Calorie calculator
Your resting metabolism, your total burn and the target that matches your goal — with every step of the arithmetic shown below, not hidden.
How this is calculated
Resting metabolism comes from the Mifflin–St Jeor equation, published in 1990 and still the default in clinical practice because it beat the older Harris–Benedict on modern populations:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s
s = +5 for men, −161 for women That is multiplied by an activity factor — 1.2 sedentary, 1.55 moderate, 1.9 very active — to get total daily energy expenditure. Your goal then moves the target away from that number.
When you give a target weight and a timeline, the deficit is derived rather than assumed: the difference in kilograms is multiplied by 7700 kcal — the energy in a kilogram of body fat — and spread across the days you asked for. Without a timeline it falls back to a flat 500 kcal.
The two guards
The result never drops below your BMR, no matter how short a timeline you choose, and a derived deficit is capped at 1000 kcal a day. Above roughly 1 % of body weight per week the plan is flagged as aggressive — the upper edge of what ACSM and ISSN guidance considers reasonable for keeping muscle and, more importantly, for still doing it in month three.
These are the same numbers and the same guards the Talk2Fit app applies when it builds your plan — the calculator is the app's own arithmetic, not a separate approximation.
Questions
Which formula does this use?
Mifflin–St Jeor for resting metabolism, then an activity multiplier of 1.2, 1.55 or 1.9 for total daily energy. It is the equation dietitians reach for first, and the same one running inside the Talk2Fit app.
Why is my deficit capped?
Two guards. Your target never drops below your resting metabolism, however aggressive a timeline you pick — eating under it is where people lose muscle and adherence. And a derived deficit is capped at 1000 kcal a day, so an impossible request (30 kg in a month) cannot turn into an absurd number.
How accurate is it?
It is an estimate, and honest estimates carry error bars: predictive equations land within roughly ±10 % for most people, and further out at the extremes of body composition. Treat the number as a starting point, then adjust by what the scale actually does over two or three weeks.
What counts as moderate activity?
Three to five sessions a week, or a job that keeps you on your feet. Desk work with occasional walking is sedentary — most people overestimate this one, and the multiplier is where an inflated guess does the most damage.
Do I have to weigh my food to use this?
No. The target is the number worth knowing; hitting it is a separate problem. That is the part the app takes over — you say or photograph what you ate and it does the arithmetic.