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Comparing Popular Research Project Grants—R01, R03, or R21

This page discusses the NIH standard independent R01 grant as well as the potential benefits and drawbacks of the small grant (R03) and exploratory/developmental research grant (R21).

These are three popular types of Research Projects (R). For other kinds of grants, see Types of Funding Opportunities.

We strongly advise you to contact an NIH program officer before you start to develop your application. He or she can advise you on whether your proposed project is appropriate for a particular grant type. The information provided here can help inform that discussion.

Is R01 Right for You?

An R01 is a mature award that gives you four or five years of independent support, enough money (as well as time) to complete a project, publish results, and start writing your next application in time to get an award before the funding ends.

If you have preliminary data, we recommend an R01. For more on qualifying for an R01, see Determine Eligibility for NIAID Grants.

Even for New Investigators, an R01 is usually the right choice—here's why:

  • Reviewer expectations are lower: they look for fewer preliminary data, resources, and publications than they do from more established R01 applicants.
  • If you qualify as an NIH new investigator, you benefit from a more liberal payline for R01 applications, so it's easier to get funded. Since FY 2006, NIAID has consistently offered a favorable payline for new R01 investigators compared to other investigators.
  • Your R01 application has a better chance of qualifying for an R56-Bridge award or selective pay if it does not succeed.
  • Though reviewers focus less on track record than they would for an established PI, you still need to propose an important problem and use a sound research approach, a topic we cover at Know Your Audience and Write Your Research Plan.

At NIAID, applications that score near the payline are candidates for R56-Bridge awards, which can act as a springboard to an R01 by giving you one year of funding so you can gather preliminary data to improve your application.

Note: we nominate programmatically important R01 applications for a Bridge award or selective pay; you cannot apply—read more in the NIAID R56-Bridge Award SOP.

Drawbacks for Smaller Awards (R21, R03)

If a small award will be your only funding, get more advice before going this route.

If you're not ready for an R01, you might think about considering a two-year exploratory/developmental research grant (R21) or small grant (R03), but first, be aware of the caveats.

These awards are primarily for established investigators who want to complete a limited project, for example, a pilot or feasibility study.

NIH did not design them to help you establish a research career.

Nor are these smaller awards easy to get. Read more at "By the Numbers" below.

While they do help some investigators, there is no evidence they create a path to independent research.

If a small award will be your only funding, get more advice before going this route.

For more details and advice, read "Should You Apply for an R21?" below.

R03 Is Small

Don't let the word "small" fool you into thinking that an R03 is especially easy to get. It's not.

Like any other grant, your application will have stiff competition, will undergo peer review, and must be suitable for the activity code.

Your project must be tightly focused, able to be completed in two years, and manageable on a maximum of $100,000 in direct costs over the two-year period. If your project doesn’t meet these criteria, it’s not likely to be well received by reviewers.

Examples of projects that fit the R03 purpose include

  • Pilot or feasibility studies
  • Secondary analysis of existing data
  • Small, self-contained research projects
  • Development of research methodology or new research technology

To see the types of projects that have been funded, go to NIH RePORTER and select R03 in the Activity Code field.

By the Numbers

If you want to use numbers to gauge the ease or difficulty of getting an R03 or R21:

To learn about paylines, see Paylines and Funding.

New Investigators: R03 Might Not Be Your Best Option

At first glance, the R03 seems well suited to a new investigator. You can request up to $50,000 a year in direct costs and do not need preliminary data. And for someone who's never written a grant application, the shorter six-page Research Strategy (versus 12 pages for an R01) might be appealing.

Given all this, you may be tempted, but you should think twice. The smaller page limit means you need a concise, tightly focused research plan. The short award and the limited budget mean you have little room for course correction. Finally, R03 awards are not renewable.

Unless your project is perfectly suited for an R03, and if you have sufficient preliminary data, you're likely better off focusing on crafting and submitting a competitive application for an R01. See our explanation above at Is R01 Right for You?

