You can get a good calorie target by starting from your body’s estimated needs, then nudging up or down depending on whether you want to lose, maintain, or gain weight.

1. Quick rule-of-thumb ranges

If you just want a fast ballpark and don’t have your height/weight handy, many adults fall roughly in these ranges for maintenance (not losing or gaining):

  • Women: about 1,800–2,200 calories per day, depending on size and activity.
  • Men: about 2,200–2,800 calories per day, depending on size and activity.
  • To lose weight safely, people often eat about 300–500 calories below their maintenance number.
  • To gain weight or muscle, people often eat about 200–400 calories above maintenance.

These are averages, not personal prescriptions, but they give a starting point you can refine.

2. How to estimate your number (simple method)

If you want something more tailored without doing a lot of math, you can use this lightweight approach:

  1. Pick a body‑weight factor based on your activity:
    • Mostly sitting (little exercise): 28–30 calories per kg of body weight.
    • Lightly active (1–3 workouts/week or lots of walking): 30–33 calories/kg.
    • Moderately active (3–5 workouts/week): 33–36 calories/kg.
    • Very active (hard training or physical job): 36–40 calories/kg.
  2. Multiply your weight in kg by that factor.
    • Example: 70 kg, lightly active → about 70 × 31 ≈ 2,170 calories/day for maintenance.
  3. Adjust for your goal:
    • Weight loss: subtract 300–500 calories from that maintenance estimate.
    • Weight gain: add 200–400 calories.

This “weight × factor” method is a simplified version of what more formal calculators do using basal metabolic rate (BMR) and activity multipliers.

3. The more precise way (BMR + activity)

If you like numbers, most professional calculators use the Mifflin‑St Jeor equation to estimate BMR (the energy your body needs at rest). Then they multiply it by an activity factor:

  • Men: BMR=10×weight (kg)+6.25×height (cm)−5×age (y)+5\text{BMR}=10\times \text{weight (kg)}+6.25\times \text{height (cm)}-5\times \text{age (y)}+5BMR=10×weight (kg)+6.25×height (cm)−5×age (y)+5.
  • Women: BMR=10×weight (kg)+6.25×height (cm)−5×age (y)−161\text{BMR}=10\times \text{weight (kg)}+6.25\times \text{height (cm)}-5\times \text{age (y)}-161BMR=10×weight (kg)+6.25×height (cm)−5×age (y)−161.

Then multiply BMR by your activity level:

  • Sedentary (little exercise): BMR × 1.2
  • Lightly active (1–3 days/week): BMR × 1.375
  • Moderately active (3–5 days/week): BMR × 1.55
  • Very active (6–7 days/week): BMR × 1.725
  • Extra active (physical job or 2× training): BMR × 1.9

That gives you your approximate maintenance calories (also called TDEE). From there, you adjust up or down depending on your goal, just like in the simple method.

Example: A 35‑year‑old man, 180 cm, 80 kg, moderately active, aiming to lose about 0.5 kg/week typically lands near 2,100 calories/day.

4. How to use your number in real life

Once you have a starting target:

  • Track what you eat (even roughly) for 2–3 weeks.
  • Watch weight and how your clothes feel, not just the scale day‑to‑day.
  • If weight isn’t moving as expected after 2–3 weeks:
    • For weight loss: reduce by another 100–150 calories or slightly increase activity.
    • For weight gain: add 100–150 calories.
  • Recalculate or tweak after any 4–6 week period or ~5 kg change in weight, because needs change as your body changes.

5. Safety notes

  • Aim for gradual weight loss, usually around 0.25–0.75 kg (0.5–1.5 lb) per week for most people.
  • Very low‑calorie diets can be risky and are usually only done under medical supervision.
  • If you have a medical condition (like diabetes, thyroid issues, history of eating disorders, or are pregnant/breastfeeding), talk to a healthcare professional or registered dietitian before making big calorie changes.

If you tell me your age, sex, height, weight, and how active you are, I can walk you through a more personalized calorie estimate step by step.