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

A “person month” is the metric for expressing the effort (amount of time) program directors/principal investigators (PD/PIs), faculty, and other senior personnel devote to a specific project. The effort is based on the:

• Type of your appointment with the organization, such as calendar year (CY), academic year (AY), and/or summer term (SM)
• Your organization’s definition (such as defining the academic year as a 9-month or a 10-month appointment)

Conversion of effort percentage to person months is straightforward. To calculate person months:

• Multiply the percentage of your effort associated with the project by the number of months of your appointment
• If your appointment is less than full time, multiply the number of months of your appointment type by the proportion of your effort compared to a full-time equivalent (FTE). 

For example:

• 25% of a 9-month AY appointment equals 2.25 person months (9 x 0.25= 2.25)
• 10% of a 12-month CY appointment equals 1.2 person months (12 x 0.10 = 1.2)
• 35% of a 3-month SM appointment equals 1.05 person months (3 x 0.35= 1.05)
• 10% of a 0.5 FTE 12-month CY appointment equals 0.6 person months (12 x 0.5 x 0.1 = 0.6)

Another example:
If the regular pay schedule of an institution is a 9-month academic year and a 3-month summer term, and the PD/PI will devote at 30% effort during the academic year and 50% effort during the summer term to the project, then 2.7 (9 x 30% = 2.7) person months and 1.5 (3 x 50% = 1.5) person months should be listed in the academic and summer term blocks of the application budget, respectively. 

Note: For the Current and Pending (Other) Support Common Form (CPOS), individuals should report their cumulative person months, rather than separating academic year and summer term efforts, so in this example, the PD/PI would indicate 4.2 (2.7 + 1.5 = 4.2) person months on their CPOS for this project.

Additional Resource: 

• FAQs for person months