How this calculator works
This tool uses the Mifflin-St Jeor equation — the formula with the best research support for estimating resting metabolism — then multiplies by an activity factor. Every mainstream calculator does roughly this. The difference is what we do with the output: instead of pretending the result is exact, we show the ±10% band the formula actually earns.
Why we ask about movement and training separately
Most calculators ask one blended question: “how active are you?”, with answers like moderate — exercise 3–5 days a week. That forces a single answer out of two unrelated things. A warehouse worker who never trains and a desk worker who lifts four times a week both land on “moderate,” and neither description fits.
So we ask twice. Activity covers movement outside exercise — work, errands, getting around — anchored to step counts, because most people know roughly what their phone reports even if they can’t rank themselves on an abstract scale. Exercise covers structured training sessions, which add on top.
Being straight about what this buys: it is a clearer way to ask the question, not a more accurate equation. Self-reported activity carries a 10–20% error against doubly-labelled water however you elicit it. The gain is that each question is easier to answer honestly, and you’re not describing your training twice — which is the usual way these estimates come out high.
Why a range beats a single number
Two people with identical stats can burn hundreds of calories apart per day. Muscle mass, fidgeting, job activity, and even how accurately you log food all move your true maintenance. A single number invites false confidence; a range invites the right habit — start inside it, watch your two-week trend, and adjust in small steps.
What to do with your number
Pick the middle of your range and eat there for 14 days while logging honestly. If your weight trends the way the table above predicts, the estimate was good. If not, adjust by 100–150 kcal and repeat. That feedback loop — not the calculator — is what actually finds your TDEE.