Subtracting 2 time fields

[Gman]

I'm using MySQL version 5.5.25a

I need to get the total time difference from startTime and endTime

So if I have
startTime = 14:00
endTime = 15:30

I need the result to show as 1.5

I believe I am on the right track just not sure how to show the result as I need it...

The fields are TIMESTAMP

SELECT
    TIME_FORMAT(SEC_TO_TIME(UNIX_TIMESTAMP(endTime) - UNIX_TIMESTAMP(startTime)), '%H.%i') AS totalTime
FROM
    table

Right now my result would be 01.30

Thanks

[r937]

SELECT ROUND(( TIME_TO_SEC(endtime) - 
               TIME_TO_SEC(starttime) ) / 3600.0 , 2 )  AS hours_diff

[Gman]

Thanks Rudy, works great.

However I failed to mention this when I posted, what do you think is the best way to do this?

If my timestamp field for startTime is:
2012-08-01 9:00:00

and my endTime field is:
2012-08-02 13:00:00

What would be the way to have MySQL calculate the time difference between the 2 days, because right now if I use the query it returns: -0.98 instead of 28.0

Thanks again and sorry for not posting that vital info...

[Gman]

OK, for some reason it's working now... lol

thanks again!