Key takeaway
An equation is a starting hypothesis. Your observed trend is the feedback that makes it personal.
BMR equations describe groups
The Mifflin–St Jeor equation estimates resting energy expenditure from age, height, weight and an equation profile. It cannot see lean mass, genetics, hormones, recent dieting or individual movement patterns.
Activity multipliers add uncertainty
Multipliers compress work, steps, exercise, digestion and spontaneous movement into one category. Category labels are subjective, and wearable calorie estimates also carry error.
Use the result safely
Start with the estimate, monitor two-to-four-week trends and adjust gradually. Do not force an aggressive target when the number conflicts with hunger, training, recovery or safety.
The calculator is not appropriate for everyone, including people under 18 and people with specific medical, pregnancy or eating-disorder considerations.
Use this information in context
This article is general education for adults. It is not a diagnosis, treatment plan or individualized medical nutrition advice. See the methodology and references and the nutrition disclaimer.