Weeks Calculator

Q: How many days are in a week?

There are 7 days in a week. A week runs from Sunday through Saturday or Monday through Sunday, depending on your region. This calculator uses 7 days per week for all standard calculations and 5 days per week when you turn on business weeks.

Q: What is a business week?

A business week is 5 days , Monday through Friday. It skips Saturday and Sunday. Turn on the "Count business weeks only" toggle in the calculator to use business weeks instead of full 7-day weeks.

Q: How many weeks are in a year?

A regular year has 52 weeks and 1 day (365 days). A leap year has 52 weeks and 2 days (366 days). So there are always slightly more than 52 weeks in any year.

Q: How many weeks are in a month?

Most months have about 4 weeks and 2 or 3 extra days . February in a non-leap year has exactly 4 weeks. No other month is exactly divisible by 7, so the count is always a little more than 4.

Q: What does the donut chart show?

The donut chart splits your time span into weekdays (Monday–Friday) and weekend days (Saturday–Sunday). It shows both the count and the percentage so you can see how much of your span falls on working days versus weekends.

Q: How do I find a date that is a certain number of weeks from today?

Select Add Weeks mode, click the Today button for the start date, and type the number of weeks. The calculator will show you the exact future date. Use Subtract Weeks mode to go backward instead.

Weeks Calculator

Updated Jun 18, 2026 By Jehan Wadia

Introduction

The Weeks Calculator helps you work with weeks and dates in three simple ways. You can find the number of weeks between two dates, add weeks to a date, or subtract weeks from a date. It works with both regular weeks and business weeks, so you can skip weekends when you need to.

Just pick a mode, enter your dates or a number of weeks, and hit Calculate. The tool gives you a clear breakdown of weeks, days, and months. It also shows a chart that splits your time span into weekdays and weekend days. Whether you are planning a project, tracking a deadline, or counting down to an event, this calculator does the math for you in seconds.

How to Use Our Weeks Calculator

Enter your dates or week values below to find the number of weeks between two dates, or to add or subtract weeks from a date. The calculator will show you the result in weeks, days, and months.

Calculation Mode: Pick how you want to calculate. Choose "Weeks Between" to find the time between two dates. Choose "Add Weeks" to find a future date. Choose "Subtract Weeks" to find a past date.

Start Date: Enter your starting date or click the "Today" button to use today's date.

End Date: Enter your ending date when using "Weeks Between" mode. You can click "Swap" to switch the start and end dates.

Number of Weeks: When using "Add Weeks" or "Subtract Weeks" mode, type the number of weeks you want to add or subtract. You can use partial weeks like 2.5.

Count business weeks only: Turn this on to skip weekends and only count Monday through Friday. If you need to count only working days without the week grouping, try our Business Days Calculator.

Count the end date: Turn this on to include the end date in your total count.

Show as decimal weeks: Turn this on to see your result as a decimal number instead of weeks and days.

Click Calculate to see your results. Click Clear to reset all fields and start over.

How to Calculate Weeks Between Dates

A week is a unit of time equal to 7 days. We use weeks to plan school terms, track pregnancies, schedule projects, and measure how long until an event. This weeks calculator helps you work with weeks in three simple ways.

Weeks Between Two Dates

Pick a start date and an end date, and the calculator counts the total number of weeks and days between them. For example, if two dates are 20 days apart, the result is 2 weeks and 6 days. You can also turn on the inclusive option to count the end date as part of the total. This is useful when both the first and last day matter, like the start and end of a vacation. For a broader look at the full duration between two dates in years, months, and days, our Date Duration Calculator can help.

Add or Subtract Weeks from a Date

Start with any date and add or subtract a set number of weeks. The calculator gives you the exact resulting date. You can even use partial weeks like 2.5 to add 17 or 18 days. This is handy for finding due dates, deadlines, or planning ahead. If you need to add or subtract other time units like days or months, check out our Date Calculator.

Business Weeks

A business week counts only the 5 weekdays from Monday through Friday. Turn on the business weeks option to skip weekends in every calculation. This is helpful for work schedules, project timelines, and shipping estimates where weekends do not count. If you are tracking hours worked during those business days, our Work Hours Calculator and Time Card Calculator are useful companions.

Extra Details

Along with the main result, the calculator shows total days, total months, and a decimal week value. A decimal week uses numbers after the dot to show partial weeks. For instance, 10 days is about 1.43 weeks. A donut chart also breaks down how many of the days in your span fall on weekdays versus weekend days, so you can see the split at a glance. For other time-related math like finding the difference between two clock times, see our Time Difference Calculator or the general-purpose Time Calculator. You can also use the Days Until Calculator to count down to an upcoming event or the Age Calculator to find someone's exact age in years, months, and weeks.

Frequently asked questions

How many days are in a week?

There are 7 days in a week. A week runs from Sunday through Saturday or Monday through Sunday, depending on your region. This calculator uses 7 days per week for all standard calculations and 5 days per week when you turn on business weeks.

What is a business week?

A business week is 5 days, Monday through Friday. It skips Saturday and Sunday. Turn on the "Count business weeks only" toggle in the calculator to use business weeks instead of full 7-day weeks.

What does the inclusive option do?

The inclusive option adds the end date to your count. Without it, the calculator counts the days between the two dates. With it on, the end date itself is included. For example, Monday to Friday is 4 days normally but 5 days with inclusive counting.

Can I use partial weeks like 2.5?

Yes. In Add Weeks or Subtract Weeks mode, you can type a decimal number like 2.5. The calculator multiplies by 7 (or 5 for business weeks) and rounds to get the exact number of days. So 2.5 regular weeks equals 18 days.

What does decimal weeks mean?

Decimal weeks show your result as a single number with a decimal point instead of whole weeks and leftover days. For example, 10 days is 1.43 weeks instead of 1 week and 3 days. Turn on the "Show primary result as decimal weeks" toggle to see this.

Does the order of the dates matter?

No. You can enter the dates in any order. The calculator always finds the gap between them. If you want to switch them, click the Swap button to flip the start and end dates.

How many weeks are in a year?

A regular year has 52 weeks and 1 day (365 days). A leap year has 52 weeks and 2 days (366 days). So there are always slightly more than 52 weeks in any year.

How many weeks are in a month?

Most months have about 4 weeks and 2 or 3 extra days. February in a non-leap year has exactly 4 weeks. No other month is exactly divisible by 7, so the count is always a little more than 4.

What does the donut chart show?

The donut chart splits your time span into weekdays (Monday–Friday) and weekend days (Saturday–Sunday). It shows both the count and the percentage so you can see how much of your span falls on working days versus weekends.

How do I find a date that is a certain number of weeks from today?

Select Add Weeks mode, click the Today button for the start date, and type the number of weeks. The calculator will show you the exact future date. Use Subtract Weeks mode to go backward instead.

Does this calculator account for time zones or daylight saving time?

No. The calculator works with calendar dates only. It does not factor in time zones, daylight saving changes, or clock times. Every day is treated as a full 24-hour period.

Does the calculator skip holidays in business week mode?

No. Business week mode only skips Saturdays and Sundays. Public holidays that fall on weekdays are still counted. If you need to exclude specific holidays, you will have to subtract those days from the result yourself.

How do I count the weeks of pregnancy?

Use Weeks Between mode. Set the start date to the first day of the last menstrual period and the end date to today. The result in weeks and days gives you the current pregnancy week. A full-term pregnancy is about 40 weeks.

Can I calculate weeks between dates in different years?

Yes. The calculator works across any range of years. You can find weeks between dates that are days apart or many years apart. There is no limit on how far apart the two dates can be.