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Week Numbers 2027: Week 1 Starts Jan. 4, 2027 Has 52 Weeks, and Free Printable Calendars With Week Numbers

Week 1 of 2027 starts Monday, Jan. 4 under the international standard, and the year has 52 weeks. Full week list, the U.S. system and four printables.

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Published 4 min read

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Week numbers 2027: calendar cards for week 1 starting Jan. 4, 2027 and week 52 starting Dec. 27, 2027, with a 52 weeks badge
Under the ISO 8601 standard, week 1 of 2027 runs from Monday, Jan. 4 to Sunday, Jan. 10, and the last week, week 52, starts Dec. 27. Illustration: Fresh Calendars

Free printable downloads

Every template is free, needs no sign-up and prints on US Letter paper. Choose PDF for printing or PNG for screens and documents.

Week number printables

  • 2027 calendar with week numbers printable: ISO 8601 weeks 1 to 52 beside each Monday-start week, federal holidays shaded

    2027 Calendar With Week Numbers

    All 12 months of 2027 on one page, Monday start, with the ISO week number beside every week and U.S. federal holidays shaded.

    PDF · 1 page · US Letter

    Download PDFPNG
  • 2027 week numbers list printable showing weeks W01 to W52 with Monday and Sunday dates and quarters

    2027 Week Numbers List

    Every ISO week of 2027 from W01 to W52 with its Monday and Sunday dates, quarter and any federal holiday that week.

    PDF · 1 page · US Letter

    Download PDFPNG
  • 2027 calendar with U.S. week numbers printable: Sunday-start weeks numbered 1 to 53, week 1 holding Jan. 1

    2027 Calendar With U.S. Week Numbers

    Sunday-start 2027 calendar numbered the U.S. way, where week 1 is the week of Jan. 1. Matches Excel's default WEEKNUM.

    PDF · 1 page · US Letter

    Download PDFPNG
  • 2026 calendar with week numbers printable: ISO weeks 1 to 53, Monday start, with U.S. federal holidays shaded

    2026 Calendar With Week Numbers

    The rest of this year at a glance: 2026 with ISO week numbers, including the rare week 53 that ends on Jan. 3, 2027.

    PDF · 1 page · US Letter

    Download PDFPNG
In this article
  1. What week is it today?
  2. How ISO week numbers work
  3. The U.S. system gives different numbers
  4. 2027 week numbers by month
  5. Week numbers of 2027 holidays
  6. Week numbers in Excel and Google Sheets
  7. Planning with week numbers

Week 1 of 2027 starts on Monday, Jan. 4, and the year has 52 weeks under the International Organization for Standardization (ISO) date standard, ISO 8601. The first three days of January are left over from 2026: Friday, Jan. 1 through Sunday, Jan. 3 are part of week 53 of 2026. The final week, week 52, starts on Monday, Dec. 27, 2027 and ends on Sunday, Jan. 2, 2028.

What week is it today?

Sunday, Oct. 18, 2026, is the last day of ISO week 42 (Oct. 12 to 18). Tomorrow starts week 43. If your office counts weeks from Sunday, the U.S. way, today is already the first day of week 43.

How ISO week numbers work

The rule fits on one line: weeks start on Monday, and week 1 is the week that contains the year’s first Thursday. Put another way, week 1 always contains Jan. 4.

In 2027, the first Thursday is Jan. 7, so week 1 runs Jan. 4 to 10. Most years end up with 52 weeks. A year gets a 53rd week when it starts on a Thursday, or when it is a leap year that starts on a Wednesday. 2026 starts on a Thursday, which is why it has 53. After 2026, the next 53-week year is 2032.

YearStarts onISO weeksWeek 1 begins
2026Thursday53Monday, Dec. 29, 2025
2027Friday52Monday, Jan. 4, 2027
2028Saturday52Monday, Jan. 3, 2028

Europe uses this system, and so does most business and scheduling software outside the United States. It is also what calendar apps show when you turn on week numbers with a Monday start.

The U.S. system gives different numbers

Many American calendars, and Excel’s default WEEKNUM function, count weeks differently. Weeks start on Sunday, and week 1 is simply the week that contains Jan. 1, however short it is. In 2027 that first week is just two days long (Friday, Jan. 1 and Saturday, Jan. 2). Week 2 starts Sunday, Jan. 3.

