How to calculate your daily calorie needs

Your calorie needs are how much energy your body burns in a day. You cannot measure that exactly without a lab, but an equation gets within about 10% — close enough to start, and your actual weight trend fine-tunes it from there.

Step 1. Basal metabolic rate (BMR)

BMR is the energy your body uses at rest — breathing, heartbeat, brain, body temperature. The most widely used equation for adults is Mifflin-St Jeor (1990):

• Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

In pounds and inches, the same equation is 4.536 × weight (lb) + 15.88 × height (in) − 5 × age, then +5 for men or −161 for women.

If you know your body fat percentage, the Katch-McArdle equation can be more accurate: 370 + 21.6 × lean body mass (kg). It accounts for muscle burning more energy than fat.

Step 2. Add activity (TDEE)

Total daily energy expenditure (TDEE) is BMR plus all your movement. The classic method multiplies BMR by an activity factor:

• 1.2 — desk job, little or no exercise;
• 1.375 — light exercise 1–3 days a week;
• 1.55 — moderate exercise 3–5 days a week;
• 1.725 — hard exercise 6–7 days a week;
• 1.9 — physical job or training twice a day.

The most common mistake is overestimating activity. Three gym sessions a week on top of a desk job is closer to 1.375–1.55 than 1.725.

Step 3. Adjust for your goal

• Maintain — eat around your TDEE.
• Lose weight — a deficit of 10–20% of TDEE usually means losing about 0.5–1% of body weight a week without constant hunger. The old rule of thumb — 1 lb of fat ≈ 3,500 kcal, so 500 kcal a day ≈ 1 lb a week — is rough: real loss is uneven because of water.
• Gain weight — a surplus of 5–10%, to gain mostly muscle rather than fat.

Cutting much harder backfires: hunger rises, energy drops and you lose muscle. More in how to lose weight without starving.

Worked examples

Man, 30, 5′11″ (71 in), 176 lb, light exercise: BMR = 4.536 × 176 + 15.88 × 71 − 150 + 5 ≈ 1,780 kcal. TDEE ≈ 1,780 × 1.375 ≈ 2,450 kcal. For fat loss with a 15–20% deficit — about 1,950–2,080 kcal.

Woman, 35, 5′5″ (65 in), 154 lb, desk job: BMR = 4.536 × 154 + 15.88 × 65 − 175 − 161 ≈ 1,395 kcal. TDEE ≈ 1,395 × 1.2 ≈ 1,675 kcal. For fat loss — about 1,400–1,500 kcal.

How Temfy Nutri calculates it

Temfy Nutri works out your targets on first launch from a short setup: goal, sex, age, height (cm or inches), weight (kg or lb), body fat (you can pick “I don't know” or compare yourself with reference pictures), goal weight, how much you walk per day and how often you train. It goes a bit further than “BMR × multiplier”:

• If you skip body fat, it is estimated from BMI and age (the Deurenberg formula).
• BMR uses Katch-McArdle, cross-checked against Mifflin-St Jeor; if they differ by more than 15%, the app takes the average.
• Workouts and walking are added separately, based on your body weight, instead of one blanket multiplier.
• The weight-loss deficit is capped at 20% of TDEE and 0.75% of body weight a week, and calories never go below your BMR or below 1,500 kcal for men and 1,200 kcal for women.

For the same man (30, 180 cm / 5′11″, 80 kg / 176 lb, light exercise, walking about 2 miles a day, goal: lose weight) the app gives about 1,820 kcal: 140 g protein, 51 g fat and 200 g carbs. How calories split into macros is covered in how to count macros.

Your number is a starting point

Any equation can be 5–15% off either way. After 2–3 weeks, check against reality: if your weight has not moved despite honest logging, drop 100–200 kcal; if you are losing faster than 1% a week, add some back. Go by the weekly average, not daily swings.