When applying for their first independent NIH research grant, new and early-stage investigators get some breaks such as a higher R01 payline.  Read more for New Investigators.

Should You Apply for an R21?

Exploratory/developmental grants fund investigators who seek to develop new ideas, models, tools, agents, or technologies, and they are also used to fund smaller projects than would be appropriate for an R01. Many investigators find success using R21s to pursue one or two Specific Aims from an unsuccessful R01 application. Here we lay out some considerations you'll want to pay attention to if you're thinking about submitting an R21. 

R21 Pros and Cons

If you’ve been thinking about submitting an R21, you’ll want to know the pros and cons.

R21s can serve different purposes for different types of research and career stages. But they’re not for everyone, and knowing the caveats will help you decide whether an R21 is a good option for you.

Starting with the reasons to apply for an R21, people use them for at least three purposes. The first one follows NIH's definition to encourage exploratory and even high-risk research:

“ introduce novel scientific ideas, model systems, tools, agents, targets, and technologies that have the potential to substantially advance biomedical research.”

The second purpose is for more mainstream applications with projects that are smaller than would be appropriate for an R01.

And the third purpose is for investigators seeking funds to generate preliminary data for a future R01 (we discuss that topic in detail in the next section).

While any one of those approaches may be appealing, consider the drawbacks.

If you're applying for an R21 to gather preliminary data, you will not have an easy time getting funded, as you'll read below. Even if you do succeed, you could end up coming up short for time with a two-year grant.

Time May Not Be on Your Side for an R21

People often find that a two-year grant is not long enough to complete a project that yields enough data for publication or preliminary data for an R01 application. To avoid a funding gap, you'll need to plan how to continue supporting your research if your R21 funds run out before a future R01 can begin.

Applying successfully for your follow-on R01 can take longer than you may think.

It typically takes between 8 and 20 months from application to award depending on several factors, including the weightiest: whether you will need to resubmit. If you end up on the long end of that continuum, your R21, which you can’t renew, may end well before we could fund your R01. For more information, see Illustrated Application and Grant Timelines.

If you’re a new or early-stage investigator, you’ll need to pay particular attention to timing issues.

While you work on your R21, time will march on, moving you closer to the end of the 10-year period when you qualify as an early-stage investigator.

Further, your R21 won't benefit from our higher R01 payline for new (including early-stage) investigators. Your R21 application will also not be eligible for our R56-Bridge award or selective pay programs.

Despite these hitches, R21s can be a useful part of a grant portfolio.  

Know the Importance of Preliminary Data for R21

Preliminary data are not required for an R21 application, but they correlate with funding success.

In 2012, we randomly selected and reviewed 200 scored R21 applications (roughly 25 percent of scored 2011 R21 applications assigned to NIAID), counting resubmissions once, to assess the presence or absence of preliminary data. To count as having preliminary data, the application had to include actual data, not just a reference to earlier studies.

Starting with the big picture, our cohort had the following characteristics:

  • We funded 59 applications for a success rate of 29.5 percent. (Note: this success rate differs from the 14.5 percent shown on NIH's RePORT site, which includes both scored and not discussed applications in the denominator.)
  • Thirteen applications (6.5 percent) had no preliminary data.
    • Of the 59 funded applications, 1 (1.7 percent) lacked preliminary data.
    • Of the 141 unfunded applications, 12 (8.5 percent) lacked preliminary data.

These data show that people overwhelmingly (93.5 percent) describe preliminary data in their R21 applications.

We don't know why. Perhaps they believe that, regardless of requirements, preliminary studies strengthen their case, or they are meeting reviewers' expectations.

Whatever the rationale, the behavior speaks for itself. And that behavior is supported by the differential success rates shown in the bullets above.

More Caution for New Investigators on R21

NIH did not intend the R21 to be a means for new investigators to obtain their first NIH grant, and there is no evidence that R21s provide a path to an independent research career. So should a new investigator apply for an R21?

