Can you write me a recommendation letter?

Writing letters for students is among the most important parts of my job, and seeing students succeed in the next chapter of their career is deeply rewarding.

However, writing a good letter takes a lot of time – writing a thoughtful recommendation letter for PhD applications takes 4 hours on average, while writing a supporting letter for PhD dissertation awards can take up to several days, modulo the time spent on reading the dissertation. The time is mostly spent on thinking about your work and making a strong case for you that is fair and makes you competitive for the programs you are applying for. I often get multiple letter requests during the application season especially when close to the deadline. In the last seven years (2018-2025), I wrote 240 letters for students in total.

So, here is what you need to know when asking me for a letter.

• Please ask for letters at least two weeks before they are due. While sometimes I can finish the letter sooner, it allows me to manage time around travel, paper deadlines, and service obligations. Writing a thoughtful, substantive letter requires a free, quiet period of time and is hard to do in a rush. If you ask me to write a letter at the last minute, I would not be able to write a useful one.
• Please send me your statements and other application materials, and also let me know the information of the program. I need to understand your work broadly to be able to put up a strong letter and I will need to understand the program to be able to know how to pitch your application in the best way that can help you.
• You do not need to draft the letter. I will write my own letter. I know that in some academic systems the students write the letter and the professors sign their names. I don’t do that and I treat my letter seriously. The exceptions are green card letters; they are supposed to be written in specific languages and oftentime the lawyers draft the letters, and I review and revise them.
• You can coach me. Feel free to let me know what you want me to emphasize in the letter and how my letter would potentially help you. It is important to have letter writers comment on different aspects to show your full package. If you are not a student in my group, re-introduce yourself and tell me the work you do (I know you already did).
• No thank-you gift. This is to make clear to your letter recipients that my words are based on your deeds, no gifts. If you are grateful for the letter, work hard and do well wherever you go! In that way, the letter I wrote for the next student will have more weight and credibility.
• Last but not the least, after you've been out in the world a while, let me know how you are doing! I'd love to hear from you. Share the exciting things you're up to, and also share any ideas you have about new things we should be teaching.

Note. I am acutely aware of how important your letters are. Sometimes – especially during December's heavy season of PhD and faculty applications – I may submit letters after the deadline listed for applicants. (I understand that fellowship deadlines are mostly firm.) If the applicant deadline is between 11/16 and 12/15, I may submit your letter by 12/24. If the applicant deadline is between 12/16 and 1/15, I may submit your letter by 1/24. My colleagues and I have written hundreds of student recommendation letters; this has never caused a problem (see my X post). Feel free to email me one reminder 2-3 days before your deadlines.

1. “I am a student in your class, can you write me a letter for my PhD applications?”

Yes. I am always happy to.

On the other hand, PhD applications will largely evaluate you based on your research potential. So, a letter that comments on your research experience is typically more useful than a letter that comments on your course grades. And, there is no evidence that GPAs are strongly correlated with research potentials. So, if you only took my course (e.g., CS 423) and had a good GPA, my letter may not be very useful to you. My personal suggestion is to prioritize letters that can comment on your research skills or potentials.

If you took my research-oriented courses (e.g., CS 523 and CS 598), then you were already doing (mini) research projects during the course and I have more to comment on.

2. “Can you write me a strong letter of recommendation?”

I see what you are hinting. If I agree to write a letter, I always try my best to promote students. Therefore, the hint is unnecessary. However, I have to fairly comment on your work and my experience working with you, instead of saying something untrue or insincere.

3. “Sorry for the last-minute request, but I have an imminent deadline – can you write me a letter in 2 days?”

Sorry. I may not be able to, and even if I do, a rushed letter is unlikely to be useful, if not harmful. Please see the first bullet point in the first page.

4. “I never worked with you on any research projects. Can I ask for a letter?”

You don’t have to work with me to ask for a letter. In fact, over the years, I wrote more letters for students and junior colleagues who I never worked with than my own students.

On the other hand, for the letters to be useful, I will have to know your work well; otherwise there is not much I could say about your work or you as a researcher. Typically, the interactions take place through lab discussions, seminars, thesis committee, teaching assistant, etc.

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This document is largely inspired by Professor Scott Klemmer whom I asked for a letter and I strictly followed his requirements :)