# Calculate Delivery Date Based on Scope Estimate and Workdays?

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4 - Data Explorer

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!

9 Replies 9
4 - Data Explorer

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

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

16 - Uranus

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

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

5 - Automation Enthusiast

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!

16 - Uranus

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

5 - Automation Enthusiast

THANK YOU so much! This is awesome.

4 - Data Explorer

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

16 - Uranus

^ 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.

4 - Data Explorer

Really hoping you all can help me figure out what I’m doing wrong!

I am trying to use a Rollup to calculate my estimated days (summing the estimated times for the tasks that are associated with that project), and referring to THAT in my due-date formula.

I’m using columns which are called:
– Kickoff date
– Time estimate Rollup (which is pulling estimated times from my Tasks table)
– Calc. Due Date

In that Calc. Due Date columns, I’m using the formula: IF({Kickoff date},WORKDAY({Kickoff date},{Time estimate Rollup}, ‘days’))

When I save, I get an Error in each row that has rolled up dates. In records that don’t have rolled up dates, the formula seems to work of course! Pic attached.

What am I doing wrong?

16 - Uranus

You’re confusing the format for `WORKDAY()` with the one for `DATEADD()`. `WORKDAY()` only requires two arguments, and if there is a third argument it would be a list of holidays to exclude from the calculation. Notice how all the examples above are written. Get rid of the `, 'days'` bit from your formula.