What is a “Person Month” & How Do I Calculate It?

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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.

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.

 

9 Comments

    1. Since it’s a 12-month Contract you will just use the 12 months calendar formulae,
      You will use the Calendar Year (CY) where you divide your annual salary with 12 ie
      1/12 * x= Y (Your monthly salary will Y), then depending on the % of effort you use,
      multiply with the CY i.e (%* CY) then you will get CY Months, then Multiply your
      Your monthly salary and the CY months to get the budget figure for that effort.
      i.e (Y*CY Months)

  1. How would a CM be listed for a person who is .5 FTE and put 50% of that FTE on a grant/contract? Our department has 12 month faculty.

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