adding a formula in a cell but when cell = 0 cell is blank

[Guest]

I am trying to create an invoice so when I put qty in cell A1 and the $ value
in cell B1, cell C1 has formula =B1*A1, thats fine, but having that formula
running down C2 C3 C4 etc where there is nothing entered yet, I have $0.00
appearing in each cell, My question is how can I use this formula or
something simular to get same answer to show a blank cell when not used

 

[Bob Phillips]

=IF(AND(A1<>"",B1<>""),B1*A1,"")

 

[Ragdyer]

One way:

=IF(AND(B1>0,A1>0),B1*A1,"")

 

[Aladin Akyurek]

I am trying to create an invoice so when I put qty in cell A1 and the $ value
in cell B1, cell C1 has formula =B1*A1, thats fine, but having that formula
running down C2 C3 C4 etc where there is nothing entered yet, I have $0.00
appearing in each cell, My question is how can I use this formula or
something simular to get same answer to show a blank cell when not used

Custom format the formula cell as e.g.,

[=0]"";General

 

[Guest]

Try
=if(A1*B1=0,"",A1*B1)

 

[Duke Carey]

Aladin -

Better to use a custom format such as

#,##0.00_);(#,##0.00);;

The spot between the second & third semicolons is for the zero format. If
left blank, zeros are suppressed. The last semicolon is for text values.
Since it, too, is blank in my example, no text values would show either

Duke

I am trying to create an invoice so when I put qty in cell A1 and the $
value in cell B1, cell C1 has formula =B1*A1, thats fine, but having that
formula running down C2 C3 C4 etc where there is nothing entered yet, I
have $0.00 appearing in each cell, My question is how can I use this
formula or something simular to get same answer to show a blank cell when
not used

Custom format the formula cell as e.g.,

[=0]"";General