Health & Fitness Calculators

Health and fitness calculators estimate body metrics and energy needs from a few simple inputs. The common questions in this area share a small set of established equations: a body-composition index from height and weight, a resting metabolic rate from age, sex, height, and weight, and a daily energy estimate that scales that rate by how active you are. These figures give a useful starting point for understanding weight, nutrition, and activity, as long as they are read as estimates rather than exact measurements.

Every tool in this section states its equation, assumptions, and limitations clearly, and walks through a worked example so you can see exactly how the result was reached. It is important to be honest about what these numbers can and cannot do: they are screening and planning aids, not diagnoses, and an index or a calorie estimate cannot capture everything about an individual body. Treat the results as a guide and consult a qualified health professional before acting on them. For the underlying equations, see the formula reference.