We periodically receive questions on evaluation, as well as related topics such as reporting issues. Here’s an exchange that we thought would be useful to a wider audience:

Question: I’m working on my annual report for my National Science Foundation grant, and they are asking for personnel time spent in “person months.” How do I calculate this?

A. Most federal grants these days ask you to report hours spent on grant work in this format. The formula takes into account whether a granted funded employee is on a calendar year (12 month), academic year (9 month), or summer term (3 month) schedule. Presumably, the reason for using this metric is to provide a consistent picture of percent of effort rather than just a straight number of hours spent on a project.

The National Institute of Health and the Centers for Disease Control provide the following formula:

*“To calculate person months, multiply the percentage of your effort associated with the project times the number of months of your appointment. For example:*

*25% of a 9 month academic year appointment equals 2.25 (AY) person months (9 x .25= 2.25)*

*10% of a 12 month calendar appointment equals 1.2 (CY) person months (12 x .10 = 1.2)*

*35% of a 3 month summer term appointment equals 1.05 (SM) person months (3 x .35= 1.05)*

*Another example:*

*If the regular pay schedule of an institution is a 9 month academic year and the PI will devote 9 months at 30% time/effort and 3 months summer term at 30% time/effort to the project, then 2.7 academic months and .9 summer months should be listed in the academic and summer term blocks of the application (9 x 30% = 2.7 person months; 3 x 30%= .9)”*

The easiest way to calculate person-months, however, is courtesy of Rutgers University, which provides an online tool that does the calculation for you here.

And since you asked specifically about an NSF grant, note that their report system requires that you round off to the nearest whole number.