Follow-up email to a professor: when is it time to send?

Direct answer: About two weeks after the first email, once, and only when you have something new. Queen's University advises one polite follow-up after roughly two weeks, and the reminder data below show that each further nudge recovers less than the one before it.

The graduate studies office at Queen's University advises: "Follow up once: If you don’t receive a response after ~2 weeks, it’s fine to send one polite follow-up email" (Queen's University, n.d.). The rest of the decision depends on what you can add. The table below turns the interval into a rule you can apply to your own thread. It is an editorial tool written by MAAS from the sources in this post, not a finding of any study.

Source: decision rule written by MAAS from Queen's University (n.d.) and the reminder studies below, 2026-10-27.

Direct answer: Less than you might hope, because we found no study that fixes how long a professor takes to answer a doctoral enquiry. The best-known field experiment wrote to more than 6,500 professors at 259 US universities, so cold emails to professors are a studied setting, but it was built to test bias and not to time replies.

Milkman, Akinola and Chugh (2015) had fictional applicants write to more than 6,500 professors at 259 US universities "to discuss research opportunities prior to applying to a doctoral program" (Milkman et al., 2015, p. 1678). Their question was how pay and representation shape bias, so the study does not tell you when to nudge.

A small worked example shows what this means for a shortlist. It is an illustration based on the physician-survey reminder data in the next section, not a finding about professors. Suppose you write to 12 professors and 4 reply in the first weeks. The remaining 8 are silent, so a reminder plan for 12 names is really a plan for 8, and if a reminder recovered about half as many replies as the first send did, as it did in that survey data, you would expect roughly 2 more.

Three limits apply: the applicants were fictional and asked only to discuss research, the sample came from US institutions, and the study was not designed to test reminders. For what to do when the reply does arrive, read our guide to what to ask when a professor says "send me more".

Direct answer: The best numbers come from other populations, so treat them as proxies. In 11 physician surveys, the first reminder period yielded about half the response of the first contact, and later reminders yielded 3.3% or less. In a German business survey, one late reminder raised participation by 8.9 percentage points.

No study we found measures reminders to prospective doctoral supervisors, so the figures below come from surveys of other busy professionals and are labelled as proxies. Barnhart, Reddy and Arnold (2021) analysed 11 American Board of Internal Medicine physician surveys with weekly email contacts. The response rate was 8.9% in the first period and fell by 50% to 4.4% in the second, then 3.0%, 3.3%, 2.2% and 1.9% in the periods after. The overall predicted response after six weekly contacts was 23.7%.

Source: Barnhart et al. (2021), a physician-survey proxy; the last column is MAAS arithmetic from the published rates, 2026-10-27.

Boddin, Dörner, Hong and Keusch (2026) found that sending reminders two days before the end of an online business survey in Germany raised the likelihood of taking part by 8.9 percentage points. Van Mol (2017) reached a similar conclusion in a web survey of 15,651 students at the University of Antwerp, finding that "extra reminders are effective for increasing response rates, but not for diversifying the sample" (Van Mol, 2017, p. 317). Read this as support for sending one reminder, not as proof about wording.

Direct answer: Silence is ambiguous: the message may be unread, read and set aside, or declined without a word. Evidence on email requests and on supervisors suggests that senders misjudge how an unsolicited message looks to a stranger, so a quiet inbox is better read as "not yet answered" than as "rejected".

Roghanizad and Bohns (2017) found that requesters asking strangers for help overestimated compliance, and the authors explain that "requesters, anchored on their own perspectives, fail to appreciate the suspicion, and resulting lack of empathy, with which targets view email requests from strangers" (Roghanizad & Bohns, 2017).

Henderson et al. (2025) studied the stage before a formal application through a six-week diary kept by 19 supervisors at one UK research university, followed by focus groups with 11 of them. They describe an "informal phase which precedes the submission of a formal application" (Henderson et al., 2025, p. 167) in which supervisors are "caught between their principles and values and squeeze conditions" (Henderson et al., 2025).