So the two systems disagree for nearly the whole year. Thursday, Nov. 25, 2027 (Thanksgiving) is ISO week 47 but U.S. week 48. The U.S. count also runs to week 53, ending with the six days from Sunday, Dec. 26 to Friday, Dec. 31. When a colleague in another country mentions “week 12,” check which system they mean.

2027 week numbers by month

MonthISO weeks (Monday start)First Monday
JanuaryW53 of 2026, then W01 to W04Jan. 4 (W01)
FebruaryW05 to W08Feb. 1 (W05)
MarchW09 to W13March 1 (W09)
AprilW13 to W17April 5 (W14)
MayW17 to W22May 3 (W18)
JuneW22 to W26June 7 (W23)
JulyW26 to W30July 5 (W27)
AugustW30 to W35Aug. 2 (W31)
SeptemberW35 to W39Sept. 6 (W36)
OctoberW39 to W43Oct. 4 (W40)
NovemberW44 to W48Nov. 1 (W44)
DecemberW48 to W52Dec. 6 (W49)

The week numbers list in the downloads gives the Monday and Sunday of all 52 weeks. For the whole year without week numbers, see our 2027 printable yearly calendar or the Monday-start calendar.

Week numbers of 2027 holidays

HolidayDateISO week
Martin Luther King Jr. DayMonday, Jan. 183
Presidents’ DayMonday, Feb. 157
Memorial DayMonday, May 3122
JuneteenthSaturday, June 1924
Independence DaySunday, July 426
Labor DayMonday, Sept. 636
ThanksgivingThursday, Nov. 2547
Christmas DaySaturday, Dec. 2551

Four of these fall on a weekend in 2027. Federal offices observe Juneteenth on Friday, June 18, Independence Day on Monday, July 5, and Christmas on Friday, Dec. 24. New Year’s Day 2028 falls on a Saturday, so it is observed on Friday, Dec. 31, 2027.

Week numbers in Excel and Google Sheets

FormulaSystemResult for Jan. 1, 2027
=ISOWEEKNUM(A1)ISO 860153
=WEEKNUM(A1,21)ISO 8601 (Excel only)53
=WEEKNUM(A1)U.S., Sunday start1
=WEEKNUM(A1,2)Monday start, week of Jan. 1 is week 11

Microsoft documents ISOWEEKNUM and the WEEKNUM return types on its support site, and Google Sheets supports the same ISOWEEKNUM function. If a report shows a week number that is one higher than your wall calendar, the formula is probably the plain WEEKNUM.

Planning with week numbers

Week numbers help with school terms, sprint planning, payroll and shipping schedules, where “week 14” is shorter than a date range. A 52-week year also lines up neatly with four 13-week quarters, the pattern many retail and fiscal calendars follow; our fiscal year calendar guide explains those layouts. For day-by-day planning, pair the week number calendar with a printable weekly planner, and for day-of-year numbers see our Julian date calendar.

Frequently asked questions

What week number is it today?

Sunday, Oct. 18, 2026, is the last day of ISO week 42, which runs Monday, Oct. 12 to Sunday, Oct. 18. Under the U.S. Sunday-start system it is the first day of week 43.

When does week 1 of 2027 start?

Monday, Jan. 4, 2027, under ISO 8601. Week 1 is the week that contains the year's first Thursday, and in 2027 that Thursday is Jan. 7.

How many weeks are in 2027?

52 ISO weeks. The last one, week 52, runs from Monday, Dec. 27, 2027 to Sunday, Jan. 2, 2028. Counted the U.S. way, the year reaches week 53.

Does 2026 have 53 weeks?

Yes. 2026 starts on a Thursday, so it has 53 ISO weeks. Week 53 runs from Monday, Dec. 28, 2026 to Sunday, Jan. 3, 2027. The next 53-week year after that is 2032.

What week number is Christmas 2027?

Saturday, Dec. 25, 2027 falls in ISO week 51 (Dec. 20 to 26). Thanksgiving, Thursday, Nov. 25, is in week 47.

How do I get the ISO week number in Excel or Google Sheets?

Use =ISOWEEKNUM(A1), where A1 holds the date. Plain =WEEKNUM(A1) uses the U.S. Sunday-start system instead and can return a different number.

Sources

  1. ISO 8601 Date and time format (International Organization for Standardization)
  2. ISOWEEKNUM function (Microsoft Support)
  3. WEEKNUM function (Microsoft Support)
  4. ISOWEEKNUM (Google Docs Editors Help)