How do I convert a bearing rating life in millions of revolutions into operating hours?

LILY Bearing | 2026-10-28

Best answer

Keep the units visible through the conversion

If a life value is stated in millions of revolutions, multiply by one million before dividing by the rotational rate.

A shaft running at n rpm makes 60n revolutions per hour. Dividing the total revolutions by that hourly rate gives hours. The step that most often disappears in an abbreviated worksheet is whether the original life entry means revolutions or millions of revolutions. JTEKT distinguishes these representations in its rating-life calculation guidance. This conversion changes the unit of the result, not its reliability level or engineering assumptions. It does not turn a rolling-fatigue estimate into a measured service-life value.

JTEKT: Calculation of service life

Work through a number that exposes unit mistakes

For a stated life of 120 million revolutions at a constant 600 rpm, the hourly rate is 36,000 revolutions.

The conversion is 120,000,000 / 36,000 = approximately 3,333 hours. Entering 120 instead of 120,000,000 would produce a result a million times too small. Record 600 rpm as an assumption, not as an observed speed unless it was actually measured. If the machine runs at several speeds, this single-speed conversion cannot by itself describe the entire operating history. Keep the duty segments and their durations so that the life model and time conversion can be applied consistently to the intended duty.