What is a “Person Month” & How Do I Calculate It? | NIH Extramural Nexus

A “person month” is the metric for expressing the effort (amount of time) principal investigators (PIs), faculty and other senior personnel devote to a specific project. The effort is based on the type of appointment of the individual with the organization; e.g., calendar year (CY), academic year (AY), and/or summer term (SM); and the organization’s definition of such. For instance, some institutions define the academic year as a 9-month appointment while others define it as a 10-month appointment.

Source: What is a “Person Month” & How Do I Calculate It? | NIH Extramural Nexus

Conversion of percentage of effort to person months is straight-forward. 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 0.25= 2.25)

10% of a 12 month calendar appointment equals 1.2 (CY) person months (12 x 0.10 = 1.2)

35% of a 3 month summer term appointment equals 1.05 (SM) person months (3 x 0.35= 1.05)

10% of a 0.5 FTE 12 month appointment equals 0.6 (CY) person months (12 x .5 X .1 = 0.6)
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)

An Excel-based Percent of Time & Effort to Person Months Calculator is available on grants.nih.gov.

Have additional questions related to NIH’s usage of “person months”? Visit our page of frequently asked questions (FAQs) on this topic.