decimal to standard?

You mean decimal notation to standard form ?         (standard form is what the British call scientific notation)

 

0.000456 = 4.56e-4        

 

I just did that by entering it into the web 2.0 calculator

 

If you want to do it by hand here is a video that explains it.

 

http://www.virtualnerd.com/pre-algebra/factors-fractions-exponents/scientific-notation/scientific-notation-examples/scientific-to-decimal-notation-conversion