Excel - Need formula to calculate subtotal before sales tax

Asked By HLR2007 on 13-Sep-07 11:48 PM
I have a spreadsheet showing a year's worth of invoices that have the
final totals listed, but I need a formula to show the subtotal before
the sales tax is added.

The example I am working from has me very frustrated, to say the
least.  I feel REALLY dumb right about now!

Subtotal of Order = $253
Sales Tax = 8.75%
Final Total = $275.14

So, my year summary already shows the total ($275.14) and I need to
calculate and display the subtotal ($253).  I know the subtotal in
this example because I went back and looked at the original invoice,
but I don't want to do that every time.

I won't even bother including my formulas, as I already know they are

David Hilberg replied on 14-Sep-07 12:30 AM
Divide Total by 1.0875.

- David
pdberge replied on 14-Sep-07 12:34 AM
HLR --

Howze about:

A              B
1     $275.14     =A1/1.0875

seems to work.  Answer is $253.0023

joeu2004 replied on 14-Sep-07 12:56 AM
Ostensibly, if the final total is in B3 and the sales tax rate in B2,
then subtotal in B1 can be computed by:

=round(B3/(1+B2), 2)

But I don't know if that will always reproduce the original subtotal
exactly.  You see, originally the final total (B3) was computed
effectively by:

=B1 + round(B1*B2, 2)

But it seems to work for all the (random) numbers that I have tried.
HLR2007 replied on 14-Sep-07 11:28 PM
This one works perfectly!  Thanks so much.