# Forumla to calculate the percentage (%) change between two dates

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Here, I am seeking to capture the % change between original finish date vs actual finish date.

Example dates are as such:

Original Finish Date = 3/1/23

Actual Finish Date = 4/15/23

What is the percentage change in the date difference? I would like to calculate this to speak to owners of task saying "hey, you deviate from original completion dates by __ % & overall on average __% of the time."

I have attempted to utilized the follow to try calculating the % change between dates but have had no luck as example:

```=((B2-A2)/A2)*100

& =IFERROR(((DATEVALUE(B2)-DATEVALUE(A2))/DATEVALUE(A2))*100,"Invalid Date Format")

```

Smartsheet continues to give me an invalid return OR #UNPARSABLE return.

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Are you able to provide screenshots?

• edited 03/27/23
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@Paul Newcome Here is a screenshot of my actions:

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So basically you want to take the original duration and calculate the variation based on the new duration? Are they both using the same start date?

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