How do I say that something was decreased and became X times less? In a sentence like: The new file is 20K while the old file was 100K, that's a decrease in 5 times? Or: The file was 100K and it decreased by 5 times, becoming only 20K?

For instance, I found this topic where someone said:

"Decreased by 8 times" doesn't mean anything to me at all.

What are the most used and naturally sounding constructions for this types of sentences?


The other answers are correct, but the common English expression that is the actual equivalent of what you are referring to is

The file size decreased by a factor of five.


I suggest that quick and easily understood ways of saying this are

The file size decreased by 80%, from 100k to just 20k.

The file size decreased to 20% of its original size, from 100k to just 20k.

The file size decreased to one-fifth of its original size, from 100k to just 20k.

  • Is it fine and commonly used to attribute the decrease (as a noun) that happened, rather than attributing the process? I suppose "that was a (an?) 80% decrease" is fine to say. Or it's common only to use adjectives (like huge/tremendous/significant decrease) but not specific values? – Ilya Semenov Jan 29 '14 at 17:22
  • If the numbers are important, use the numbers. If you want to leave it vague, use adjectives. – StoneyB on hiatus Jan 29 '14 at 17:32

It makes sense to say that something "decreased by 80%" or "decreased by 1/3". I don't know what "decreased by 8 times" would mean. Decreased by 8 times what? When someone says that it "increased by 3 times" they mean by 3 times the original value, so if it used to be, say, 100 -- well, sometimes they mean it is now 3 times the original value, i.e. 300, other times they mean that it added 3 times the original value, so it is now 400. But "decreased by 8 times"? If it used to be 100, is it now negative 700? Possible, I guess, depending on what it is we're measuring.

It is reasonable to say that something "decreased 7 times", meaning that there were 7 occasions on which it decreased. Like, "While it looks like I got raises every year on paper, my salary has really decreased 7 times in the last 12 years if you adjust for inflation."


Indeed, if something decreases (by) a number of times, I have a hard time understanding what is meant exactly. It is a lot more informational to use a construction like:

The file size decreased by 80%.

The problem with "decreased (by) 5 times" is that nobody knows how much a one-time decrease is. In the case of your file size, it decreased to one fifth of the original size. "Decreasing 5 times" would indicate that it somehow decreased in size 5 times, first from 100 to 84 (??), and so on. But you would never say it decreased once of it went from 100 to 84, since that 1-time decrease only means "16" in case of an 80% decrease :)

  • Yeah, I figured where's the problem. Interestingly, in Russian, it's perfectly fine (and it's the most commonly used way to say!) to decrease something by X times, which means that if you increase the object back X times, it would become the original size. But the phrase only starts making sense when X > 1 (at least 1.1), a one-time decrease is meaningless as well. Go figure! – Ilya Semenov Jan 29 '14 at 17:34

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