You don't need the sum, and you don't need to multiply by -1, and assuming
that the interest is calculated annually, then

=-(B3*B4)/12

--

HTH

RP
(remove nothere from the email address if mailing direct)


"Ron" wrote in message
...
Hi, is this the correct formula to calculate mortgage interest on an
interest only mortgage?
=SUM((B3*B4)/12)*-1 where B3 is the mortgage and B4 is the interest rate.
Thanks Ron