# Unit of blower speed

I want to know whether the international unit of blower speed is RPM or r/min. I konw ther're the same, but I'm not sure which one is more prevailing internationally. Thanks for answering.

• Technically, $min^-1$ would be SI.
– towe
Commented May 13, 2022 at 5:52

Both are understood, so use whichever.

There is a joke about disk access rates being in furlongs per fortnight

The SI unit of rotational velocity is based on the radian as the unit of angular distance and time in seconds leading to:

But common and well understood units are also used: revolutions per second or per minute or per hour,

as well as radians per minute or hour depending on the quantity being measured.

No need to use a number with 3 decimal places to record in revs/hour when revs/sec may give an "easier" number...

If something rotates at 10 revs/hr then recorded as revs/sec it becomes 0.00277778 revs/sec. may be easier to stay with revs/hr....

If the question is "what is the SI unit of rotation rate", then @SolarMike is right: radians per second. On the other hand, if the question is "what is the correct ISO notation for revolutions per minute", then it's $$\,\mathsf{r}/\,\mathsf{min}$$

It depends on what you mean by "speed". Is that radians per second, as the rate at which the blower is rotating, or do you mean cubic metres per second, as the amount of fluid that the blower is moving?