Goldsmith, MacKenzie and Wynter (2024) add a caution about reading silence as a verdict. They sent emails to academics at Australia's Group of Eight universities that were identical except for the fictitious student's name, and found evidence of racial bias in the responses. When identical emails get different treatment, a missing reply says something about the inbox and the reader, and not only about the application.

Direct answer: A good follow-up holds one new fact, one question answerable in a line, and the original thread underneath. New means something that changed your application, such as a finished methodology section, not a restatement of your interest, and it should be short enough to read in a single pass.

Queen's University (n.d.) says a first email should be "no longer than 250 words", and a follow-up needs less room still. A sketch of the shape, with illustrative details:

Subject: Re: Prospective PhD student interested in urban flood modelling

Dear Professor Tran, since my message of 3 November I have drafted the methodology section, now on pages 6 to 8 of the attached proposal. Would you be open to a 15-minute call to tell me whether the direction fits your group?

Source: illustrative examples written by MAAS for this guide, not study data.

Queen's University (n.d.) also tells applicants to read at least 2 to 3 of a professor's latest publications, so a follow-up can cite one of them as its new item.

Direct answer: Send one follow-up now that opens with what has changed, and treat it as your single reminder. Do not use LinkedIn as a replacement for email, because no study we found supports it and the channel gives the professor no duty to reply.

Queen's University (n.d.) sets its benchmark at roughly 2 weeks, so a thread that is 3 weeks old is already past it. A computer science applicant who wrote two weeks ago can count a short proposal summary or a link to code as news. An economics applicant who wrote three weeks ago can count a comment on a newer paper or a drafted section. Anyone who has already sent a reminder without a reply should close the name.

A message on LinkedIn after two unanswered emails can read as pursuit across platforms. The better use of the next two weeks is a batch of new names, as in our guide to finding a PhD supervisor shortlist, with the opening message shaped by the guide to the first email to a professor.

Direct answer: Admissions studies suggest a follow-up email to a professor is read beside letters, grades and programme rules, so a message that adds a new item to your file does more than one that only asks whether the first message arrived.

These studies concern selection committees and not single inboxes, so use them to decide what to put into a follow-up, not to guess why one person stayed silent. Jones et al. (2020) surveyed admission to US economics PhD programmes and found that top-25 programmes valued undergraduate programme rank and recommendation-letter strength more, so add a new referee or document if you have one. Kim et al. (2026) analysed 182,638 admissions records across 117 PhD programmes at one US flagship university and found that dropping the GRE requirement lowered acceptance rates, while applicant demographics mostly did not shift significantly. Dagenhard et al. (2016) reviewed 17 health education doctoral programmes, of which 11 required a 3.0 master's GPA, credit hours ran from 70 to 73, and all 17 required a dissertation. That significant variation is why one template sent to every professor wastes your single reminder.

Direct answer: Surveys of doctoral students describe supervision as a bundle of choice, advice and control that lasts for several years of daily work, so a follow-up email to a professor opens a working relationship and is more than a request for a quick reply.

González-Ocampo and Castelló (2019) studied 1,173 students at Spanish research universities and sorted 223 supervision experiences into five categories, one of which was supervisor choice, so say why you chose this professor. Wichmann-Hansen and Nielsen (2024) surveyed 1,243 doctoral students at one Danish university and found that advice went with more independence and control with less, yet satisfaction rose with both styles. Denis et al. (2019) interviewed 20 supervisors and 20 students from 8 faculties in North America, and difficulties followed a timeline from admission through scientific writing to employability, so name the writing support you hope for.

The PhD Application Strategy and Execution service works through your shortlist and your outreach letters with you. MAAS sends letters in batches from an academic mailbox set up in your name, tracks the replies, forwards every reply to you, and follows up on a set cadence before a target is closed out. You approve each letter before it goes, and the mailbox is handed over to you when the service ends.

The service is advisory work with no grade target and no promise of an outcome, because replies and admission stay with the professor and the committee. The PhD application guide lays out the whole timeline.