Be aware that, even though NIH does not require preliminary data for R21s, most applications include it, and reviewers tend to expect it.

In 2012, we looked at the fate of new investigators submitting an R21 application and the relationship between preliminary data and success. (Note that officially NIH new investigator status—never funded with an R01 equivalent grant—applies only to R01s; we are using it here as an analysis factor only.)

First observation: the R21 is popular with new PIs.

In our 200-application cohort, 69 (34.5 percent) of scored applications were from PIs (or sets of investigators) that qualified as an NIH new investigator.

In data from another study that included unscored applications from new PIs, that number was 50 percent. For the sake of comparison, NIH 2010 data show that new investigators submitted 31.8 percent of competing R01 applications.

But closer scrutiny reveals a negative for new PIs: in our R21 cohort, success rates were considerably lower.

  • Of the 69 new investigator applications, we funded 13, a success rate of 18.8 percent.
  • Of 131 applications from non-new PIs, we funded 46, a success rate 35.1 percent.

Was the absence of preliminary data a significant factor?

Though the numbers are small, a greater proportion of applications from new PIs lacked preliminary data, compared to the cohort as a whole. Out of the 13 applications that had no preliminary data, 7 (53.8 percent) were from new investigators, none of which were funded.

Our comparison of success rates is particularly salient because it counters a belief among some new investigators that seeking an R21 as a first grant is an easier route than applying for an R01.

In fact, R01s are a better choice for a first independent grant. You benefit from a special payline for new investigators, and the R01 is a more robust award.

For a comparison of several key characteristics of R21s compared to R01s, see R21 or R01? below.

Does a Multiple PI R21 Application Make a Difference?

In our cohort of 200 applications, 47 (23.5 percent) were from multiple PIs, and they did roughly as well as single PI applications.

  • Of the 47 multiple PI applications, we funded 14, a success rate of 29.8 percent.
  • Of the 153 single PI applications, we funded 45, a success rate of 29.4 percent.

Next we looked at the effect of new versus experienced investigators on a multiple PI application's success. Though the numbers are very small, the presence of one or more experienced investigators had a positive impact.

  • For applications with all new PIs, we funded 1 of 10 applications, a success rate of 10 percent.
  • For applications that were mixed (one or more but not all PIs were new), we funded 4 of 17 applications, a success rate of 23.5 percent.
  • For applications where no PIs were new, we funded 9 of 20 applications, a success rate of 45 percent.

For this group, the effect of preliminary data is hard to determine because only four multiple PI applications did not have preliminary data, none of which were funded.

R21 or R01?

This table compares some features of the parent R21 and R01 announcements. Note that institutes may publish their own funding opportunities using the R21 or R01 with different characteristics.

Characteristic Parent R21 Parent R01

To introduce novel scientific ideas, model systems, tools, agents, targets, and technologies that have the potential to substantially advance biomedical research.

To support a discrete, specified, circumscribed an area representing the investigator's specific interest and competencies, based on NIH's mission.


Up to two years.

Up to five years.


Up to $275,000 in direct costs over two years. At most $200,000 for any year.

Unlimited. (But note that most new investigators submit a modular grant of $250,000 or less.)



Yes, as a renewal application.

Preliminary data

Not required, but read Know the Importance of Preliminary Data for R21.



For a list of participating institutes and centers (ICs), see the parent R21 announcements on our Funding Opportunity Announcements page.

Most NIH ICs. For a list of participating ICs, see the parent R01 announcements on our Funding Opportunity Announcements  page.

New Investigator benefits



Higher payline than non-new PIs, lower reviewer expectations, and other benefits.

NIAID success rate for FY 2015*

20.9 percent

18.6 percent

* Data come from RePORT's Research Project Success Rates for NIAID.


No matter which grant you apply for, you need to consider where your support will come from should you have a funding gap while you apply for and wait to receive a future R01. Read more in Approaches for Staying Funded.

To find information about different activity codes, go to our Types of Funding Opportunities page.

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