Behind the number
Step one: your basal metabolic rate
Your basal metabolic rate (BMR) is the energy your body uses at complete rest, before movement is added. This estimate uses the Henry (2005) equations specified by the Nordic Nutrition Recommendations. They use separate formulas for men and women and take weight, height, and age into account. Henry publishes the formulas in three age bands. This calculator blends between them instead of jumping at each boundary, so we say 'based on' rather than claiming to reproduce the equations exactly. It used to use the older Mifflin-St Jeor equation, which was fitted mostly to middle-aged adults and drifts low for very small or older bodies. Henry holds up better across the full adult range.
Step two: your activity multiplier
That BMR is then multiplied by an activity factor. We use the midpoints of the Nordic Nutrition Recommendations' PAL bands (NNR 2023). The values are 1.40 for seated work with little movement and little free-time activity, 1.65 for seated work with some movement and some free-time activity, 1.85 for work that mixes standing and moving or seated work plus daily activity, and 2.10 for physically hard work or daily hard training. Most people overestimate this step. If you have a desk job and train a few times a week, the lower two bands are usually closer to reality than the flattering option.
Step three: the goal adjustment
The headline number is your estimated maintenance, the intake at which your weight roughly holds. If you choose a goal, the calculator suggests a modest range about 200 to 400 kcal below or above maintenance. In the CaloriSpy app itself, a real loss plan's pace is a quarter, half, three-quarters, or all of your own safe maximum, capped at 1% of body weight or 1 kg a week, whichever is lower. A gain plan only offers the gentler half of that same ladder. Below that 100 kg cap, a heavier body is offered a faster safe pace than a lighter one. At or above it, everyone's maximum flattens to the same 1 kg a week.
What the estimate cannot know
These formulas describe an average person with your stats. Your number may be higher or lower. Genetics, muscle mass, and daily movement all matter, and your needs change as your weight changes. Treat the result as a starting point. Watch what happens over a few weeks, then adjust. That is the part CaloriSpy helps you do.