Recommendation Letters

| General suggestions | Am I the right person? | How to ask |

(Last updated: June 2025)

Please read this page if you are considering asking me for a recommendation letter. The first section is general advice (for which I make no claims of being an expert), and the last two sections are specific advice for whether and how to ask me for a letter. I am currently a postdoc (at UIUC), and that may influence whether I am the right person to write you a letter.

Large parts of the later sections were based on a similar page of Ravi Fernando.

General suggestions

This section comes with a very strong caveat: I have never been on any admissions committee, or any other committee that reads applications. As such, it's better to view these suggestions only as a starting point, and to talk to others with more experience. Still, I include this section since what makes a good letter is relevant to the below and many students don't know anything about the question.

What makes a good recommendation letter writer?

There are several factors, including the following:

• How well the recommender knows you (number of classes you took from them, your class participation, attendance at office hours, etc.)
• Your performance in their class or research project
• How well their experience with you speaks to the strengths you're hoping to convey on your application
• How specifically the recommender can speak to these strengths
• The recommender's seniority and/or connection to what you're applying for
• The letter-writing ability and/or effort of the recommender (I include this as surely there are style differences in the way different people write letters, and the way they are perceived. In general I don't know how to guess who would write a "good" letter, and I suspect it's harder than it seems)

How important these factors are depends on what you're applying for. For applications that are relatively low-stakes, a strong performance in their class may be enough. For higher-stakes applications (e.g. graduate school, REUs), thinking closely about the other factors is a good idea. For instance, if you're applying for graduate school, asking a research mentor could be more targeted than asking an instructor. If you're applying for a high-level program, a recommendation from an advanced class will carry more weight than one from an introductory class. If you're applying for non-math programs and just want a letter saying you're competent in STEM, seniority might not matter at all, while if you're applying for a math Ph.D. program, it may be very useful to have a known expert in your area of interest. You might also think about what each letter-writer is able to write about you, and look for complementary letters. For instance, at least one person who can speak to your enthusiasm, at least one person who can speak to your skill, at least one person who is a respected professor in your favored area. At best, all your letter-writers will have all these qualities, but in practice the three most senior researchers you know likely won't also be the three people who know you best. So it's worthwhile to ask yourself: what is this person likely to be able to write about me, and are all of my strengths likely to be represented on my letters?

What to do to put the above factors in your favor

It's hard to plan for the future. But if there's a particular person you anticipate wanting to ask for a letter for in the future, you want to make their job as easy as possible. For the most part, letter-writers want to write good letters.

• Do well in their class! Different people differ in which students they will write letters for, but in general it is much easier to write a strong letter for a student who got an A than a student who got a B or lower. Furthermore, get your homework in on time, show up on time to class, etc.
• Interact with the potential recommender. Participate in class, attend office hours, ask questions. It should go without saying that it's not a good idea to do this in a cynical way: don't just go to office hours with the sole purpose of telling your instructor your name. But if you're planning to ask your instructor for a recommendation letter, presumably you're insterested in the class they're teaching. Don't be afraid to show that enthusiasm, ask questions about the homework, etc.
• (Perhaps): interact in a way that gives the recommender specifics. I am less sure about this one, and you don't want to go overboard. But I will say that even if I've had many positive interactions with a student, it can sometimes be hard to remember any specific anecdotes that would fit in a letter. Having a couple (not the majority) of your interactions be over email solves this problem. There are other things you can do too e.g. TeX up detailed notes for the class; read papers in a closely-related topic and talk to your professor about them; put a lot of effort into any class projects; etc. Again, don't waste your instructor's time and don't fake things: if you're truly interested in the topic, just let that shine through.
• (Perhaps): if you know you're going to ask for a recommendation letter at a later date, mention this in advance. This is especially true if you're years away from asking for the letter, but can be helpful for a shorter time period too. I personally find this helpful because it allows me to jot down some thoughts that I might otherwise forget. But I don't know if that's true for other people. If you do ask in advance, it's important to do this respectfully and honestly, and only if you really do expect to ask that person for a letter. (Also, in most cases you would be better off asking for letters from people you've recently interacted with, rather than an instructor you had years ago. The main exception is when a student is graduating but plans to apply to graduate school in a couple of years.)

Am I the right person to write a recommendation letter for you?

If you're applying for something relatively low-stakes (e.g. summer schools, some departmental programs), I might only be asked to attest that you're a serious student who is likely to benefit from the program. I can often make this judgment based on knowing you for less than a full semester.

Otherwise, this depends on the factors listed above. In particular, if I've known you for less than a full semester, it will be hard to write you a strong letter unless we've had extensive interactions outside of class (e.g. a research project). Similarly, it's easiest to write a strong letter if you got some flavor of A in my class (this is relaxed somewhat for higher-level classes). And even if you did well in my class, the sort of letter I can write will depend on how much you participated, whether you came to office hours, etc. If you didn't participate much, it will be hard for my letter to add much that your transcript doesn't already show. If you did well in my class, were reliable and respectful, and showed a genuine enthusiasm for the material, that makes me most likely to be able to write you a strong letter.

If I've been your research mentor, it's quite likely that I would be a good person to ask for a letter, assuming you have had strong participation in the research project. At the very least, if you talk to me, we can discuss who to ask for letters.

Even if I can write you a strong letter, it may in some situations be worth considering asking someone else for seniority reasons. (As a postdoc, I am still relatively low on the academic totem pole.) If Famous Professor X can write a letter saying that you're in the top 5% of all students they've had in the last 20 years, that will carry much more weight than me saying that you were in the top 5% of my students last year. On the flip side, you definitely shouldn't ask someone for a letter just because they're famous—a strong and detailed letter beats a lukewarm letter no matter who it's from.

If you're not sure whether I'm the right person, then feel free to ask—I'd be happy to talk through your options with you. Needless to say, it is in your best interest to have this conversation sooner rather than later.

Asking for a recommendation letter

The following information is useful for me to consult when writing my letter.  Please send it to me as early as you can (a month's notice is ideal, although it's okay if some things come later):

• Information on what you're applying to (e.g. a list of schools, or the website for a special program) and how I should submit my letter
• When my letter is due (and please remind me a few days before the deadline if I haven't submitted it yet)
• Your CV and transcript, plus (drafts of) your application statements
• Who else is writing a letter for you (so I know what will and won't be covered in their letters)
• Any particular things you'd like me to speak to in my letter. Of course, I can't guarantee I will be able to highlight these areas, but you're always welcome to ask (e.g. "do you think you know me well enough to convey my enthusiasm for the subject?")

The way many applications work is that you add your letter-writers to each of your applications, and then the system sends out an email telling us where to upload your applications. If possible, please add your letter-writers to all your applications at once. It should be possible to add your letter-writers as soon as you've stated the application, and it's much easier to get ten emails asking for the letter all at once than ten emails that trickle in over the course of weeks. Of course, you may add or remove schools from your list, and you certainly shouldn't refrain from submitting an application just because it will ping your letter-writers one more time. But to the extent that you know what you're applying for, adding the letter-writers to all applications at once makes things easier on our end.

Finally, if your application ends up being successful, I'd appreciate hearing where you got in. It's nice knowing what became of my old students, and it may help provide a point of comparison for my future rec letters (e.g. "Future Student Y reminds me of a student I once had who got into School Z...").