Calculating Start Date from Need Date and Duration

[CoriSt]

I am working on an intake form and I have a field for when the item needs to complete (Due Date) and an estimate for how long it will take (Duration Estimate).  Is there a way to calculate when it needs to start based on those two items?  

Thanks,

Cori

[Richard_Le_]

Hi Cori,

You could achieve this with a calculated date field that subtracts the duration estimate from the due date. The calculation would look something like this:

ADDWEEKDAYS({DE:Due Date},-{DE:Duration Estimate})

Best Regards,

Rich.

[CoriSt]

Rich,

I thought it was that simple, but when I try this I get an error that says "ADDDAYS must contain 2 values".

If I remove the minus sign, it tells me that "Due Date" is not valid in this expression.

Any ideas?  I also need to figure out how to convert my Duration into days (it will likely be weeks or months).

Thanks!

Cori

[Richard_Le_ · Accepted solution]

Hi Cori,

What data format is your duration estimate field? It needs to be a number format in order for the calculation to work. My calculation assumes that the duration estimate is a number of days. 

If your users are typing the duration as text (i.e., "3 months"), Workfront wont be able to read this as a number to carry out any mathematical calculations. 

If you can have your users enter the estimated duration consistently as a number, we could update the calculation to accommodate weeks or months. For example, the below code would subtract the number of months specified in the duration estimate from the due date. 

ADDMONTHS({DE:Due Date},-{DE:Duration Estimate})

Best Regards,

Rich. 

[CoriSt]

Thank you!  It's working now.

Cori