# How fast is one RPM on average?

I know this depends on a lot of factors but I heard a revolution can happen in 0.02 second is this the case? I can't even stop my stop watch that fast?

• Note, that it doesn't depend on a lot of factors - it only depends on one: the speed of the engine measured in RPMs. Commented May 3, 2016 at 13:57
• What, you don't have a millisecond stop watch? ;-)
– Moab
Commented May 3, 2016 at 15:57
• 1 RPM is 1 minute fast :-). If your car idles at 1,000 RPM then one rotation takes .06 seconds or 16.66666666666667 rotations per second Commented May 6, 2016 at 19:51

This is a math-only question, and no one has explained the formulas. Also I like the idea of this simple question having multiple answers so...

RPM is Revolutions Per Minute, but we want a time in seconds. When you hear that word "per" it means division. So, what we have is 4000 revolutions / 1 minute (where / is the division symbol). This easily converts to 4000 revolutions / 60 seconds. The result of that (4000/60=) is 66.66 revolutions / 1 second.

Now we have revolutions per second, but you want seconds per revolution (what we have, flipped upside down). So, simply enough, we flip the whole thing upside down to get 1 second / 66.66 revolutions, and the result is (1/66.66=) 0.015 seconds / 1 revolution.

Finally, flip that around grammatically and we get "1 revolution takes 0.015 seconds". Which is 15 milliseconds, but I'll leave that conversion as an exercise for the reader.

• Thank you for your detailed answer with a guide on how I can solve for the answer myself Commented May 3, 2016 at 14:04

In a car rpm are very often shown. From experience you might know that for a normal car it varies between 1000 and 3000 rpm for normal use cases.

3000 rpm = 50 rotations per second = 1 rotation per 0.02 seconds.

Divide the measured RPM by 60 gives the number of revolutions per second. For an engine at idle that would be about 12 revs per second. At a 7500 rpm redline it is 116 revolutions per second.

Combustion engineering is done in degrees of crankshaft rotation and milliseconds.

60 seconds. RPM stands for Revolutions Per Minute. if you have one RPM then it takes 60 seconds to do a complete revolution.

Now there are ways to convert from RPM (Revolutions Per Minute) to seconds per revolution or other such measurements as mentioned in other answers however they do not answer the actual question asked of how fast one RPM is.