Add Days Calculator

Add days to a date using the day addition calculator below. You can subtract days from a date by making the days negative.


Learn how we calculated this below

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How to Add Days to a Date

Whether you’re calculating a project’s deadline, counting the days until a special event, or managing scheduling tasks, knowing how to add some number of days to a date is a valuable skill. You can use a few different methods to calculate what the date will be after adding any number of days.

Method One: Add Days Manually

The first way to add a specified number of days to a date is to add them manually. You can start by adding the number of days to the day number portion of the starting date. If the sum of these days is less than the number of days in that month, then that’s the resulting date.

If the sum of the days is greater than the number of days in the month, then you’ll need to use a calendar. Locate the starting date on the calendar, then move forward one day for each of the number of days you want to add.

When you reach the end of a month, continue into the next month.

This method works well for adding small numbers of days, but as the number of days grows, the process gets more tedious. For instance, adding 7 days to today is fairly quick using this method, but if you want to add 90 days, then this method can be a bit unwieldy and time-consuming.

Method Two: Add Days With Spreadsheet Software

You can also add any number of days to a date using software such as Microsoft Excel or Google Sheets. This method is as easy as adding any two numbers together.

Start by entering the start date in cell A1. Then, in another cell, enter the following formula to add 90 days to that date:

=A1 + 90

This will add 90 days to the date in cell A1 and produce the resulting date in the cell in which you typed the formula. Of course, you can change the value of 90 to any other number of days you want to add, or specify a start date in any cell you want instead of using A1.

Method Three: Add Days Using an Online Calculator

We have several calculators available that allow you to add or subtract any number of days from a specific date, such as our days from today calculator or the calculator above. We also have a calculator that allows you to add hours, minutes, and seconds.