Do you just need the result of your calculations, and can leave the formula where it is?
1. Copy the Cells you want
2. Right Click where you want to paste the cells and select Paste Special
3. Select the Values radio button
This comes in handy once in a blue moon. You can also check Skip Blanks to do just that.
1. Enter the value you wish to Add, Subtract, Multiply, or Divide by in an empty cell
2. Right-click the cell you just used, and select Copy
3. Select the range you wish to Add, Subtract, Multiply, or Divide by
4. Right-click this range and select Paste Special
5. In the Operations section select your required operation
You can delete the original cell, this does not leave a reference to it