I need a formula can you help?

[sjgidman]

Need a bit of Help!
At the mo im make a simple spreadsheet to convert betting odds can do most convert's but when it comes to changing american odds to decimal or fractions i just cant think

to get from fractional to american i use

Fraction to Percentage [=1/(1+D6)] D6=Fraction Cell
then from percentage to american
=IF(D10<0.5,ROUND((100/D10)-100,0),ROUND(-100*D10/(1-D10),0))

D10=Percentage Cell

i just cant get back from american to percentage
Spreadsheet is attached

if you need any more info email [email protected]