Every number on this page comes from the calculator that owns it. The page collects the measurements all five share, then hands each method the inputs it declares and shows what it returns, so a row here and the tool page it links to always agree.
BMI is weight divided by height squared. The Body Fat Estimator and the Army tape method both run the US Navy circumference equation, so they return the same percentage and differ only in the bands they read it against. FFMI and lean body mass both start from a body fat percent, which is why leaving that box blank hands them the tape estimate rather than asking you for a number this page already worked out.
All five are estimates from a scale and a tape measure. DEXA, hydrostatic weighing and BodPod measure body composition directly and none of these approaches them for accuracy. Use the direction they move over months, not any single reading.
Tips: Measure at the same time of day, on the same side of a meal, with the tape snug and level. Most of the week-to-week noise in these numbers is measurement noise, not you.
Pick the one method you will actually redo and track that one. Comparing this month's BMI against last month's Navy estimate tells you nothing.