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Weeks Calculator

Weeks and days between two dates, the date N weeks from today, and today's week number.

Last updated: 2026/10/17 Calculator Feedback & bug reports
–weeks–days
 
 
Common periods

This week

ISO week number–
Week number (US)–
Week of the month–
Left this year–

To look up the week number of another date, or the dates of a given week number, use the Week Number Calculator.

Weeks chart

Tap a number of weeks to see that date from today in the calculator above.

WeeksDaysFrom today
7 days≈ 0.2 mo
14 days≈ 0.5 mo
21 days≈ 0.7 mo
28 days≈ 0.9 mo
35 days≈ 1.1 mo
42 days≈ 1.4 mo
56 days≈ 1.8 mo
70 days≈ 2.3 mo
84 days≈ 2.8 mo
91 days≈ 3.0 mo
112 days≈ 3.7 mo
140 days≈ 4.6 mo
168 days≈ 5.5 mo
182 days≈ 6.0 mo
210 days≈ 6.9 mo
252 days≈ 8.3 mo
280 days≈ 9.2 mo
364 days≈ 12.0 mo

“≈ N mo” uses an average month of 30.44 days (365.2425 ÷ 12). A month averages about 4.35 weeks (365.2425 ÷ 12 ÷ 7 ≈ 4.348), but real months vary: February is exactly 4 weeks in a common year, and a 31-day month is 4 weeks and 3 days.

To convert between days, weeks, months and years, use the Time Period Converter.

How to Use

1

Choose what to calculate

Use “Between two dates” to count the weeks and days between dates, or “Weeks from a date” to find the date a number of weeks later or earlier. When the page opens, it already shows the weeks since January 1 of this year.

2

Enter dates or tap a shortcut

Enter a start date and an end date and the result appears instantly. Shortcuts such as “Since Jan 1”, “Until Christmas” and “School year” fill in common periods in one tap, and you can still edit the dates.

3

Check and copy the result

Along with weeks and days you get the total days, decimal weeks, fortnights, and months and days. Use “Copy result” to paste it anywhere. The “This week” panel shows today's week number and the weeks left this year.

What is the Weeks Calculator?

A calculator that counts how many weeks and days lie between two dates. Common periods such as since January 1, until December 31, until Christmas and the school year take one tap, and you can also find the date a number of weeks from any date. It shows today's week number (ISO and US style) and how many weeks are left this year. Everything runs in your browser; your dates are never sent anywhere.

Features

  • Answer at a glanceThe weeks since January 1 appear as soon as the page opens, and the result updates the moment you change a date.
  • One-tap shortcutsSince Jan 1, until Dec 31, until Christmas, the school year, or 1 to 52 weeks from today, with custom values too.
  • Today's week numberISO and US week numbers, the week of the month, and the weeks left this year.
  • Weeks, days and fortnightsSee weeks and days, total days, decimal weeks, fortnights, and months and days together.

Use Cases

  • Planning a project or a training program in weeks
  • Counting the weeks until an exam, a trip or Christmas
  • Checking how many weeks are in the school year
  • Finding the date 6, 8 or 12 weeks from today
  • Looking up today's week number for reports and timesheets

Related date tools

To count days, months and years between dates or business days in one place, use the Date Calculator. For the date a number of days from today, try the Days From Date Calculator; for week numbers, the Week Number Calculator; for pregnancy weeks and a due date, the Due Date Calculator; and to convert weeks into months or days into years, the Time Period Converter. The basics of counting dates are explained in our guide to date and day calculations.

FAQ

How do you calculate the weeks between two dates?
The number of days from the start date to the end date is divided by 7: the quotient is the weeks and the remainder is the days. For example, January 1 to March 1 in a common year is 59 days, and 59 ÷ 7 = 8 remainder 3, so the answer is 8 weeks and 3 days (about 8.43 weeks). Leap years and month lengths are handled automatically.
What does “Include the start date” change?
It counts the start date as day 1, so the total grows by one day. From January 1 to January 8 is 7 days (1 week) without it and 8 days (1 week 1 day) with it. Leave it off to measure how far apart two dates are; turn it on for schedules where both the first and last days count, such as a course or a trip.
What week of the year is it today?
The “This week” panel shows both the ISO 8601 week number (weeks start on Monday and week 1 contains January 4) and the US-style number (weeks start on Sunday and the week containing January 1 is week 1, like Excel's WEEKNUM default). Around New Year the two systems can differ. To check another date or turn a week number back into dates, use the Week Number Calculator.
How many weeks are left this year?
“Left this year” in the “This week” panel counts from today to December 31, not counting today. Tap “Until Dec 31” to see the same calculation in the calculator with weeks, days and fortnights.
How many weeks are in a school year?
From September 1 to June 30 is 302 days, or 43 weeks and 1 day (303 days, 43 weeks and 2 days, when the school year includes February 29). Tap “School year” and adjust the dates to your own calendar. Breaks are not removed, so the number of teaching weeks is smaller; many US schools have about 180 instructional days, or 36 weeks.
How many weeks until Christmas?
Tap “Until Christmas”. The calculator counts from today to December 25 (next year's Christmas once this year's has passed) and shows the weeks and days, the total days and the fortnights.
How many weeks are in a month?
Between 4 weeks (February in a common year) and 4 weeks and 3 days (31-day months). On average a month is about 4.35 weeks: 365.2425 days ÷ 12 months ÷ 7 days ≈ 4.348 weeks. The weeks chart below gives rough month equivalents, and the Time Period Converter converts between days, weeks, months and years.
Is this the same as counting pregnancy weeks?
Pregnancy is counted from the first day of the last menstrual period, which is week 0 day 0. Set that day as the start date, today as the end date, and leave “Include the start date” off to get the same count (100 days later is 14 weeks 2 days). A due date is 40 weeks 0 days, or 280 days after that start. For the due date and trimesters, use the Due Date Calculator, and always rely on your doctor for medical decisions.
Can I skip weekends and count only business days?
This calculator counts calendar days, weekends and holidays included. To count business days or find a date N business days away, use the Business Day Calculator (it follows Japanese public holidays).
Are my dates saved?
No. All calculations run in your browser, and the dates you enter are never sent to or stored on a server.

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Related Guides

How Many Weeks Are in a Month? Days, Weeks, Months and Years Conversion Chart A month is about 4.35 weeks (4 weeks and 2–3 days). See the math, weeks per month and per year, 1,000 days in years and months, plus easy conversion charts. Date & Day Calculations: Elapsed Days, Business Days, Days From Now A clear guide to counting days between two dates, business days (excluding holidays), a date N days before or after, and weeks. Learn leap-year and endpoint cautions, plus uses for deadline management and anniversaries. What Is an ISO Week Number? How to Count Weeks Under ISO 8601 A beginner-friendly guide to ISO 8601 week numbers: the rule that weeks start on Monday and the week containing the first Thursday is week 1, how to find the nth week, how it differs from "the nth week of the month," and how to use it in work calendars and project management.