📆 Week of the Month Calculator
By ToolNimba Editorial Team · Updated 2026-06-19
Pick a date and choose which weekday starts the week.
This week of the month calculator tells you which week of the month any date falls in, from the 1st week through to the 5th or 6th. Enter a date, choose whether your weeks start on Sunday or Monday, and you will see the week number along with the exact date range that week covers. It is handy for payroll cycles, rota planning, recurring meetings, and any schedule that runs in weekly blocks within a month.
What is the Week of the Month Calculator?
The week of the month is simply the position of a given week inside its calendar month, counted from the start of the month. Unlike the ISO week number (which counts weeks across the whole year), this is a local count: the month always begins with week 1 and the count resets to 1 on the 1st of every month. Most months span five distinct weeks, and a few span six, depending on which weekday the 1st lands on and how long the month is.
The one detail that changes the answer is where you draw the line between one week and the next. There is no single global standard. In the United States and much of Asia the week is commonly treated as starting on Sunday, while in the United Kingdom, Europe, and the ISO standard the week starts on Monday. Because the boundary moves, the same date can sit in a different week number under each convention, so this tool lets you choose the week start that matches your calendar.
The method used here is the most widely understood one: week 1 always contains the 1st of the month, and the week number increases by one every time the chosen start weekday comes around. So under a Sunday start, the first Sunday on or after the 1st begins week 2, the next Sunday begins week 3, and so on. The calculator also reports the date range of the week your date belongs to, clamped to the month so it never spills into the previous or next month.
When to use it
- Working out which week of the month a payroll run, invoice, or rent payment falls in.
- Scheduling a recurring meeting like "the 3rd week of every month" and confirming the dates.
- Planning a staff rota or shift pattern that resets at the start of each month.
- Tagging blog posts, reports, or social content by the week of the month they were published.
How to use the Week of the Month Calculator
- Enter the date you want to check, or click Use today.
- Choose whether your weeks start on Sunday or Monday.
- Read off the week of the month (1st, 2nd, 3rd, and so on).
- Check the date range below it to see the full span of that week within the month.
Formula & method
Worked examples
What week of the month is 19 June 2026, with weeks starting on Sunday?
- 1 June 2026 is a Monday, so the weekday of the 1st is 1 (Sunday = 0).
- offset = (1 − 0 + 7) mod 7 = 1
- week = floor((19 + 1 − 1) ÷ 7) + 1 = floor(19 ÷ 7) + 1 = 2 + 1 = 3
Result: 3rd week of June, running Sunday 14 June to Saturday 20 June.
What week of the month is 8 June 2026, with weeks starting on Monday?
- 1 June 2026 is a Monday, so with a Monday start the offset is (1 − 1 + 7) mod 7 = 0.
- week = floor((8 + 0 − 1) ÷ 7) + 1 = floor(7 ÷ 7) + 1 = 1 + 1 = 2
- The 1st to 7th make up week 1, so the 8th opens week 2.
Result: 2nd week of June, running Monday 8 June to Sunday 14 June.
How a Sunday start and a Monday start can label the same dates differently (June 2026, where the 1st is a Monday)
| Date | Week (Sunday start) | Week (Monday start) |
|---|---|---|
| 1 June (Mon) | 1 | 1 |
| 6 June (Sat) | 1 | 1 |
| 7 June (Sun) | 2 | 1 |
| 8 June (Mon) | 2 | 2 |
| 30 June (Tue) | 5 | 5 |
Common week-start conventions by region
| Convention | Week starts on | Where it is used |
|---|---|---|
| United States, Canada, Japan | Sunday | Most consumer calendars and payroll |
| ISO 8601, UK, most of Europe | Monday | Business, government, ISO week numbers |
| Middle East (some countries) | Saturday | Local working-week calendars |
Common mistakes to avoid
- Confusing week of the month with the ISO week of the year. The week of the month resets to 1 on the 1st of each month. The ISO week number runs 1 to 52 or 53 across the whole year, so the two will almost never match. Use the right one for your task.
- Forgetting that the week start changes the answer. A date can be in week 2 under a Sunday start but week 1 under a Monday start. Always set the week start to match the calendar your schedule actually uses before reading the result.
- Assuming every month has exactly four weeks. A month is roughly 4.3 weeks long, so most months show five week numbers and some show six. A pay period billed as "4 weeks" is not the same as a calendar month.
Glossary
- Week of the month
- The position of a week inside its calendar month, counted from week 1 (which contains the 1st) onward, resetting each month.
- Week start
- The weekday treated as the first day of each week, usually Sunday or Monday. It sets where one week ends and the next begins.
- ISO week number
- A year-wide week count (1 to 53) defined by ISO 8601, where weeks start on Monday and week 1 holds the year first Thursday. Different from week of the month.
- Week range
- The span of dates covered by a given week, here clamped to the month so the first and last weeks may be shorter than seven days.
Frequently asked questions
How is the week of the month calculated?
Week 1 always contains the 1st of the month, and the count rises by one each time your chosen start weekday (Sunday or Monday) comes around. The formula is week = floor((day of month + offset − 1) ÷ 7) + 1, where offset is how far the 1st sits past the most recent week-start day.
Does the week start on Sunday or Monday?
It depends on your region. The United States and much of Asia start the week on Sunday, while the UK, Europe, and the ISO standard start on Monday. This tool lets you pick either, because the choice can change the week number for some dates.
Can a month have six weeks?
Yes. A month spans six week numbers when the 1st falls late in the week and the month is long enough. For example a 31-day month whose 1st lands on a Friday or Saturday under a Sunday start will reach into a 6th week.
Is the week of the month the same as the ISO week number?
No. The week of the month resets to 1 on the 1st of every month and only counts within that month. The ISO week number counts weeks across the entire year from 1 to 52 or 53, so the two values are almost always different.
Why does the first or last week look shorter than seven days?
The week range is clamped to the month. If a week began in the previous month or runs into the next one, only the days inside the current month are shown, so the first and last weeks can be shorter than a full seven days.
What week of the month is it today?
Click Use today and the calculator fills in the current date, then shows which week of the month it falls in for your chosen week start, along with that week date range.