Person Months Calculator: Convert Percent Effort to Calendar, Academic, and Summer Months
One calendar month is 8.33% of a 12-month appointment. One academic month is 11.1% of a 9-month appointment, and one summer month is 33.3% of the summer term.
Estimates for planning. Your institution's rates, policies, and the sponsor's terms govern.
Why sponsors use person months
NIH and other federal sponsors ask for effort in person months rather than percentages, because appointments differ. Ten percent of a 12-month research scientist and ten percent of a 9-month faculty member are different amounts of time, and person months make that explicit.
Person months appear on the budget, the senior/key personnel profiles, Other Support, and progress reports, so the figure you choose at proposal time follows the award through reporting and effort certification.
Common conversions
| Percent effort | 12-month appointment | 9-month academic year | 3-month summer |
|---|---|---|---|
| 5% | 0.6 calendar months | 0.45 academic months | 0.15 summer months |
| 10% | 1.2 calendar months | 0.9 academic months | 0.3 summer months |
| 25% | 3.0 calendar months | 2.25 academic months | 0.75 summer months |
| 50% | 6.0 calendar months | 4.5 academic months | 1.5 summer months |
| 100% | 12.0 calendar months | 9.0 academic months | 3.0 summer months |
Worked example
A faculty member on a 9-month appointment commits 10% of the academic year and one full summer month to a project. Academic months are 0.10 × 9 = 0.9. Summer months are 1.0, which is 33.3% of the summer term. Total effort on the project is 1.9 person months, entered as 0.9 academic and 1.0 summer months.
Mistakes to avoid
- Reporting calendar months for a 9-month faculty member. Use academic and summer months for 9-month appointments.
- Committing more total effort across all awards than the person has. Total person months across every active and pending award cannot exceed 12.
- Letting proposal effort drift from what payroll and effort certifications show. They must reconcile at reporting time.
Frequently asked questions
How do you calculate person months?
Multiply the percent of effort by the number of months in the appointment. For a 12-month appointment, 20% effort is 0.20 × 12 = 2.4 calendar months. For 9-month faculty, multiply academic-year effort by 9 and summer effort by 3.
How many person months is 10% effort?
1.2 calendar months on a 12-month appointment, or 0.9 academic months on a 9-month academic-year appointment.
What is the difference between calendar, academic, and summer months?
Calendar months apply to 12-month appointments. Academic months cover the 9-month academic year, and summer months cover the remaining 3 months, for faculty on 9-month appointments.
Can effort be listed in percent instead?
NIH requires person months on its forms. Many institutions track effort internally in percent, so convert carefully and keep the two consistent.
Track budgets and effort in GrantsManager
Keep salary, effort, spending, and deadlines for every award in one place, shared by PIs and research administrators.
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