What is an X+Y schedule in residency? 4+1 and 6+2 explained

Chiefly’s team loads your X+Y pattern as a rule with the rest of your program’s rules and ACGME requirements, and Chiefly generates the block schedule around all of them. You send last year’s schedule and your requirements; your chiefs review drafts and stay in control.

Your chiefs can change the pattern and re-run the live schedule, for example to compare a 4+1 with a 6+2 before committing, or edit it by hand; every edit is checked against your rules.

When a resident goes on parental leave, starts off-cycle or starts late, Chiefly re-runs the schedule with your rules intact, saving every version so you can compare drafts. The resident progress dashboard tracks requirement weeks against what each PGY year requires, and flags anyone behind or at risk.

Chiefly is used by residency programs across many specialties. The Boston Combined Residency Program was moving to an X+Y model when it built its 188-resident schedule with Chiefly, and saved more than 3,600 chief and admin hours in its first eight months (case study). UVA Pediatrics built its academic year in a week and a half (case study). More on residency block schedule software.

An X+Y schedule is a residency block schedule that alternates X weeks of rotations (wards, ICU, nights, electives) with Y weeks of ambulatory time. Residents have no continuity clinic during X weeks and no inpatient duties during Y weeks (JGME, 2014). Programs also call it block scheduling.

The numbers name the cycle: a 4+1 is four weeks of rotations, then one week of clinic, and a “4-2 schedule” has two clinic weeks. The first model reported was a 4+1 (JGME, 2014), at an internal medicine program in Allentown, Pennsylvania (JGME, 2010). The most common patterns are 4+1 and 6+2, with 4+2 and 3+1 also common (Cureus, 2022).

Residency programs use X+Y to keep inpatient and clinic duties from colliding and to protect time for outpatient training. Under weekly clinic, residents leave the wards or ICU for a half-day of clinic, and the most common complaint is that clinic days feel like two full-time jobs in one duty-hour-limited day (JGIM, 2016).

In 2009 the ACGME set internal medicine minimums of 130 half-day clinic sessions over three years and required programs to reduce inpatient-outpatient tension (JGIM, 2016). Many programs read that as a nudge toward block scheduling, and the ACGME’s Educational Innovations Project, a pilot that began in 2006 with 21 internal medicine programs, helped early adopters (JGIM, 2019).

The rule still stands: the ACGME internal medicine requirements effective July 1, 2026 say rotations “must be structured to minimize conflicting inpatient and outpatient responsibilities,” and Y weeks of outpatient work count in full toward the required 10 months of outpatient experience (ACGME).

Residents are split into equal groups, or cohorts, whose clinic weeks are staggered so one group is always in clinic while the rest cover inpatient services and electives. You need (X+Y)/Y groups: five for a 4+1, three for a 4+2, four for a 6+2. Balance each group by PGY year and clinic site (JGME, 2014).

An illustrative 4+1 for five groups over 10 weeks:

Each week, one group (20% of residents) is in clinic and four staff the wards, ICU, nights and electives. Because teams draw from several groups, a whole team never rotates off at once (JGME, 2014).

A clinic week has 10 half-days to fill. At Oregon Health & Science University (OHSU), it began with a weekend off, then eight half-days of clinic and two of didactics (Medical Education, 2017).

Patients still need care during X weeks. One 4+1 program grouped one resident from each cohort into a mini-practice, with whoever was in clinic handling the others’ results and messages; task completion rose from 75% to 97% (Clinical Teacher, 2020).

For residents’ experience, usually yes; for continuity of care, the evidence is mixed. A 2019 systematic review of 11 internal medicine studies found block scheduling improved resident satisfaction, cut inpatient-outpatient conflict and added clinic time, with the biggest gains from one-week clinic blocks (JGIM, 2019).

