NIH Person-Months, Effort, and Salary in Grant Budgets: A Plain-Language Guide

Why Person-Months Confuse Even Experienced PIs

NIH switched from percent effort to person-months in 2001, and the conversion has never felt entirely natural to researchers whose whole professional identity is organized around the academic calendar. A university employs you for nine months a year. You work for twelve. Your summer salary comes from a separate pool. When NIH asks you to state how many person-months you'll commit to a five-year R01, you're being asked to translate a fuzzy professional reality into a number that will appear on a federal form reviewed by a program officer, a grants management specialist, and possibly an auditor.

The underlying reason for the switch was good. Percent effort obscured real costs because salaries vary widely: 10% effort from a highly paid senior investigator and 10% from a junior postdoc represent very different dollar amounts and very different amounts of actual time. Person-months make both the time commitment and the cost more transparent. That's useful for NIH. It also creates a system where small arithmetic errors compound into compliance problems if left uncorrected across a multi-year award.

This guide isn't about discouraging you from asking for effort — it's about making sure the effort you request is correctly calculated, honestly represents your plans, and can survive the scrutiny of a Just-in-Time review or an ongoing grant audit.

The Three Types: Calendar, Academic, and Summer Months

NIH recognizes three appointment types, and which one applies to you depends on your institutional appointment — not what you personally think your working schedule looks like.

The key rule: you can mix appointment types when the same person holds different appointments in a given year, but the total effort across all sources — all grants, all appointments — cannot exceed 100%. This is the constraint that catches people, especially when they're listed as key personnel on multiple concurrent awards.

Your sponsored programs office will know your appointment type. If you're unsure, check before you budget. Getting it wrong creates a discrepancy between what you requested and what your institution can actually certify when NIH follows up at Just-in-Time or during a site visit.

Minimum Effort: What NIH Actually Requires

NIH's general guidance is that the PI must devote sufficient effort to ensure the scientific integrity of the project. That phrase sounds vague, but program officers interpret it consistently: for most R01s, anything below 1.0 calendar month per year (roughly 8%) raises questions. Some institutes have informal expectations as high as 20%; others are comfortable with 1.2 months if the application's approach is clearly achievable at that level of engagement.

The honest answer is that there's no universal minimum published in a NOT-OD notice that applies to all activity codes. What there is: the funding opportunity announcement (FOA) sometimes specifies a minimum, and the NIH Grants Policy Statement describes the PI's responsibility to ensure scientific direction. If the FOA is silent on the matter and your program officer hasn't told you otherwise, aiming for at least 1.2 to 2.4 calendar months per year is generally safe for a single-PI R01. Anything below 1.0 will invite scrutiny.

For K awards, the minimum effort requirements are more explicit and generally higher — many K mechanisms require 75% protected time. K awardees who also carry R01 effort need to ensure their combined commitments don't push total effort above 100%, which is a surprisingly common error as a K award year overlaps with a new R01 start.

The NIH Salary Cap: How to Calculate What You Can Charge

NIH sets an annual limit on the rate of pay charged to NIH grants for senior/key personnel, tied to the Executive Pay Schedule. This is the salary cap — sometimes called the legislative salary cap — and it's updated each fiscal year via a NOT-OD notice. NIH publishes the current cap at grants.nih.gov; always verify against the most recent notice rather than using a prior year's figure, because the cap does change.

The calculation works like this: if your institution's annual base salary exceeds the NIH cap, you may only charge the cap rate to the grant. Your institution may or may not make up the difference from other sources — that's an institutional decision, not an NIH one. What NIH won't do is pay above the cap, regardless of your actual salary.

The per-person-month charge is straightforward: cap ÷ 12 for calendar months, cap ÷ 9 for academic months per academic-year month, cap ÷ 3 for each summer month (for 9-month appointments). If you're budgeting for a senior co-investigator whose salary you don't know precisely, it's reasonable to budget at the cap level and let the negotiation sort out the actual charge — as long as you're transparent about that assumption in the budget justification.

Common Errors That Trigger Budget Scrutiny

Staying Compliant After the Award Starts

Effort commitments in the funded application are not just targets — they become binding commitments that your institution certifies in effort reports. If actual effort during a project year falls significantly below what was budgeted, you may need to rebudget, reduce the charge to the grant, or document the change. NIH's standard threshold is that any change of 25% or more in committed effort for senior/key personnel requires prior approval from the NIH Grants Management Specialist.

The practical implication: don't budget for effort you know you won't actually spend. A post-award effort reduction of 30% — say, from 3.0 CMs to 2.0 CMs because another project came in and absorbed your time — isn't necessarily catastrophic, but it requires a prior approval request, a budget modification, and documentation. It's much less painful to budget conservatively up front than to manage the compliance process later.

It's also worth noting that effort reporting requirements extend to all senior/key personnel listed in the award, not just the PI. A co-investigator who is named in the award at 1.8 CMs per year but who has since moved institutions, changed research focus, or taken on administrative roles that preclude that commitment needs to be updated via a change-in-key-personnel request. Don't let stale personnel commitments accumulate across a five-year award period.

Frequently Asked Questions