Calculate your daily calories
Mifflin-St Jeor × activity multiplier, goal shifted by 500 kcal and never below 1,200. These are the exact numbers Morsel suggests in onboarding. Estimates for self-tracking, not medical advice.
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Step 1: resting energy (Mifflin-St Jeor)
The Mifflin-St Jeor equation, published in 1990, is the estimate dietitians most commonly use for resting metabolic rate — the calories your body burns lying still for a day. In kcal per day: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years), plus 5 for men or minus 161 for women. A 34-year-old woman, 168 cm and 72 kg, has a resting burn of about 1,400 kcal.
Step 2: your activity multiplier
Resting burn is multiplied by a factor that accounts for movement and exercise. The honest caveat: people overestimate their activity, and a desk job with a gym visit three days a week is “lightly active”, not “very active”.
- Sedentary (desk work, little exercise): × 1.2
- Lightly active (exercise 1–3 days a week): × 1.375
- Moderately active (exercise 3–5 days a week): × 1.55
- Very active (exercise 6–7 days a week): × 1.725
- Extra active (hard training or a physical job): × 1.9
Step 3: shift for your goal
The result is your total daily energy expenditure, the amount that keeps your weight where it is. To lose weight, eat less than that; to gain, eat more. Half a kilo of body fat holds roughly 3,500 kcal, so a 500 kcal daily deficit works out to about half a kilo — one pound — a week, which is the pace most guidelines call sustainable. Morsel suggests exactly that: your daily burn minus 500 to lose, plus 500 to gain, rounded to the nearest ten.
Two guard rails. Morsel never suggests less than 1,200 kcal a day, because below that a tracking app has no business making recommendations. And every number here is an estimate from population averages; individual metabolism varies by a few hundred calories either way. Track for two or three weeks, watch the weight trend, and adjust the goal by 100 to 200 kcal rather than trusting the equation to the calorie.
This is not medical advice
The calculator is a starting point for self-tracking, not a prescription. If you are pregnant, under 18, managing a medical condition, or have any history of disordered eating, talk to a doctor or dietitian before setting a calorie target — and if tracking feels stressful or harmful, stop. Your wellbeing comes first.
Questions people ask
- How many calories should a woman eat a day?
- It depends on height, weight, age and activity, which is why the calculator asks. For a moderately active adult woman the daily burn typically lands around 1,900 to 2,300 kcal; to lose weight at a gentle pace, roughly 500 less.
- How many calories should a man eat a day?
- For a moderately active adult man the daily burn typically lands around 2,400 to 2,900 kcal, again depending on size and age. Subtract about 500 to lose roughly a pound a week.
- Is Mifflin-St Jeor better than Harris-Benedict?
- Mifflin-St Jeor is newer (1990) and, in comparison studies, tends to be the more accurate of the two for most adults, which is why it is the one dietitians and most tracking apps use. Both are estimates; the trend in your own weight over a few weeks is the real answer.