In favor:

• More clinic. Three studies of one-week blocks found 32% to 67% more clinic sessions (JGIM, 2019).
• Fewer handoffs. UCLA neurology cut about six inpatient handoffs a week (Neurology: Education, 2022).
• Rest. At OHSU, residents slept about half an hour more a night in their clinic week than in the ICU (Medical Education, 2017).
• Program directors like it. In a national survey, 90% of internal medicine program directors using X+Y were satisfied with the switch (Cureus, 2022).

Against:

• Continuity can slip. The review found X+Y may cut how often residents see their own patients, with inconsistent effects on patient continuity, satisfaction and outcomes. In one 4+1, patients saw their own resident 63% of the time, versus 72% with weekly clinic (JGIM, 2014).
• Gaps between clinic weeks. At four institutions, 92% of residents said a handoff matters when seeing a colleague’s patient, but only 18% got one at least half the time (JGIM, 2025). When an internal medicine program in Boise moved from 6+2 to 3+1, the wait for a third-next-available appointment fell from 34.1 to 26.5 days (JGME, 2024).
• Inpatient trade-offs. Shorter rotations bring more team turnover, Y weeks can come out of electives, and swaps may be limited to residents in the same cohort (JGIM, 2016).
• Admin work. In 2015, one in five internal medicine program directors lacked the administrative resources to switch (JGIM, 2019).

Some large programs, including the University of Washington, Emory and Massachusetts General Hospital, skipped X+Y and scaled clinic to each rotation’s intensity instead; no single model suits every program (JGIM, 2016).

Internal medicine uses X+Y most, and pediatrics, combined internal medicine-pediatrics and some neurology programs use it too.

• Internal medicine. By 2015, 43% of internal medicine residencies used block scheduling (JGIM, 2019), and 62.5% of respondents to a 2015 survey of resident clinic directors used some version of X+Y (JGIM, 2016).
• Pediatrics. ACGME pediatrics rules once required clinic spread over at least 26 weeks a year, so in 2018 five programs used a pilot waiver to run full X+Y and reported better continuity and inpatient workflow (Academic Pediatrics, 2021). Current requirements call for at least 36 continuity half-days a year, with gaps that should not exceed 8 weeks (ACGME).
• Internal medicine-pediatrics. In a 2021 survey, 38% of med-peds programs had at least one partner categorical program on X+Y (Cureus, 2022).
• Neurology. UCLA moved its PGY-2 class to a 4+2 in 2020-21, and satisfaction with the outpatient experience rose from 42% to 93% (Neurology: Education, 2022).

Do the coverage math first, then form cohorts, build an anonymous template around your highest-priority services, and add names last. Planning ideally takes a year, and almost all programs switch at the start of an academic year (JGME, 2014).

1. Do the coverage math. With N residents on the pattern, N × X/(X+Y) are on rotations each week: 60 residents on a 4+1 leave 48 for services and send 12 to clinic. Run it per PGY year against every service’s staffing minimum and your clinic’s capacity.
2. Form balanced cohorts. Make (X+Y)/Y groups, balanced by PGY year and clinic site. Off-service rotators, tracks and combined programs also shape the choice of X and Y (JGME, 2014).
3. Fit rotations to the cycle. Four-week rotations don’t fit a three-week X, and some programs use two-week rotations (Cureus, 2022). Staggered cohorts switch on different weeks, so check where off-service rotators’ blocks begin.
4. Fit nights and ICU inside X. Under the current requirements, internal medicine residents can have at most two months of night float a year, four in total and one in a row, and two to six months of critical care. Continuity clinic can’t go in the transition hours after a 24-hour shift (ACGME). See our ACGME duty hour rules for 2026.
5. Fill stable teams first. Place rotations that need a consistent team, then electives and vacation, with counters to flag holes (JGME, 2014).
6. Plan for leave and off-cycle residents. A late start, an off-cycle resident or parental leave pulls someone out of their cohort’s rhythm. Decide which cohort they join, then recheck coverage and their clinic weeks.
7. Book clinic early. Set resident clinic schedules three to six months ahead so follow-ups land with the same resident (Cureus, 2022).

For the full process, see how chief residents build the block schedule, step by step.