The question "how many calories should I eat per day?" has no single answer — it depends on your biology, body size, age, sex, and how active you are. Eating the wrong amount (too little or too much) produces predictable, measurable consequences. Here is how to find your number.
Your Daily Calorie Need Is Called TDEE
Your Total Daily Energy Expenditure (TDEE) is the number of calories your body burns every day — at rest, through digestion, and through movement. Eating at your TDEE maintains your current weight. Eating below it causes weight loss; eating above it causes gain.
TDEE is calculated in two steps:
Step 1: Calculate BMR (Basal Metabolic Rate)
BMR is the calories your body burns just to stay alive — breathing, circulation, organ function. The most clinically validated formula is the Mifflin-St Jeor equation:
For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Example — 35-year-old woman, 65 kg, 165 cm: BMR = (10 × 65) + (6.25 × 165) − (5 × 35) − 161 = 650 + 1031.25 − 175 − 161 = 1,345 calories
Step 2: Multiply BMR by Activity Multiplier
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days/week | 1.375 |
| Moderately active | Exercise 3–5 days/week | 1.55 |
| Very active | Hard exercise 6–7 days/week | 1.725 |
| Extra active | Physical job + intense exercise | 1.9 |
Example continued: 1,345 × 1.375 (lightly active) = 1,849 calories/day TDEE
Calorie Targets by Goal
| Goal | Daily Calorie Target | Expected Outcome |
|---|---|---|
| Aggressive weight loss | TDEE − 500 to − 750 kcal | ~0.5–0.75 kg per week |
| Moderate weight loss | TDEE − 300 to − 500 kcal | ~0.3–0.5 kg per week |
| Maintenance | TDEE | Weight stable |
| Lean muscle gain | TDEE + 200 to + 300 kcal | Slow muscle gain |
| Aggressive bulk | TDEE + 400 to + 600 kcal | Fast muscle + some fat |
Important: Never go below 1,200 calories/day for women or 1,500 calories/day for men without medical supervision — below these thresholds, you risk nutrient deficiencies and metabolic adaptation.
Reference Calorie Table by Demographics
The table below shows estimated TDEE at moderate activity using Mifflin-St Jeor:
| Age | Male, 75 kg, 175 cm | Female, 60 kg, 163 cm |
|---|---|---|
| 20 | 2,790 kcal | 2,130 kcal |
| 30 | 2,740 kcal | 2,080 kcal |
| 40 | 2,690 kcal | 2,030 kcal |
| 50 | 2,640 kcal | 1,980 kcal |
| 60 | 2,590 kcal | 1,930 kcal |
TDEE declines with age because BMR naturally decreases — approximately 1–2% per decade after age 30.
Why Calorie Deficits Slow Down Over Time
When you lose weight, your BMR drops — because you are carrying less body mass that needs to be maintained. A person who loses 10 kg will burn roughly 100–150 fewer calories per day at rest. This is why weight loss often plateaus and why TDEE should be recalculated every 4–6 weeks.
Calculate Your Exact Calorie Need
Use our Calorie Calculator to calculate your personalised daily calorie target based on the Mifflin-St Jeor equation and your activity level. You can also use the TDEE Calculator to see a complete breakdown of your energy expenditure by activity category.
This article is for educational purposes and does not replace personalised dietary advice from a registered dietitian.
Frequently Asked Questions
Q: How do I calculate how many calories I should eat per day? A: First calculate BMR using the Mifflin-St Jeor equation, then multiply it by an activity multiplier (1.2 for sedentary up to 1.9 for extra active) to get your TDEE, then adjust up or down from TDEE based on your goal.
Q: What is the lowest number of calories I should eat safely? A: Without medical supervision, women should not go below 1,200 calories/day and men should not go below 1,500 calories/day, since lower intakes risk nutrient deficiencies and metabolic adaptation.
Q: Why does my calorie need decrease as I get older or lose weight? A: BMR naturally declines about 1–2% per decade after age 30, and losing roughly 10 kg of body mass reduces resting calorie burn by about 100–150 calories per day, which is why TDEE should be recalculated every 4–6 weeks.
