Try these.
1. When entering the number, put a minus sign in front of it.
2. If your positivie number is in cell A1, enter =-a1 in, say cell b1.
3. If you have a group of mixed numbers (positive and negative), use an IF
statement in cell b1. E.g. =if(a1=0,a1,-a1) and copy.

"MICHALK" wrote:

How to change a positive number to negative?