WhatWeek

2027 Calendar with Week Numbers

View ISO week numbers, US-style comparison, week date ranges, and month calendars for 2027.

ISO weeks in 2027

52

12-month calendar view

Scan the year by quarter, month, and ISO week before opening the full data table below.

Year atlas

2027 mapped across 52 ISO weeks

Scan the year by week, quarter, and month. The ribbon marks the current ISO week and makes the full ISO year visible before you dive into each month.

ISO year length

52

Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14 Week 15 Week 16 Week 17 Week 18 Week 19 Week 20 Week 21 Week 22 Week 23 Week 24 Week 25 Week 26 Week 27 Week 28 Week 29 Week 30 Week 31 Week 32 Week 33 Week 34 Week 35 Week 36 Week 37 Week 38 Week 39 Week 40 Week 41 Week 42 Week 43 Week 44 Week 45 Week 46 Week 47 Week 48 Week 49 Week 50 Week 51 Week 52
W1 Quarter start
W1 quarter start Current week

Q1

W1-W13

Jan · Feb · Mar

Includes Week 53

Q2

W13-W26

Apr · May · Jun

Q3

W26-W39

Jul · Aug · Sep

Q4

W39-W52

Oct · Nov · Dec

Quarter 1

Q1 planning view

W1-W13

Q1

January

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
53
1
2
3
4
5

Q1

February

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
5
6
7
8
9
10

Q1

March

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
9
10
11
12
13
14

Quarter 2

Q2 planning view

W13-W26

Q2

April

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
13
14
15
16
17
18

Q2

May

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
17
18
19
20
21
22

Q2

June

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
22
23
24
25
26
27

Quarter 3

Q3 planning view

W26-W39

Q3

July

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
26
27
28
29
30
31

Q3

August

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
30
31
32
33
34
35

Q3

September

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
35
36
37
38
39
40

Quarter 4

Q4 planning view

W39-W52

Q4

October

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
39
40
41
42
43
44

Q4

November

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
44
45
46
47
48
49

Q4

December

Wk
Mon
Tue
Wed
Thu
Fri
Sat
Sun
48
49
50
51
52
1

ISO vs US-style week comparison

ISO weeks start on Monday and Week 1 contains January 4. The simplified US-style week shown here starts on Sunday and Week 1 contains January 1, so the week number and date range can differ.

Date ISO week ISO range US-style week US-style range
2027-01-01 2026-W53 2026-12-28 to 2027-01-03 Week 1 2026-12-27 to 2027-01-02
2027-05-03 2027-W18 2027-05-03 to 2027-05-09 Week 19 2027-05-02 to 2027-05-08
2027-12-31 2027-W52 2027-12-27 to 2028-01-02 Week 53 2027-12-26 to 2028-01-01

ISO week table

Download CSV Previous year

CSV columns: year, week, system, weekStarts, weekEnds, plus legacy weekday/weekend count fields. Open the CSV in Excel or Google Sheets to sort by week number, filter planning periods, or combine WhatWeek date ranges with your own spreadsheet data.

Week ISO notation Starts Ends Weekdays
Week 1 W01 2027-01-04 2027-01-10 5
Week 2 W02 2027-01-11 2027-01-17 5
Week 3 W03 2027-01-18 2027-01-24 5
Week 4 W04 2027-01-25 2027-01-31 5
Week 5 W05 2027-02-01 2027-02-07 5
Week 6 W06 2027-02-08 2027-02-14 5
Week 7 W07 2027-02-15 2027-02-21 5
Week 8 W08 2027-02-22 2027-02-28 5
Week 9 W09 2027-03-01 2027-03-07 5
Week 10 W10 2027-03-08 2027-03-14 5
Week 11 W11 2027-03-15 2027-03-21 5
Week 12 W12 2027-03-22 2027-03-28 5
Week 13 W13 2027-03-29 2027-04-04 5
Week 14 W14 2027-04-05 2027-04-11 5
Week 15 W15 2027-04-12 2027-04-18 5
Week 16 W16 2027-04-19 2027-04-25 5
Week 17 W17 2027-04-26 2027-05-02 5
Week 18 W18 2027-05-03 2027-05-09 5
Week 19 W19 2027-05-10 2027-05-16 5
Week 20 W20 2027-05-17 2027-05-23 5
Week 21 W21 2027-05-24 2027-05-30 5
Week 22 W22 2027-05-31 2027-06-06 5
Week 23 W23 2027-06-07 2027-06-13 5
Week 24 W24 2027-06-14 2027-06-20 5
Week 25 W25 2027-06-21 2027-06-27 5
Week 26 W26 2027-06-28 2027-07-04 5
Week 27 W27 2027-07-05 2027-07-11 5
Week 28 W28 2027-07-12 2027-07-18 5
Week 29 W29 2027-07-19 2027-07-25 5
Week 30 W30 2027-07-26 2027-08-01 5
Week 31 W31 2027-08-02 2027-08-08 5
Week 32 W32 2027-08-09 2027-08-15 5
Week 33 W33 2027-08-16 2027-08-22 5
Week 34 W34 2027-08-23 2027-08-29 5
Week 35 W35 2027-08-30 2027-09-05 5
Week 36 W36 2027-09-06 2027-09-12 5
Week 37 W37 2027-09-13 2027-09-19 5
Week 38 W38 2027-09-20 2027-09-26 5
Week 39 W39 2027-09-27 2027-10-03 5
Week 40 W40 2027-10-04 2027-10-10 5
Week 41 W41 2027-10-11 2027-10-17 5
Week 42 W42 2027-10-18 2027-10-24 5
Week 43 W43 2027-10-25 2027-10-31 5
Week 44 W44 2027-11-01 2027-11-07 5
Week 45 W45 2027-11-08 2027-11-14 5
Week 46 W46 2027-11-15 2027-11-21 5
Week 47 W47 2027-11-22 2027-11-28 5
Week 48 W48 2027-11-29 2027-12-05 5
Week 49 W49 2027-12-06 2027-12-12 5
Week 50 W50 2027-12-13 2027-12-19 5
Week 51 W51 2027-12-20 2027-12-26 5
Week 52 W52 2027-12-27 2028-01-02 5