reason the formula, which cannot see muscle mass, is an estimate.
The practical rule covers all three: recheck your numbers whenever your weight moves 10 to 15 lb, whenever your activity pattern changes for more than a few weeks, and whenever progress stalls for a month despite honest tracking. A stall usually means the number is stale, not that the method failed.
Using the Trencada calorie calculator
The calorie calculator runs the same method as this guide, entirely in your browser — nothing is uploaded. Choose Metric or Imperial units, then enter your age, sex, height, and weight. Pick the activity level that best matches your week, from sedentary to extremely active, and select your goal: lose weight (TDEE minus 500, about 0.5 kg a week), maintain (stay at TDEE), or gain weight (TDEE plus 300, slow lean gain). Press Calculate calories to see your daily target plus your BMR, your TDEE, and a protein, fat, and carbohydrate gram split.
If you track weight and health goals together, the BMI calculator uses the same weight input, and the body fat guide explains what body composition adds to the picture: how to calculate body fat percentage.
Frequently asked questions
How many calories should I eat to lose weight?
Start at your TDEE minus 500 a day, which predicts roughly 0.5 kg (about 1 lb) a week, and stay above the commonly cited floors of 1,200 calories for women and 1,500 for men. If that deficit takes you below your floor, use a smaller deficit and add activity instead.
What is the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE is BMR multiplied by an activity factor: everything you burn in a typical day, movement included. BMR is the floor; TDEE is the maintenance line you actually eat against.
Is 1,200 calories enough?
For most women it is a floor, not a target — the lowest intake generally attempted without medical supervision. Smaller, older, or sedentary women can have a TDEE near it, which means their deficit must be smaller than 500, not that they should eat below it.
How accurate is the Mifflin-St Jeor equation?
It is the most validated of the common formulas for healthy adults, derived from 498 people, but it still explains only about 71% of the variation between individuals. Expect it to be close, then adjust from two to three weeks of real weight trends — that feedback loop is more accurate than any formula.
Do I need to count calories forever?
No. Most people use tracking to learn portion sizes and their own patterns, then keep the habits with looser tracking. Recheck with the calorie calculator whenever your weight moves 10 to 15 lb or your activity changes.
Can children, pregnant women, or athletes use this method?
No. The formula was built for healthy adults aged roughly 19 to 78. Children, pregnancy, breastfeeding, and elite training all need different equations and professional guidance.
