# Calculate Delivery Date Based on Scope Estimate and Workdays?

Hi Airtable community, formula specialists!

How can I use:

• A fixed start date (e.g. 07/15/2019)
• A #-of-days to execute estimate (e.g. 7)
• WORKDAYS_DIFF()…

to generate an “Est. Delivery Date” that adds a number of days to the start date, treating weekends as “unavailable”?

The acceptance criteria here would be that the forumla returns “07/23/2019” or “07/23/2019 12:00” is fine.

Bonus if the formula can take a decimal rather than an integer for “# Days” for the purpose of supporting half-days. (I’d never get more granular than half-days.)

I’m going to be trying to create this formula myself, but thought the community may want a crack at it, too.

Thanks!

The standard formula that isn’t helpful because it treats weekend days like workdays is:

`IF({Start},DATEADD({Start},{Days},'days'))`

You’re pretty close, you actually need `WORKDAY()` instead of `WORKDAY_DIFF()`

So your formula should be `WORKDAY({Start},{Days})`

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Hi everyone – I’m a total beginner, looking for something similar, but in reverse. I have a DueDate field. Can I generate a StartDate field with a formula that subtracts 14 workdays from the due date? Can the StartDate field be in a date format, so I can see the results in a calendar view? Thanks so much for your help!

Use a negative number: `WORKDAY({DueDate},-14)`. And yes, you can format the result as a date to be used in the calendar.

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THANK YOU so much! This is awesome.

What would the formula be to calculate the date based on days not workdays? many thanks!

^ that’s the “normal” date calculator function. You can replace the field reference `{Days}` in that example with a static number (i.e. 14). All date generation formulas in Airtable accept negative numbers.