How Do You Convert Percent Effort into Person Months?


To convert percent effort to 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)

Keep in mind that you can include up to two decimal places to report partial months in the SF424 (R&R) budget for competing applications. However, person months reported in the Research Performance Progress Report (RPPR) should be reported in whole numbers (1-12), rounded to the nearest whole person month; e.g., 1.6 person months would be entered as 2 person months.

For more information, visit our frequently asked question page on usage of person months.


  1. How should less than full time calendar month appointments be represented? For instance if a PI has a a half-time calendar month appointment and intends to work 50% of that half time appointment on a grant should the calendar months be represented as 6 months (works all year, half of that time on this grant) with a note on the justification that the appointment is part-time? Or should the calendar months be listed as 3 with no note on justification about the part-time appointment?

    1. Reflect the number of calendar months actually applied to the grant with the assumption that 12 calendar months is working full time all year. So, a person with a half-time calendar month appointment who spends half that appointment on a grant would list 3 calendar months. If the person in question is listed in the Sr/Key section of the budget and the base salary provided does not reflect a full time appointment, you may want to provide an explanation in the budget justification for your funds requested calculation.

  2. If a PI devoted 0.6 calendar months to a project should that be rounded up to 1 calendar month and included on the RPPR all personnel report? Or should it be left off completely?

    1. Apologies, I should have asked about anyone other than the PI as the instructions do address the PD/PI. To clarify my question, if a postdoc worked >.5 person months should that be rounded up to 1 person month and included on the All Personnel report. Or because the instructions say “each person who has worked at least one person month” does that mean only to include them on the report after they’ve worked “at least” 1 whole month?

  3. How should Graduate students be reported and proposed? Many times they are proposed at 12 Person Months but have a 0.25 FTE due to restrictions as they are also students. I have understood that the proposals should more likely reflect 3.0 Person Months as given in these examples. I have run into multiple issues on the RPPR side as I have been reporting a 100% 0.25 FTE Grad student as 3 Person months, but since it doesn’t align with the budgeted 12 months, I have received questions about the FTE commitment level on our grants. This was particularly problematic with supplemental grant awards (diversity supplement) that were restricted for the supplement only.

  4. hi
    i was working about 1/5-2 years out of 3/5 years on my thesis. how could I calculate this? in this time i didn’t have any theoretical unit

  5. If your project lasts for 2 years (24 months), do you calculate as 50% x 24 or you still multiply by 12? Also, can the PM calculated at different organizations be added together and presented as total PM.

  6. If a person’s yearly salary is $160,000 and will be working on an NIH project at 80% effort on an 8 month project (6.4 calendar months) then the salary will be = 160,000 /12: $13,333, x 8 = 106,666 x 0.8 = $85,333, is this correct?

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