Estimating when it's done in excel

Question

Can I, somehow, based on time stamp and how much is done, estimate time and date for when a job is complete? I got this log that a bot I've made writes in column A time [yyy-mm-dd hh:mm], and in column B it wrights how much is done. It sorts it all with newest on top.

Answer 1

Gary's answer is correct, but for convenience if the 2nd row of data can be an arbitrary progress status (not just start of task = implicitly 0%), and if you use percentage number format (or decimals) and you would like to get the end date instead of just the duration, use following formula:

=A1+(A1-A2)/(B1-B2)*(1-B1)

Answer 2

Consider:

In this example the time span is 1 hour and the percent complete in the time span is 78%
Cell C1 contains:

=100-B1

the percent remaining to be done.

In cell D1 is the formula:

=(A1-A2)/B1

D1 yields the time required to complete 1%

Finally in E1:

=D1*C1

the time required to complete the work!
(Note...C1,D1,E1 can be combined into a single formula)

EDIT#1

The formats of E1 and D1 were picked to display the relevent parts of the data
The format of D1,E1 is: mm-dd hh:mm:ss.00

Change this format to suit your needs!