# What's the difference between "a year", "per year" and "out of a year"?

Suppose I want to say that I'm at sea seven months out of twelve. (Just an example.)

I think I can say

"I'm at sea 7 months a year"

or

"I'm at sea 7 months per year"

or

"I'm at sea 7 months out of a year"

and in all three cases I would be correct. (Again, I think, feel free to correct me!) But what's the difference? And which one would be the more appropriate?

• Actually, all three are incorrect, as you wanted to say you're at sea eight months out of twelve, not seven :-) Ignoring that silly mistake, the first two are the same, IMO, although "per year" sounds more formal than "a year". Even more formal would be "per annum". "out of a year" feels a bit odd to me, and I would avoid it. It could be changed to "7 months out of 12", and that would be fine. Jul 24, 2013 at 9:21
• I agree largely with @PhilMJones, but would add that all 3 options are slightly ambiguous as to whether you are referring to a calendar year (Jan - Dec) or just to any 12-month period. Personally I think "a year" is most likely to be understood as meaning any 12-month period, whereas the 'more formal' "per year" and "out of a year" are more likely to imply a calendar year. Of course, as Phil suggested, you could just say "7 months out of 12". Jul 24, 2013 at 12:39
• I am curious: why not make these responses as answers instead of comments? I think you answer the question perfectly: all three are basically equivalent, with the only additional necessary information being whether it's 7 months out of any 12-month period or out of a calendar year.
– Dave
Jul 24, 2013 at 18:56
• @PhilMJones Fixed! Out of a year feels odd to me as well, but I've seen this expression more than once (although not often), so I included it. Jul 24, 2013 at 20:04